Merge pull request #201 from hashicorp/f-resource

High-Level Framework for Writing Providers and Resources

builtin/bins/provider-heroku/main.go

@@ -6,5 +6,5 @@ import (
 )
 
 func main() {
-	plugin.Serve(new(heroku.ResourceProvider))
+	plugin.Serve(new(heroku.Provider()))
 }

builtin/providers/heroku/provider.go

@@ -0,0 +1,45 @@
+package heroku
+
+import (
+	"log"
+
+	"github.com/hashicorp/terraform/helper/schema"
+	"github.com/mitchellh/mapstructure"
+)
+
+// Provider returns a terraform.ResourceProvider.
+func Provider() *schema.Provider {
+	return &schema.Provider{
+		Schema: map[string]*schema.Schema{
+			"email": &schema.Schema{
+				Type:     schema.TypeString,
+				Optional: true,
+			},
+
+			"api_key": &schema.Schema{
+				Type:     schema.TypeString,
+				Optional: true,
+			},
+		},
+
+		ResourcesMap: map[string]*schema.Resource{
+			"heroku_app":    resourceHerokuApp(),
+			"heroku_addon":  resourceHerokuAddon(),
+			"heroku_domain": resourceHerokuDomain(),
+			"heroku_drain":  resourceHerokuDrain(),
+		},
+
+		ConfigureFunc: providerConfigure,
+	}
+}
+
+func providerConfigure(d *schema.ResourceData) (interface{}, error) {
+	var config Config
+	configRaw := d.Get("").(map[string]interface{})
+	if err := mapstructure.Decode(configRaw, &config); err != nil {
+		return nil, err
+	}
+
+	log.Println("[INFO] Initializing Heroku client")
+	return config.Client()
+}

builtin/providers/heroku/provider_test.go

@@ -2,29 +2,35 @@ package heroku
 
 import (
 	"os"
-	"reflect"
 	"testing"
 
+	"github.com/bgentry/heroku-go"
 	"github.com/hashicorp/terraform/config"
+	"github.com/hashicorp/terraform/helper/schema"
 	"github.com/hashicorp/terraform/terraform"
 )
 
 var testAccProviders map[string]terraform.ResourceProvider
-var testAccProvider *ResourceProvider
+var testAccProvider *schema.Provider
 
 func init() {
-	testAccProvider = new(ResourceProvider)
+	testAccProvider = Provider()
 	testAccProviders = map[string]terraform.ResourceProvider{
 		"heroku": testAccProvider,
 	}
 }
 
-func TestResourceProvider_impl(t *testing.T) {
+func TestProvider(t *testing.T) {
-	var _ terraform.ResourceProvider = new(ResourceProvider)
+	if err := Provider().InternalValidate(); err != nil {
+		t.Fatalf("err: %s", err)
+	}
 }
 
-func TestResourceProvider_Configure(t *testing.T) {
+func TestProvider_impl(t *testing.T) {
-	rp := new(ResourceProvider)
+	var _ terraform.ResourceProvider = Provider()
+}
+
+func TestProviderConfigure(t *testing.T) {
 	var expectedKey string
 	var expectedEmail string
 
@@ -50,18 +56,18 @@ func TestResourceProvider_Configure(t *testing.T) {
 		t.Fatalf("err: %s", err)
 	}
 
+	rp := Provider()
 	err = rp.Configure(terraform.NewResourceConfig(rawConfig))
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
 
-	expected := Config{
+	config := rp.Meta().(*heroku.Client)
-		APIKey: expectedKey,
+	if config.Username != expectedEmail {
-		Email:  expectedEmail,
+		t.Fatalf("bad: %#v", config)
 	}
-
+	if config.Password != expectedKey {
-	if !reflect.DeepEqual(rp.Config, expected) {
+		t.Fatalf("bad: %#v", config)
-		t.Fatalf("bad: %#v", rp.Config)
 	}
 }
 

builtin/providers/heroku/resource_heroku_addon.go

@@ -6,9 +6,7 @@ import (
 	"sync"
 
 	"github.com/bgentry/heroku-go"
-	"github.com/hashicorp/terraform/flatmap"
+	"github.com/hashicorp/terraform/helper/schema"
-	"github.com/hashicorp/terraform/helper/config"
-	"github.com/hashicorp/terraform/helper/diff"
 	"github.com/hashicorp/terraform/terraform"
 )
 
@@ -17,163 +15,133 @@ import (
 // multiple addons simultaneously.
 var addonLock sync.Mutex
 
-func resource_heroku_addon_create(
+func resourceHerokuAddon() *schema.Resource {
-	s *terraform.ResourceState,
+	return &schema.Resource{
-	d *terraform.ResourceDiff,
+		Create: resourceHerokuAddonCreate,
-	meta interface{}) (*terraform.ResourceState, error) {
+		Read:   resourceHerokuAddonRead,
+		Update: resourceHerokuAddonUpdate,
+		Delete: resourceHerokuAddonDelete,
+
+		Schema: map[string]*schema.Schema{
+			"app": &schema.Schema{
+				Type:     schema.TypeString,
+				Required: true,
+				ForceNew: true,
+			},
+
+			"plan": &schema.Schema{
+				Type:     schema.TypeString,
+				Required: true,
+			},
+
+			"config": &schema.Schema{
+				Type:     schema.TypeList,
+				Optional: true,
+				ForceNew: true,
+				Elem: &schema.Schema{
+					Type: schema.TypeMap,
+				},
+			},
+
+			"provider_id": &schema.Schema{
+				Type:     schema.TypeString,
+				Computed: true,
+			},
+
+			"config_vars": &schema.Schema{
+				Type:     schema.TypeList,
+				Computed: true,
+				Elem:     &schema.Schema{Type: schema.TypeMap},
+			},
+		},
+	}
+}
+
+func resourceHerokuAddonCreate(d *schema.ResourceData, meta interface{}) error {
 	addonLock.Lock()
 	defer addonLock.Unlock()
 
-	p := meta.(*ResourceProvider)
+	client := meta.(*heroku.Client)
-	client := p.client
 
-	// Merge the diff into the state so that we have all the attributes
+	app := d.Get("app").(string)
-	// properly.
+	plan := d.Get("plan").(string)
-	rs := s.MergeDiff(d)
-
-	app := rs.Attributes["app"]
-	plan := rs.Attributes["plan"]
 	opts := heroku.AddonCreateOpts{}
 
-	if attr, ok := rs.Attributes["config.#"]; ok && attr == "1" {
+	if v := d.Get("config"); v != nil {
-		vs := flatmap.Expand(
-			rs.Attributes, "config").([]interface{})
-
 		config := make(map[string]string)
-		for k, v := range vs[0].(map[string]interface{}) {
+		for _, v := range v.([]interface{}) {
-			config[k] = v.(string)
+			for k, v := range v.(map[string]interface{}) {
+				config[k] = v.(string)
+			}
 		}
 
 		opts.Config = &config
 	}
 
 	log.Printf("[DEBUG] Addon create configuration: %#v, %#v, %#v", app, plan, opts)
-
 	a, err := client.AddonCreate(app, plan, &opts)
-
 	if err != nil {
-		return s, err
+		return err
 	}
 
-	rs.ID = a.Id
+	d.SetId(a.Id)
-	log.Printf("[INFO] Addon ID: %s", rs.ID)
+	log.Printf("[INFO] Addon ID: %s", d.Id())
 
-	addon, err := resource_heroku_addon_retrieve(app, rs.ID, client)
+	return resourceHerokuAddonRead(d, meta)
-	if err != nil {
-		return rs, err
-	}
-
-	return resource_heroku_addon_update_state(rs, addon)
 }
 
-func resource_heroku_addon_update(
+func resourceHerokuAddonRead(d *schema.ResourceData, meta interface{}) error {
-	s *terraform.ResourceState,
+	client := meta.(*heroku.Client)
-	d *terraform.ResourceDiff,
-	meta interface{}) (*terraform.ResourceState, error) {
-	p := meta.(*ResourceProvider)
-	client := p.client
-	rs := s.MergeDiff(d)
-
-	app := rs.Attributes["app"]
-
-	if attr, ok := d.Attributes["plan"]; ok {
-		ad, err := client.AddonUpdate(
-			app, rs.ID,
-			attr.New)
-
-		if err != nil {
-			return s, err
-		}
-
-		// Store the new ID
-		rs.ID = ad.Id
-	}
-
-	addon, err := resource_heroku_addon_retrieve(app, rs.ID, client)
 
+	addon, err := resource_heroku_addon_retrieve(
+		d.Get("app").(string), d.Id(), client)
 	if err != nil {
-		return rs, err
+		return err
 	}
 
-	return resource_heroku_addon_update_state(rs, addon)
+	d.Set("name", addon.Name)
-}
+	d.Set("plan", addon.Plan.Name)
-
+	d.Set("provider_id", addon.ProviderId)
-func resource_heroku_addon_destroy(
+	d.Set("config_vars", []interface{}{addon.ConfigVars})
-	s *terraform.ResourceState,
+	d.SetDependencies([]terraform.ResourceDependency{
-	meta interface{}) error {
+		terraform.ResourceDependency{ID: d.Get("app").(string)},
-	p := meta.(*ResourceProvider)
+	})
-	client := p.client
-
-	log.Printf("[INFO] Deleting Addon: %s", s.ID)
-
-	// Destroy the app
-	err := client.AddonDelete(s.Attributes["app"], s.ID)
-
-	if err != nil {
-		return fmt.Errorf("Error deleting addon: %s", err)
-	}
 
 	return nil
 }
 
-func resource_heroku_addon_refresh(
+func resourceHerokuAddonUpdate(d *schema.ResourceData, meta interface{}) error {
-	s *terraform.ResourceState,
+	client := meta.(*heroku.Client)
-	meta interface{}) (*terraform.ResourceState, error) {
-	p := meta.(*ResourceProvider)
-	client := p.client
 
-	app, err := resource_heroku_addon_retrieve(s.Attributes["app"], s.ID, client)
+	app := d.Get("app").(string)
+
+	if d.HasChange("plan") {
+		ad, err := client.AddonUpdate(
+			app, d.Id(), d.Get("plan").(string))
+		if err != nil {
+			return err
+		}
+
+		// Store the new ID
+		d.SetId(ad.Id)
+	}
+
+	return resourceHerokuAddonRead(d, meta)
+}
+
+func resourceHerokuAddonDelete(d *schema.ResourceData, meta interface{}) error {
+	client := meta.(*heroku.Client)
+
+	log.Printf("[INFO] Deleting Addon: %s", d.Id())
+
+	// Destroy the app
+	err := client.AddonDelete(d.Get("app").(string), d.Id())
 	if err != nil {
-		return nil, err
+		return fmt.Errorf("Error deleting addon: %s", err)
 	}
 
-	return resource_heroku_addon_update_state(s, app)
+	d.SetId("")
-}
+	return nil
-
-func resource_heroku_addon_diff(
-	s *terraform.ResourceState,
-	c *terraform.ResourceConfig,
-	meta interface{}) (*terraform.ResourceDiff, error) {
-
-	b := &diff.ResourceBuilder{
-		Attrs: map[string]diff.AttrType{
-			"app":    diff.AttrTypeCreate,
-			"plan":   diff.AttrTypeUpdate,
-			"config": diff.AttrTypeCreate,
-		},
-
-		ComputedAttrs: []string{
-			"provider_id",
-			"config_vars",
-		},
-	}
-
-	return b.Diff(s, c)
-}
-
-func resource_heroku_addon_update_state(
-	s *terraform.ResourceState,
-	addon *heroku.Addon) (*terraform.ResourceState, error) {
-
-	s.Attributes["name"] = addon.Name
-	s.Attributes["plan"] = addon.Plan.Name
-	s.Attributes["provider_id"] = addon.ProviderId
-
-	toFlatten := make(map[string]interface{})
-
-	if len(addon.ConfigVars) > 0 {
-		toFlatten["config_vars"] = addon.ConfigVars
-	}
-
-	for k, v := range flatmap.Flatten(toFlatten) {
-		s.Attributes[k] = v
-	}
-
-	s.Dependencies = []terraform.ResourceDependency{
-		terraform.ResourceDependency{ID: s.Attributes["app"]},
-	}
-
-	return s, nil
 }
 
 func resource_heroku_addon_retrieve(app string, id string, client *heroku.Client) (*heroku.Addon, error) {
@@ -185,15 +153,3 @@ func resource_heroku_addon_retrieve(app string, id string, client *heroku.Client
 
 	return addon, nil
 }
-
-func resource_heroku_addon_validation() *config.Validator {
-	return &config.Validator{
-		Required: []string{
-			"app",
-			"plan",
-		},
-		Optional: []string{
-			"config.*",
-		},
-	}
-}

builtin/providers/heroku/resource_heroku_addon_test.go

@@ -35,7 +35,7 @@ func TestAccHerokuAddon_Basic(t *testing.T) {
 }
 
 func testAccCheckHerokuAddonDestroy(s *terraform.State) error {
-	client := testAccProvider.client
+	client := testAccProvider.Meta().(*heroku.Client)
 
 	for _, rs := range s.Resources {
 		if rs.Type != "heroku_addon" {
@@ -75,7 +75,7 @@ func testAccCheckHerokuAddonExists(n string, addon *heroku.Addon) resource.TestC
 			return fmt.Errorf("No Addon ID is set")
 		}
 
-		client := testAccProvider.client
+		client := testAccProvider.Meta().(*heroku.Client)
 
 		foundAddon, err := client.AddonInfo(rs.Attributes["app"], rs.ID)
 

builtin/providers/heroku/resource_heroku_app.go

@@ -5,11 +5,8 @@ import (
 	"log"
 
 	"github.com/bgentry/heroku-go"
-	"github.com/hashicorp/terraform/flatmap"
-	"github.com/hashicorp/terraform/helper/config"
-	"github.com/hashicorp/terraform/helper/diff"
 	"github.com/hashicorp/terraform/helper/multierror"
-	"github.com/hashicorp/terraform/terraform"
+	"github.com/hashicorp/terraform/helper/schema"
 )
 
 // type application is used to store all the details of a heroku app
@@ -43,200 +40,167 @@ func (a *application) Update() error {
 	return nil
 }
 
-func resource_heroku_app_create(
+func resourceHerokuApp() *schema.Resource {
-	s *terraform.ResourceState,
+	return &schema.Resource{
-	d *terraform.ResourceDiff,
+		Create: resourceHerokuAppCreate,
-	meta interface{}) (*terraform.ResourceState, error) {
+		Read:   resourceHerokuAppRead,
-	p := meta.(*ResourceProvider)
+		Update: resourceHerokuAppUpdate,
-	client := p.client
+		Delete: resourceHerokuAppDelete,
 
-	// Merge the diff into the state so that we have all the attributes
+		Schema: map[string]*schema.Schema{
-	// properly.
+			"name": &schema.Schema{
-	rs := s.MergeDiff(d)
+				Type:     schema.TypeString,
+				Optional: true,
+				Computed: true,
+			},
+
+			"region": &schema.Schema{
+				Type:     schema.TypeString,
+				Optional: true,
+				Computed: true,
+			},
+
+			"stack": &schema.Schema{
+				Type:     schema.TypeString,
+				Optional: true,
+				Computed: true,
+				ForceNew: true,
+			},
+
+			"config_vars": &schema.Schema{
+				Type:     schema.TypeList,
+				Optional: true,
+				Computed: true,
+				Elem: &schema.Schema{
+					Type: schema.TypeMap,
+				},
+			},
+
+			"git_url": &schema.Schema{
+				Type:     schema.TypeString,
+				Computed: true,
+			},
+
+			"web_url": &schema.Schema{
+				Type:     schema.TypeString,
+				Computed: true,
+			},
+
+			"heroku_hostname": &schema.Schema{
+				Type:     schema.TypeString,
+				Computed: true,
+			},
+		},
+	}
+}
+
+func resourceHerokuAppCreate(d *schema.ResourceData, meta interface{}) error {
+	client := meta.(*heroku.Client)
 
 	// Build up our creation options
 	opts := heroku.AppCreateOpts{}
 
-	if attr := rs.Attributes["name"]; attr != "" {
+	if v := d.Get("name"); v != nil {
-		opts.Name = &attr
+		vs := v.(string)
+		log.Printf("[DEBUG] App name: %s", vs)
+		opts.Name = &vs
+	}
+	if v := d.Get("region"); v != nil {
+		vs := v.(string)
+		log.Printf("[DEBUG] App region: %s", vs)
+		opts.Region = &vs
+	}
+	if v := d.Get("stack"); v != nil {
+		vs := v.(string)
+		log.Printf("[DEBUG] App stack: %s", vs)
+		opts.Stack = &vs
 	}
 
-	if attr := rs.Attributes["region"]; attr != "" {
+	log.Printf("[DEBUG] Creating Heroku app...")
-		opts.Region = &attr
-	}
-
-	if attr := rs.Attributes["stack"]; attr != "" {
-		opts.Stack = &attr
-	}
-
-	log.Printf("[DEBUG] App create configuration: %#v", opts)
-
 	a, err := client.AppCreate(&opts)
 	if err != nil {
-		return s, err
+		return err
 	}
 
-	rs.ID = a.Name
+	d.SetId(a.Name)
-	log.Printf("[INFO] App ID: %s", rs.ID)
+	log.Printf("[INFO] App ID: %s", d.Id())
 
-	if attr, ok := rs.Attributes["config_vars.#"]; ok && attr == "1" {
+	if v := d.Get("config_vars"); v != nil {
-		vs := flatmap.Expand(
+		err = update_config_vars(d.Id(), v.([]interface{}), client)
-			rs.Attributes, "config_vars").([]interface{})
-
-		err = update_config_vars(rs.ID, vs, client)
 		if err != nil {
-			return rs, err
+			return err
 		}
 	}
 
-	app, err := resource_heroku_app_retrieve(rs.ID, client)
+	return resourceHerokuAppRead(d, meta)
-	if err != nil {
-		return rs, err
-	}
-
-	return resource_heroku_app_update_state(rs, app)
 }
 
-func resource_heroku_app_update(
+func resourceHerokuAppRead(d *schema.ResourceData, meta interface{}) error {
-	s *terraform.ResourceState,
+	client := meta.(*heroku.Client)
-	d *terraform.ResourceDiff,
+	app, err := resource_heroku_app_retrieve(d.Id(), client)
-	meta interface{}) (*terraform.ResourceState, error) {
-	p := meta.(*ResourceProvider)
-	client := p.client
-	rs := s.MergeDiff(d)
-
-	if attr, ok := d.Attributes["name"]; ok {
-		opts := heroku.AppUpdateOpts{
-			Name: &attr.New,
-		}
-
-		renamedApp, err := client.AppUpdate(rs.ID, &opts)
-
-		if err != nil {
-			return s, err
-		}
-
-		// Store the new ID
-		rs.ID = renamedApp.Name
-	}
-
-	attr, ok := s.Attributes["config_vars.#"]
-
-	// If the config var block was removed, nuke all config vars
-	if ok && attr == "1" {
-		vs := flatmap.Expand(
-			rs.Attributes, "config_vars").([]interface{})
-
-		err := update_config_vars(rs.ID, vs, client)
-		if err != nil {
-			return rs, err
-		}
-	} else if ok && attr == "0" {
-		log.Println("[INFO] Config vars removed, removing all vars")
-
-		err := update_config_vars(rs.ID, make([]interface{}, 0), client)
-
-		if err != nil {
-			return rs, err
-		}
-	}
-
-	app, err := resource_heroku_app_retrieve(rs.ID, client)
 	if err != nil {
-		return rs, err
+		return err
 	}
 
-	return resource_heroku_app_update_state(rs, app)
+	d.Set("name", app.App.Name)
-}
+	d.Set("stack", app.App.Stack.Name)
+	d.Set("region", app.App.Region.Name)
+	d.Set("git_url", app.App.GitURL)
+	d.Set("web_url", app.App.WebURL)
+	d.Set("config_vars", []map[string]string{app.Vars})
 
-func resource_heroku_app_destroy(
+	// We know that the hostname on heroku will be the name+herokuapp.com
-	s *terraform.ResourceState,
+	// You need this to do things like create DNS CNAME records
-	meta interface{}) error {
+	d.Set("heroku_hostname", fmt.Sprintf("%s.herokuapp.com", app.App.Name))
-	p := meta.(*ResourceProvider)
-	client := p.client
-
-	log.Printf("[INFO] Deleting App: %s", s.ID)
-
-	// Destroy the app
-	err := client.AppDelete(s.ID)
-
-	if err != nil {
-		return fmt.Errorf("Error deleting App: %s", err)
-	}
 
 	return nil
 }
 
-func resource_heroku_app_refresh(
+func resourceHerokuAppUpdate(d *schema.ResourceData, meta interface{}) error {
-	s *terraform.ResourceState,
+	client := meta.(*heroku.Client)
-	meta interface{}) (*terraform.ResourceState, error) {
-	p := meta.(*ResourceProvider)
-	client := p.client
 
-	app, err := resource_heroku_app_retrieve(s.ID, client)
+	// If name changed, update it
+	if d.HasChange("name") {
+		v := d.Get("name").(string)
+		opts := heroku.AppUpdateOpts{
+			Name: &v,
+		}
+
+		renamedApp, err := client.AppUpdate(d.Id(), &opts)
+		if err != nil {
+			return err
+		}
+
+		// Store the new ID
+		d.SetId(renamedApp.Name)
+	}
+
+	// Get the config vars. If we have none, then set it to the empty
+	// list so that they're properly removed.
+	v := d.Get("config_vars")
+	if v == nil {
+		v = []interface{}{}
+	}
+
+	err := update_config_vars(d.Id(), v.([]interface{}), client)
 	if err != nil {
-		return nil, err
+		return err
 	}
 
-	return resource_heroku_app_update_state(s, app)
+	return resourceHerokuAppRead(d, meta)
 }
 
-func resource_heroku_app_diff(
+func resourceHerokuAppDelete(d *schema.ResourceData, meta interface{}) error {
-	s *terraform.ResourceState,
+	client := meta.(*heroku.Client)
-	c *terraform.ResourceConfig,
-	meta interface{}) (*terraform.ResourceDiff, error) {
 
-	b := &diff.ResourceBuilder{
+	log.Printf("[INFO] Deleting App: %s", d.Id())
-		Attrs: map[string]diff.AttrType{
+	err := client.AppDelete(d.Id())
-			"name":        diff.AttrTypeUpdate,
+	if err != nil {
-			"region":      diff.AttrTypeUpdate,
+		return fmt.Errorf("Error deleting App: %s", err)
-			"stack":       diff.AttrTypeCreate,
-			"config_vars": diff.AttrTypeUpdate,
-		},
-
-		ComputedAttrs: []string{
-			"name",
-			"region",
-			"stack",
-			"git_url",
-			"web_url",
-			"id",
-			"config_vars",
-		},
-
-		ComputedAttrsUpdate: []string{
-			"heroku_hostname",
-		},
 	}
 
-	return b.Diff(s, c)
+	d.SetId("")
-}
+	return nil
-
-func resource_heroku_app_update_state(
-	s *terraform.ResourceState,
-	app *application) (*terraform.ResourceState, error) {
-
-	s.Attributes["name"] = app.App.Name
-	s.Attributes["stack"] = app.App.Stack.Name
-	s.Attributes["region"] = app.App.Region.Name
-	s.Attributes["git_url"] = app.App.GitURL
-	s.Attributes["web_url"] = app.App.WebURL
-
-	// We know that the hostname on heroku will be the name+herokuapp.com
-	// You need this to do things like create DNS CNAME records
-	s.Attributes["heroku_hostname"] = fmt.Sprintf("%s.herokuapp.com", app.App.Name)
-
-	toFlatten := make(map[string]interface{})
-
-	if len(app.Vars) > 0 {
-		toFlatten["config_vars"] = []map[string]string{app.Vars}
-	}
-
-	for k, v := range flatmap.Flatten(toFlatten) {
-		s.Attributes[k] = v
-	}
-
-	return s, nil
 }
 
 func resource_heroku_app_retrieve(id string, client *heroku.Client) (*application, error) {
@@ -251,18 +215,6 @@ func resource_heroku_app_retrieve(id string, client *heroku.Client) (*applicatio
 	return &app, nil
 }
 
-func resource_heroku_app_validation() *config.Validator {
-	return &config.Validator{
-		Required: []string{},
-		Optional: []string{
-			"name",
-			"region",
-			"stack",
-			"config_vars.*",
-		},
-	}
-}
-
 func retrieve_config_vars(id string, client *heroku.Client) (map[string]string, error) {
 	vars, err := client.ConfigVarInfo(id)
 
@@ -273,21 +225,19 @@ func retrieve_config_vars(id string, client *heroku.Client) (map[string]string,
 	return vars, nil
 }
 
-// Updates the config vars for from an expanded (prior to assertion)
+// Updates the config vars for from an expanded configuration.
-// []map[string]string config
 func update_config_vars(id string, vs []interface{}, client *heroku.Client) error {
 	vars := make(map[string]*string)
 
-	for k, v := range vs[0].(map[string]interface{}) {
+	for _, v := range vs {
-		val := v.(string)
+		for k, v := range v.(map[string]interface{}) {
-		vars[k] = &val
+			val := v.(string)
+			vars[k] = &val
+		}
 	}
 
 	log.Printf("[INFO] Updating config vars: *%#v", vars)
-
+	if _, err := client.ConfigVarUpdate(id, vars); err != nil {
-	_, err := client.ConfigVarUpdate(id, vars)
-
-	if err != nil {
 		return fmt.Errorf("Error updating config vars: %s", err)
 	}
 

builtin/providers/heroku/resource_heroku_app_test.go

@@ -103,7 +103,7 @@ func TestAccHerokuApp_NukeVars(t *testing.T) {
 }
 
 func testAccCheckHerokuAppDestroy(s *terraform.State) error {
-	client := testAccProvider.client
+	client := testAccProvider.Meta().(*heroku.Client)
 
 	for _, rs := range s.Resources {
 		if rs.Type != "heroku_app" {
@@ -122,7 +122,7 @@ func testAccCheckHerokuAppDestroy(s *terraform.State) error {
 
 func testAccCheckHerokuAppAttributes(app *heroku.App) resource.TestCheckFunc {
 	return func(s *terraform.State) error {
-		client := testAccProvider.client
+		client := testAccProvider.Meta().(*heroku.Client)
 
 		if app.Region.Name != "us" {
 			return fmt.Errorf("Bad region: %s", app.Region.Name)
@@ -151,7 +151,7 @@ func testAccCheckHerokuAppAttributes(app *heroku.App) resource.TestCheckFunc {
 
 func testAccCheckHerokuAppAttributesUpdated(app *heroku.App) resource.TestCheckFunc {
 	return func(s *terraform.State) error {
-		client := testAccProvider.client
+		client := testAccProvider.Meta().(*heroku.Client)
 
 		if app.Name != "terraform-test-renamed" {
 			return fmt.Errorf("Bad name: %s", app.Name)
@@ -178,7 +178,7 @@ func testAccCheckHerokuAppAttributesUpdated(app *heroku.App) resource.TestCheckF
 
 func testAccCheckHerokuAppAttributesNoVars(app *heroku.App) resource.TestCheckFunc {
 	return func(s *terraform.State) error {
-		client := testAccProvider.client
+		client := testAccProvider.Meta().(*heroku.Client)
 
 		if app.Name != "terraform-test-app" {
 			return fmt.Errorf("Bad name: %s", app.Name)
@@ -209,7 +209,7 @@ func testAccCheckHerokuAppExists(n string, app *heroku.App) resource.TestCheckFu
 			return fmt.Errorf("No App Name is set")
 		}
 
-		client := testAccProvider.client
+		client := testAccProvider.Meta().(*heroku.Client)
 
 		foundApp, err := client.AppInfo(rs.ID)
 

builtin/providers/heroku/resource_heroku_domain.go

@@ -5,63 +5,64 @@ import (
 	"log"
 
 	"github.com/bgentry/heroku-go"
-	"github.com/hashicorp/terraform/helper/config"
+	"github.com/hashicorp/terraform/helper/schema"
-	"github.com/hashicorp/terraform/helper/diff"
-	"github.com/hashicorp/terraform/terraform"
 )
 
-func resource_heroku_domain_create(
+func resourceHerokuDomain() *schema.Resource {
-	s *terraform.ResourceState,
+	return &schema.Resource{
-	d *terraform.ResourceDiff,
+		Create: resourceHerokuDomainCreate,
-	meta interface{}) (*terraform.ResourceState, error) {
+		Read:   resourceHerokuDomainRead,
-	p := meta.(*ResourceProvider)
+		Delete: resourceHerokuDomainDelete,
-	client := p.client
 
-	// Merge the diff into the state so that we have all the attributes
+		Schema: map[string]*schema.Schema{
-	// properly.
+			"hostname": &schema.Schema{
-	rs := s.MergeDiff(d)
+				Type:     schema.TypeString,
+				Required: true,
+				ForceNew: true,
+			},
 
-	app := rs.Attributes["app"]
+			"app": &schema.Schema{
-	hostname := rs.Attributes["hostname"]
+				Type:     schema.TypeString,
+				Required: true,
+				ForceNew: true,
+			},
+
+			"cname": &schema.Schema{
+				Type:     schema.TypeString,
+				Computed: true,
+			},
+		},
+	}
+}
+
+func resourceHerokuDomainCreate(d *schema.ResourceData, meta interface{}) error {
+	client := meta.(*heroku.Client)
+
+	app := d.Get("app").(string)
+	hostname := d.Get("hostname").(string)
 
 	log.Printf("[DEBUG] Domain create configuration: %#v, %#v", app, hostname)
 
 	do, err := client.DomainCreate(app, hostname)
-
 	if err != nil {
-		return s, err
+		return err
 	}
 
-	rs.ID = do.Id
+	d.SetId(do.Id)
-	rs.Attributes["hostname"] = do.Hostname
+	d.Set("hostname", do.Hostname)
-	rs.Attributes["cname"] = fmt.Sprintf("%s.herokuapp.com", app)
+	d.Set("cname", fmt.Sprintf("%s.herokuapp.com", app))
 
-	log.Printf("[INFO] Domain ID: %s", rs.ID)
+	log.Printf("[INFO] Domain ID: %s", d.Id())
-
+	return nil
-	return rs, nil
 }
 
-func resource_heroku_domain_update(
+func resourceHerokuDomainDelete(d *schema.ResourceData, meta interface{}) error {
-	s *terraform.ResourceState,
+	client := meta.(*heroku.Client)
-	d *terraform.ResourceDiff,
-	meta interface{}) (*terraform.ResourceState, error) {
 
-	panic("Cannot update domain")
+	log.Printf("[INFO] Deleting Domain: %s", d.Id())
-
-	return nil, nil
-}
-
-func resource_heroku_domain_destroy(
-	s *terraform.ResourceState,
-	meta interface{}) error {
-	p := meta.(*ResourceProvider)
-	client := p.client
-
-	log.Printf("[INFO] Deleting Domain: %s", s.ID)
-
-	// Destroy the app
-	err := client.DomainDelete(s.Attributes["app"], s.ID)
 
+	// Destroy the domain
+	err := client.DomainDelete(d.Get("app").(string), d.Id())
 	if err != nil {
 		return fmt.Errorf("Error deleting domain: %s", err)
 	}
@@ -69,58 +70,17 @@ func resource_heroku_domain_destroy(
 	return nil
 }
 
-func resource_heroku_domain_refresh(
+func resourceHerokuDomainRead(d *schema.ResourceData, meta interface{}) error {
-	s *terraform.ResourceState,
+	client := meta.(*heroku.Client)
-	meta interface{}) (*terraform.ResourceState, error) {
-	p := meta.(*ResourceProvider)
-	client := p.client
 
-	domain, err := resource_heroku_domain_retrieve(s.Attributes["app"], s.ID, client)
+	app := d.Get("app").(string)
+	do, err := client.DomainInfo(app, d.Id())
 	if err != nil {
-		return nil, err
+		return fmt.Errorf("Error retrieving domain: %s", err)
 	}
 
-	s.Attributes["hostname"] = domain.Hostname
+	d.Set("hostname", do.Hostname)
-	s.Attributes["cname"] = fmt.Sprintf("%s.herokuapp.com", s.Attributes["app"])
+	d.Set("cname", fmt.Sprintf("%s.herokuapp.com", app))
 
-	return s, nil
+	return nil
-}
-
-func resource_heroku_domain_diff(
-	s *terraform.ResourceState,
-	c *terraform.ResourceConfig,
-	meta interface{}) (*terraform.ResourceDiff, error) {
-
-	b := &diff.ResourceBuilder{
-		Attrs: map[string]diff.AttrType{
-			"hostname": diff.AttrTypeCreate,
-			"app":      diff.AttrTypeCreate,
-		},
-
-		ComputedAttrs: []string{
-			"cname",
-		},
-	}
-
-	return b.Diff(s, c)
-}
-
-func resource_heroku_domain_retrieve(app string, id string, client *heroku.Client) (*heroku.Domain, error) {
-	domain, err := client.DomainInfo(app, id)
-
-	if err != nil {
-		return nil, fmt.Errorf("Error retrieving domain: %s", err)
-	}
-
-	return domain, nil
-}
-
-func resource_heroku_domain_validation() *config.Validator {
-	return &config.Validator{
-		Required: []string{
-			"hostname",
-			"app",
-		},
-		Optional: []string{},
-	}
 }

builtin/providers/heroku/resource_heroku_domain_test.go

@@ -35,7 +35,7 @@ func TestAccHerokuDomain_Basic(t *testing.T) {
 }
 
 func testAccCheckHerokuDomainDestroy(s *terraform.State) error {
-	client := testAccProvider.client
+	client := testAccProvider.Meta().(*heroku.Client)
 
 	for _, rs := range s.Resources {
 		if rs.Type != "heroku_domain" {
@@ -75,7 +75,7 @@ func testAccCheckHerokuDomainExists(n string, Domain *heroku.Domain) resource.Te
 			return fmt.Errorf("No Domain ID is set")
 		}
 
-		client := testAccProvider.client
+		client := testAccProvider.Meta().(*heroku.Client)
 
 		foundDomain, err := client.DomainInfo(rs.Attributes["app"], rs.ID)
 

builtin/providers/heroku/resource_heroku_drain.go

@@ -5,63 +5,64 @@ import (
 	"log"
 
 	"github.com/bgentry/heroku-go"
-	"github.com/hashicorp/terraform/helper/config"
+	"github.com/hashicorp/terraform/helper/schema"
-	"github.com/hashicorp/terraform/helper/diff"
-	"github.com/hashicorp/terraform/terraform"
 )
 
-func resource_heroku_drain_create(
+func resourceHerokuDrain() *schema.Resource {
-	s *terraform.ResourceState,
+	return &schema.Resource{
-	d *terraform.ResourceDiff,
+		Create: resourceHerokuDrainCreate,
-	meta interface{}) (*terraform.ResourceState, error) {
+		Read:   resourceHerokuDrainRead,
-	p := meta.(*ResourceProvider)
+		Delete: resourceHerokuDrainDelete,
-	client := p.client
 
-	// Merge the diff into the state so that we have all the attributes
+		Schema: map[string]*schema.Schema{
-	// properly.
+			"url": &schema.Schema{
-	rs := s.MergeDiff(d)
+				Type:     schema.TypeString,
+				Required: true,
+				ForceNew: true,
+			},
 
-	app := rs.Attributes["app"]
+			"app": &schema.Schema{
-	url := rs.Attributes["url"]
+				Type:     schema.TypeString,
+				Required: true,
+				ForceNew: true,
+			},
+
+			"token": &schema.Schema{
+				Type:     schema.TypeString,
+				Computed: true,
+			},
+		},
+	}
+}
+
+func resourceHerokuDrainCreate(d *schema.ResourceData, meta interface{}) error {
+	client := meta.(*heroku.Client)
+
+	app := d.Get("app").(string)
+	url := d.Get("url").(string)
 
 	log.Printf("[DEBUG] Drain create configuration: %#v, %#v", app, url)
 
 	dr, err := client.LogDrainCreate(app, url)
-
 	if err != nil {
-		return s, err
+		return err
 	}
 
-	rs.ID = dr.Id
+	d.SetId(dr.Id)
-	rs.Attributes["url"] = dr.URL
+	d.Set("url", dr.URL)
-	rs.Attributes["token"] = dr.Token
+	d.Set("token", dr.Token)
 
-	log.Printf("[INFO] Drain ID: %s", rs.ID)
+	log.Printf("[INFO] Drain ID: %s", d.Id())
-
+	return nil
-	return rs, nil
 }
 
-func resource_heroku_drain_update(
+func resourceHerokuDrainDelete(d *schema.ResourceData, meta interface{}) error {
-	s *terraform.ResourceState,
+	client := meta.(*heroku.Client)
-	d *terraform.ResourceDiff,
-	meta interface{}) (*terraform.ResourceState, error) {
 
-	panic("Cannot update drain")
+	log.Printf("[INFO] Deleting drain: %s", d.Id())
-
-	return nil, nil
-}
-
-func resource_heroku_drain_destroy(
-	s *terraform.ResourceState,
-	meta interface{}) error {
-	p := meta.(*ResourceProvider)
-	client := p.client
-
-	log.Printf("[INFO] Deleting drain: %s", s.ID)
-
-	// Destroy the app
-	err := client.LogDrainDelete(s.Attributes["app"], s.ID)
 
+	// Destroy the drain
+	err := client.LogDrainDelete(d.Get("app").(string), d.Id())
 	if err != nil {
 		return fmt.Errorf("Error deleting drain: %s", err)
 	}
@@ -69,58 +70,16 @@ func resource_heroku_drain_destroy(
 	return nil
 }
 
-func resource_heroku_drain_refresh(
+func resourceHerokuDrainRead(d *schema.ResourceData, meta interface{}) error {
-	s *terraform.ResourceState,
+	client := meta.(*heroku.Client)
-	meta interface{}) (*terraform.ResourceState, error) {
-	p := meta.(*ResourceProvider)
-	client := p.client
 
-	drain, err := resource_heroku_drain_retrieve(s.Attributes["app"], s.ID, client)
+	dr, err := client.LogDrainInfo(d.Get("app").(string), d.Id())
 	if err != nil {
-		return nil, err
+		return fmt.Errorf("Error retrieving drain: %s", err)
 	}
 
-	s.Attributes["url"] = drain.URL
+	d.Set("url", dr.URL)
-	s.Attributes["token"] = drain.Token
+	d.Set("token", dr.Token)
 
-	return s, nil
+	return nil
-}
-
-func resource_heroku_drain_diff(
-	s *terraform.ResourceState,
-	c *terraform.ResourceConfig,
-	meta interface{}) (*terraform.ResourceDiff, error) {
-
-	b := &diff.ResourceBuilder{
-		Attrs: map[string]diff.AttrType{
-			"url": diff.AttrTypeCreate,
-			"app": diff.AttrTypeCreate,
-		},
-
-		ComputedAttrs: []string{
-			"token",
-		},
-	}
-
-	return b.Diff(s, c)
-}
-
-func resource_heroku_drain_retrieve(app string, id string, client *heroku.Client) (*heroku.LogDrain, error) {
-	drain, err := client.LogDrainInfo(app, id)
-
-	if err != nil {
-		return nil, fmt.Errorf("Error retrieving drain: %s", err)
-	}
-
-	return drain, nil
-}
-
-func resource_heroku_drain_validation() *config.Validator {
-	return &config.Validator{
-		Required: []string{
-			"url",
-			"app",
-		},
-		Optional: []string{},
-	}
 }

builtin/providers/heroku/resource_heroku_drain_test.go

@@ -33,7 +33,7 @@ func TestAccHerokuDrain_Basic(t *testing.T) {
 }
 
 func testAccCheckHerokuDrainDestroy(s *terraform.State) error {
-	client := testAccProvider.client
+	client := testAccProvider.Meta().(*heroku.Client)
 
 	for _, rs := range s.Resources {
 		if rs.Type != "heroku_drain" {
@@ -77,7 +77,7 @@ func testAccCheckHerokuDrainExists(n string, Drain *heroku.LogDrain) resource.Te
 			return fmt.Errorf("No Drain ID is set")
 		}
 
-		client := testAccProvider.client
+		client := testAccProvider.Meta().(*heroku.Client)
 
 		foundDrain, err := client.LogDrainInfo(rs.Attributes["app"], rs.ID)
 

builtin/providers/heroku/resource_provider.go

@@ -1,68 +0,0 @@
-package heroku
-
-import (
-	"log"
-
-	"github.com/bgentry/heroku-go"
-	"github.com/hashicorp/terraform/helper/config"
-	"github.com/hashicorp/terraform/terraform"
-)
-
-type ResourceProvider struct {
-	Config Config
-
-	client *heroku.Client
-}
-
-func (p *ResourceProvider) Validate(c *terraform.ResourceConfig) ([]string, []error) {
-	v := &config.Validator{
-		Required: []string{
-			"email",
-			"api_key",
-		},
-	}
-
-	return v.Validate(c)
-}
-
-func (p *ResourceProvider) ValidateResource(
-	t string, c *terraform.ResourceConfig) ([]string, []error) {
-	return resourceMap.Validate(t, c)
-}
-
-func (p *ResourceProvider) Configure(c *terraform.ResourceConfig) error {
-	if _, err := config.Decode(&p.Config, c.Config); err != nil {
-		return err
-	}
-
-	log.Println("[INFO] Initializing Heroku client")
-	var err error
-	p.client, err = p.Config.Client()
-
-	if err != nil {
-		return err
-	}
-
-	return nil
-}
-
-func (p *ResourceProvider) Apply(
-	s *terraform.ResourceState,
-	d *terraform.ResourceDiff) (*terraform.ResourceState, error) {
-	return resourceMap.Apply(s, d, p)
-}
-
-func (p *ResourceProvider) Diff(
-	s *terraform.ResourceState,
-	c *terraform.ResourceConfig) (*terraform.ResourceDiff, error) {
-	return resourceMap.Diff(s, c, p)
-}
-
-func (p *ResourceProvider) Refresh(
-	s *terraform.ResourceState) (*terraform.ResourceState, error) {
-	return resourceMap.Refresh(s, p)
-}
-
-func (p *ResourceProvider) Resources() []terraform.ResourceType {
-	return resourceMap.Resources()
-}

builtin/providers/heroku/resources.go

@@ -1,49 +0,0 @@
-package heroku
-
-import (
-	"github.com/hashicorp/terraform/helper/resource"
-)
-
-// resourceMap is the mapping of resources we support to their basic
-// operations. This makes it easy to implement new resource types.
-var resourceMap *resource.Map
-
-func init() {
-	resourceMap = &resource.Map{
-		Mapping: map[string]resource.Resource{
-			"heroku_addon": resource.Resource{
-				ConfigValidator: resource_heroku_addon_validation(),
-				Create:          resource_heroku_addon_create,
-				Destroy:         resource_heroku_addon_destroy,
-				Diff:            resource_heroku_addon_diff,
-				Refresh:         resource_heroku_addon_refresh,
-				Update:          resource_heroku_addon_update,
-			},
-
-			"heroku_app": resource.Resource{
-				ConfigValidator: resource_heroku_app_validation(),
-				Create:          resource_heroku_app_create,
-				Destroy:         resource_heroku_app_destroy,
-				Diff:            resource_heroku_app_diff,
-				Refresh:         resource_heroku_app_refresh,
-				Update:          resource_heroku_app_update,
-			},
-
-			"heroku_domain": resource.Resource{
-				ConfigValidator: resource_heroku_domain_validation(),
-				Create:          resource_heroku_domain_create,
-				Destroy:         resource_heroku_domain_destroy,
-				Diff:            resource_heroku_domain_diff,
-				Refresh:         resource_heroku_domain_refresh,
-			},
-
-			"heroku_drain": resource.Resource{
-				ConfigValidator: resource_heroku_drain_validation(),
-				Create:          resource_heroku_drain_create,
-				Destroy:         resource_heroku_drain_destroy,
-				Diff:            resource_heroku_drain_diff,
-				Refresh:         resource_heroku_drain_refresh,
-			},
-		},
-	}
-}

helper/schema/README.md

@@ -0,0 +1,11 @@
+# Terraform Helper Lib: schema
+
+The `schema` package provides a high-level interface for writing resource
+providers for Terraform.
+
+If you're writing a resource provider, we recommend you use this package.
+
+The interface exposed by this package is much friendlier than trying to
+write to the Terraform API directly. The core Terraform API is low-level
+and built for maximum flexibility and control, whereas this library is built
+as a framework around that to more easily write common providers.

helper/schema/provider.go

@@ -0,0 +1,160 @@
+package schema
+
+import (
+	"errors"
+	"fmt"
+	"sort"
+
+	"github.com/hashicorp/terraform/terraform"
+)
+
+// Provider represents a Resource provider in Terraform, and properly
+// implements all of the ResourceProvider API.
+//
+// This is a friendlier API than the core Terraform ResourceProvider API,
+// and is recommended to be used over that.
+type Provider struct {
+	Schema       map[string]*Schema
+	ResourcesMap map[string]*Resource
+
+	ConfigureFunc ConfigureFunc
+
+	meta interface{}
+}
+
+// ConfigureFunc is the function used to configure a Provider.
+//
+// The interface{} value returned by this function is stored and passed into
+// the subsequent resources as the meta parameter.
+type ConfigureFunc func(*ResourceData) (interface{}, error)
+
+// InternalValidate should be called to validate the structure
+// of the provider.
+//
+// This should be called in a unit test for any provider to verify
+// before release that a provider is properly configured for use with
+// this library.
+func (p *Provider) InternalValidate() error {
+	if p == nil {
+		return errors.New("provider is nil")
+	}
+
+	if err := schemaMap(p.Schema).InternalValidate(); err != nil {
+		return err
+	}
+
+	for k, r := range p.ResourcesMap {
+		if err := r.InternalValidate(); err != nil {
+			return fmt.Errorf("%s: %s", k, err)
+		}
+	}
+
+	return nil
+}
+
+// Meta returns the metadata associated with this provider that was
+// returned by the Configure call. It will be nil until Configure is called.
+func (p *Provider) Meta() interface{} {
+	return p.meta
+}
+
+// Validate validates the provider configuration against the schema.
+func (p *Provider) Validate(c *terraform.ResourceConfig) ([]string, []error) {
+	return schemaMap(p.Schema).Validate(c)
+}
+
+// ValidateResource validates the resource configuration against the
+// proper schema.
+func (p *Provider) ValidateResource(
+	t string, c *terraform.ResourceConfig) ([]string, []error) {
+	r, ok := p.ResourcesMap[t]
+	if !ok {
+		return nil, []error{fmt.Errorf(
+			"Provider doesn't support resource: %s", t)}
+	}
+
+	return r.Validate(c)
+}
+
+// Configure implementation of terraform.ResourceProvider interface.
+func (p *Provider) Configure(c *terraform.ResourceConfig) error {
+	// No configuration
+	if p.ConfigureFunc == nil {
+		return nil
+	}
+
+	sm := schemaMap(p.Schema)
+
+	// Get a ResourceData for this configuration. To do this, we actually
+	// generate an intermediary "diff" although that is never exposed.
+	diff, err := sm.Diff(nil, c)
+	if err != nil {
+		return err
+	}
+
+	data, err := sm.Data(nil, diff)
+	if err != nil {
+		return err
+	}
+
+	meta, err := p.ConfigureFunc(data)
+	if err != nil {
+		return err
+	}
+
+	p.meta = meta
+	return nil
+}
+
+// Apply implementation of terraform.ResourceProvider interface.
+func (p *Provider) Apply(
+	s *terraform.ResourceState,
+	d *terraform.ResourceDiff) (*terraform.ResourceState, error) {
+	r, ok := p.ResourcesMap[s.Type]
+	if !ok {
+		return nil, fmt.Errorf("unknown resource type: %s", s.Type)
+	}
+
+	return r.Apply(s, d, p.meta)
+}
+
+// Diff implementation of terraform.ResourceProvider interface.
+func (p *Provider) Diff(
+	s *terraform.ResourceState,
+	c *terraform.ResourceConfig) (*terraform.ResourceDiff, error) {
+	r, ok := p.ResourcesMap[s.Type]
+	if !ok {
+		return nil, fmt.Errorf("unknown resource type: %s", s.Type)
+	}
+
+	return r.Diff(s, c)
+}
+
+// Refresh implementation of terraform.ResourceProvider interface.
+func (p *Provider) Refresh(
+	s *terraform.ResourceState) (*terraform.ResourceState, error) {
+	r, ok := p.ResourcesMap[s.Type]
+	if !ok {
+		return nil, fmt.Errorf("unknown resource type: %s", s.Type)
+	}
+
+	return r.Refresh(s, p.meta)
+}
+
+// Resources implementation of terraform.ResourceProvider interface.
+func (p *Provider) Resources() []terraform.ResourceType {
+	keys := make([]string, 0, len(p.ResourcesMap))
+	for k, _ := range p.ResourcesMap {
+		keys = append(keys, k)
+	}
+	sort.Strings(keys)
+
+	result := make([]terraform.ResourceType, 0, len(keys))
+	for _, k := range keys {
+		result = append(result, terraform.ResourceType{
+			Name: k,
+		})
+	}
+
+	return result
+}

helper/schema/provider_test.go

@@ -0,0 +1,157 @@
+package schema
+
+import (
+	"fmt"
+	"reflect"
+	"testing"
+
+	"github.com/hashicorp/terraform/config"
+	"github.com/hashicorp/terraform/terraform"
+)
+
+func TestProvider_impl(t *testing.T) {
+	var _ terraform.ResourceProvider = new(Provider)
+}
+
+func TestProviderConfigure(t *testing.T) {
+	cases := []struct {
+		P      *Provider
+		Config map[string]interface{}
+		Err    bool
+	}{
+		{
+			P:      &Provider{},
+			Config: nil,
+			Err:    false,
+		},
+
+		{
+			P: &Provider{
+				Schema: map[string]*Schema{
+					"foo": &Schema{
+						Type:     TypeInt,
+						Optional: true,
+					},
+				},
+
+				ConfigureFunc: func(d *ResourceData) (interface{}, error) {
+					if d.Get("foo").(int) == 42 {
+						return nil, nil
+					}
+
+					return nil, fmt.Errorf("nope")
+				},
+			},
+			Config: map[string]interface{}{
+				"foo": 42,
+			},
+			Err: false,
+		},
+
+		{
+			P: &Provider{
+				Schema: map[string]*Schema{
+					"foo": &Schema{
+						Type:     TypeInt,
+						Optional: true,
+					},
+				},
+
+				ConfigureFunc: func(d *ResourceData) (interface{}, error) {
+					if d.Get("foo").(int) == 42 {
+						return nil, nil
+					}
+
+					return nil, fmt.Errorf("nope")
+				},
+			},
+			Config: map[string]interface{}{
+				"foo": 52,
+			},
+			Err: true,
+		},
+	}
+
+	for i, tc := range cases {
+		c, err := config.NewRawConfig(tc.Config)
+		if err != nil {
+			t.Fatalf("err: %s", err)
+		}
+
+		err = tc.P.Configure(terraform.NewResourceConfig(c))
+		if (err != nil) != tc.Err {
+			t.Fatalf("%d: %s", i, err)
+		}
+	}
+}
+
+func TestProviderResources(t *testing.T) {
+	cases := []struct {
+		P      *Provider
+		Result []terraform.ResourceType
+	}{
+		{
+			P:      &Provider{},
+			Result: []terraform.ResourceType{},
+		},
+
+		{
+			P: &Provider{
+				ResourcesMap: map[string]*Resource{
+					"foo": nil,
+					"bar": nil,
+				},
+			},
+			Result: []terraform.ResourceType{
+				terraform.ResourceType{Name: "bar"},
+				terraform.ResourceType{Name: "foo"},
+			},
+		},
+	}
+
+	for i, tc := range cases {
+		actual := tc.P.Resources()
+		if !reflect.DeepEqual(actual, tc.Result) {
+			t.Fatalf("%d: %#v", i, actual)
+		}
+	}
+}
+
+func TestProviderValidateResource(t *testing.T) {
+	cases := []struct {
+		P      *Provider
+		Type   string
+		Config map[string]interface{}
+		Err    bool
+	}{
+		{
+			P:      &Provider{},
+			Type:   "foo",
+			Config: nil,
+			Err:    true,
+		},
+
+		{
+			P: &Provider{
+				ResourcesMap: map[string]*Resource{
+					"foo": &Resource{},
+				},
+			},
+			Type:   "foo",
+			Config: nil,
+			Err:    false,
+		},
+	}
+
+	for i, tc := range cases {
+		c, err := config.NewRawConfig(tc.Config)
+		if err != nil {
+			t.Fatalf("err: %s", err)
+		}
+
+		_, es := tc.P.ValidateResource(tc.Type, terraform.NewResourceConfig(c))
+		if (len(es) > 0) != tc.Err {
+			t.Fatalf("%d: %#v", i, es)
+		}
+	}
+}

helper/schema/resource.go

@@ -0,0 +1,135 @@
+package schema
+
+import (
+	"errors"
+	"fmt"
+
+	"github.com/hashicorp/terraform/terraform"
+)
+
+// The functions below are the CRUD function types for a Resource.
+//
+// The second parameter is the meta value sent to the resource when
+// different operations are called.
+type CreateFunc func(*ResourceData, interface{}) error
+type ReadFunc func(*ResourceData, interface{}) error
+type UpdateFunc func(*ResourceData, interface{}) error
+type DeleteFunc func(*ResourceData, interface{}) error
+
+// Resource represents a thing in Terraform that has a set of configurable
+// attributes and generally also has a lifecycle (create, read, update,
+// delete).
+//
+// The Resource schema is an abstraction that allows provider writers to
+// worry only about CRUD operations while off-loading validation, diff
+// generation, etc. to this higher level library.
+type Resource struct {
+	Schema map[string]*Schema
+
+	Create CreateFunc
+	Read   ReadFunc
+	Update UpdateFunc
+	Delete DeleteFunc
+}
+
+// Apply creates, updates, and/or deletes a resource.
+func (r *Resource) Apply(
+	s *terraform.ResourceState,
+	d *terraform.ResourceDiff,
+	meta interface{}) (*terraform.ResourceState, error) {
+	data, err := schemaMap(r.Schema).Data(s, d)
+	if err != nil {
+		return s, err
+	}
+
+	if s == nil {
+		// The Terraform API dictates that this should never happen, but
+		// it doesn't hurt to be safe in this case.
+		s = new(terraform.ResourceState)
+	}
+
+	if d.Destroy || d.RequiresNew() {
+		if s.ID != "" {
+			// Destroy the resource since it is created
+			if err := r.Delete(data, meta); err != nil {
+				return data.State(), err
+			}
+
+			// Reset the data to be empty
+			data, err = schemaMap(r.Schema).Data(nil, d)
+			if err != nil {
+				return nil, err
+			}
+		}
+
+		// If we're only destroying, and not creating, then return
+		// now since we're done!
+		if !d.RequiresNew() {
+			return nil, nil
+		}
+	}
+
+	err = nil
+	if s.ID == "" {
+		// We're creating, it is a new resource.
+		err = r.Create(data, meta)
+	} else {
+		if r.Update == nil {
+			return s, fmt.Errorf("%s doesn't support update", s.Type)
+		}
+
+		err = r.Update(data, meta)
+	}
+
+	// Always set the ID attribute if it is set. We also always collapse
+	// the state since even partial states need to be returned.
+	state := data.State()
+	if state.ID != "" {
+		if state.Attributes == nil {
+			state.Attributes = make(map[string]string)
+		}
+		state.Attributes["id"] = state.ID
+	}
+
+	return state, err
+}
+
+// Diff returns a diff of this resource and is API compatible with the
+// ResourceProvider interface.
+func (r *Resource) Diff(
+	s *terraform.ResourceState,
+	c *terraform.ResourceConfig) (*terraform.ResourceDiff, error) {
+	return schemaMap(r.Schema).Diff(s, c)
+}
+
+// Validate validates the resource configuration against the schema.
+func (r *Resource) Validate(c *terraform.ResourceConfig) ([]string, []error) {
+	return schemaMap(r.Schema).Validate(c)
+}
+
+// Refresh refreshes the state of the resource.
+func (r *Resource) Refresh(
+	s *terraform.ResourceState,
+	meta interface{}) (*terraform.ResourceState, error) {
+	data, err := schemaMap(r.Schema).Data(s, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	err = r.Read(data, meta)
+	return data.State(), err
+}
+
+// InternalValidate should be called to validate the structure
+// of the resource.
+//
+// This should be called in a unit test for any resource to verify
+// before release that a resource is properly configured for use with
+// this library.
+func (r *Resource) InternalValidate() error {
+	if r == nil {
+		return errors.New("resource is nil")
+	}
+
+	return schemaMap(r.Schema).InternalValidate()
+}

helper/schema/resource_data.go

@@ -0,0 +1,629 @@
+package schema
+
+import (
+	"fmt"
+	"reflect"
+	"strconv"
+	"strings"
+	"sync"
+
+	"github.com/hashicorp/terraform/terraform"
+	"github.com/mitchellh/mapstructure"
+)
+
+// getSource represents the level we want to get for a value (internally).
+// Any source less than or equal to the level will be loaded (whichever
+// has a value first).
+type getSource byte
+
+const (
+	getSourceState getSource = iota
+	getSourceDiff
+	getSourceSet
+)
+
+// ResourceData is used to query and set the attributes of a resource.
+type ResourceData struct {
+	schema map[string]*Schema
+	state  *terraform.ResourceState
+	diff   *terraform.ResourceDiff
+
+	setMap   map[string]string
+	newState *terraform.ResourceState
+	once     sync.Once
+}
+
+// Get returns the data for the given key, or nil if the key doesn't exist.
+//
+// The type of the data returned will be according to the schema specified.
+// Primitives will be their respective types in Go, lists will always be
+// []interface{}, and sub-resources will be map[string]interface{}.
+func (d *ResourceData) Get(key string) interface{} {
+	var parts []string
+	if key != "" {
+		parts = strings.Split(key, ".")
+	}
+
+	return d.getObject("", parts, d.schema, getSourceSet)
+}
+
+// GetChange returns the old and new value for a given key.
+//
+// If there is no change, then old and new will simply be the same.
+func (d *ResourceData) GetChange(key string) (interface{}, interface{}) {
+	var parts []string
+	if key != "" {
+		parts = strings.Split(key, ".")
+	}
+
+	o := d.getObject("", parts, d.schema, getSourceState)
+	n := d.getObject("", parts, d.schema, getSourceDiff)
+	return o, n
+}
+
+// HasChange returns whether or not the given key has been changed.
+func (d *ResourceData) HasChange(key string) bool {
+	o, n := d.GetChange(key)
+	return !reflect.DeepEqual(o, n)
+}
+
+// Set sets the value for the given key.
+//
+// If the key is invalid or the value is not a correct type, an error
+// will be returned.
+func (d *ResourceData) Set(key string, value interface{}) error {
+	if d.setMap == nil {
+		d.setMap = make(map[string]string)
+	}
+
+	parts := strings.Split(key, ".")
+	return d.setObject("", parts, d.schema, value)
+}
+
+// Id returns the ID of the resource.
+func (d *ResourceData) Id() string {
+	var result string
+
+	if d.state != nil {
+		result = d.state.ID
+	}
+
+	if d.newState != nil {
+		result = d.newState.ID
+	}
+
+	return result
+}
+
+// Dependencies returns the dependencies in this state.
+func (d *ResourceData) Dependencies() []terraform.ResourceDependency {
+	if d.newState != nil {
+		return d.newState.Dependencies
+	}
+
+	if d.state != nil {
+		return d.state.Dependencies
+	}
+
+	return nil
+}
+
+// SetId sets the ID of the resource. If the value is blank, then the
+// resource is destroyed.
+func (d *ResourceData) SetId(v string) {
+	d.once.Do(d.init)
+	d.newState.ID = v
+}
+
+// SetDependencies sets the dependencies of a resource.
+func (d *ResourceData) SetDependencies(ds []terraform.ResourceDependency) {
+	d.once.Do(d.init)
+	d.newState.Dependencies = ds
+}
+
+// State returns the new ResourceState after the diff and any Set
+// calls.
+func (d *ResourceData) State() *terraform.ResourceState {
+	var result terraform.ResourceState
+	result.ID = d.Id()
+	result.Attributes = d.stateObject("", d.schema)
+	result.Dependencies = d.Dependencies()
+
+	return &result
+}
+
+func (d *ResourceData) init() {
+	var copyState terraform.ResourceState
+	if d.state != nil {
+		copyState = *d.state
+	}
+
+	d.newState = &copyState
+}
+
+func (d *ResourceData) get(
+	k string,
+	parts []string,
+	schema *Schema,
+	source getSource) interface{} {
+	switch schema.Type {
+	case TypeList:
+		return d.getList(k, parts, schema, source)
+	case TypeMap:
+		return d.getMap(k, parts, schema, source)
+	default:
+		return d.getPrimitive(k, parts, schema, source)
+	}
+}
+
+func (d *ResourceData) getMap(
+	k string,
+	parts []string,
+	schema *Schema,
+	source getSource) interface{} {
+	elemSchema := &Schema{Type: TypeString}
+
+	result := make(map[string]interface{})
+	prefix := k + "."
+
+	if d.state != nil && source >= getSourceState {
+		for k, _ := range d.state.Attributes {
+			if !strings.HasPrefix(k, prefix) {
+				continue
+			}
+
+			single := k[len(prefix):]
+			result[single] = d.getPrimitive(k, nil, elemSchema, source)
+		}
+	}
+
+	if d.diff != nil && source >= getSourceDiff {
+		for k, v := range d.diff.Attributes {
+			if !strings.HasPrefix(k, prefix) {
+				continue
+			}
+
+			single := k[len(prefix):]
+
+			if v.NewRemoved {
+				delete(result, single)
+			} else {
+				result[single] = d.getPrimitive(k, nil, elemSchema, source)
+			}
+		}
+	}
+
+	if d.setMap != nil && source >= getSourceSet {
+		cleared := false
+		for k, _ := range d.setMap {
+			if !strings.HasPrefix(k, prefix) {
+				continue
+			}
+			if !cleared {
+				// We clear the results if they are in the set map
+				result = make(map[string]interface{})
+				cleared = true
+			}
+
+			single := k[len(prefix):]
+			result[single] = d.getPrimitive(k, nil, elemSchema, source)
+		}
+	}
+
+	return result
+}
+
+func (d *ResourceData) getObject(
+	k string,
+	parts []string,
+	schema map[string]*Schema,
+	source getSource) interface{} {
+	if len(parts) > 0 {
+		// We're requesting a specific key in an object
+		key := parts[0]
+		parts = parts[1:]
+		s, ok := schema[key]
+		if !ok {
+			return nil
+		}
+
+		if k != "" {
+			// If we're not at the root, then we need to append
+			// the key to get the full key path.
+			key = fmt.Sprintf("%s.%s", k, key)
+		}
+
+		return d.get(key, parts, s, source)
+	}
+
+	// Get the entire object
+	result := make(map[string]interface{})
+	for field, _ := range schema {
+		result[field] = d.getObject(k, []string{field}, schema, source)
+	}
+
+	return result
+}
+
+func (d *ResourceData) getList(
+	k string,
+	parts []string,
+	schema *Schema,
+	source getSource) interface{} {
+	if len(parts) > 0 {
+		// We still have parts left over meaning we're accessing an
+		// element of this list.
+		idx := parts[0]
+		parts = parts[1:]
+
+		// Special case if we're accessing the count of the list
+		if idx == "#" {
+			schema := &Schema{Type: TypeInt}
+			result := d.get(k+".#", parts, schema, source)
+			if result == nil {
+				result = 0
+			}
+
+			return result
+		}
+
+		key := fmt.Sprintf("%s.%s", k, idx)
+		switch t := schema.Elem.(type) {
+		case *Resource:
+			return d.getObject(key, parts, t.Schema, source)
+		case *Schema:
+			return d.get(key, parts, t, source)
+		}
+	}
+
+	// Get the entire list.
+	result := make(
+		[]interface{},
+		d.getList(k, []string{"#"}, schema, source).(int))
+	for i, _ := range result {
+		is := strconv.FormatInt(int64(i), 10)
+		result[i] = d.getList(k, []string{is}, schema, source)
+	}
+
+	return result
+}
+
+func (d *ResourceData) getPrimitive(
+	k string,
+	parts []string,
+	schema *Schema,
+	source getSource) interface{} {
+	var result string
+	var resultSet bool
+	if d.state != nil && source >= getSourceState {
+		result, resultSet = d.state.Attributes[k]
+	}
+
+	if d.diff != nil && source >= getSourceDiff {
+		attrD, ok := d.diff.Attributes[k]
+		if ok && !attrD.NewComputed {
+			result = attrD.New
+			resultSet = true
+		}
+	}
+
+	if d.setMap != nil && source >= getSourceSet {
+		if v, ok := d.setMap[k]; ok {
+			result = v
+			resultSet = true
+		}
+	}
+
+	if !resultSet {
+		return nil
+	}
+
+	switch schema.Type {
+	case TypeString:
+		// Use the value as-is. We just put this case here to be explicit.
+		return result
+	case TypeInt:
+		if result == "" {
+			return 0
+		}
+
+		v, err := strconv.ParseInt(result, 0, 0)
+		if err != nil {
+			panic(err)
+		}
+
+		return int(v)
+	default:
+		panic(fmt.Sprintf("Unknown type: %s", schema.Type))
+	}
+}
+
+func (d *ResourceData) set(
+	k string,
+	parts []string,
+	schema *Schema,
+	value interface{}) error {
+	switch schema.Type {
+	case TypeList:
+		return d.setList(k, parts, schema, value)
+	case TypeMap:
+		return d.setMapValue(k, parts, schema, value)
+	default:
+		return d.setPrimitive(k, schema, value)
+	}
+}
+
+func (d *ResourceData) setList(
+	k string,
+	parts []string,
+	schema *Schema,
+	value interface{}) error {
+	if len(parts) > 0 {
+		// We're setting a specific element
+		idx := parts[0]
+		parts = parts[1:]
+
+		// Special case if we're accessing the count of the list
+		if idx == "#" {
+			return fmt.Errorf("%s: can't set count of list", k)
+		}
+
+		key := fmt.Sprintf("%s.%s", k, idx)
+		switch t := schema.Elem.(type) {
+		case *Resource:
+			return d.setObject(key, parts, t.Schema, value)
+		case *Schema:
+			return d.set(key, parts, t, value)
+		}
+	}
+
+	var vs []interface{}
+	if err := mapstructure.Decode(value, &vs); err != nil {
+		return fmt.Errorf("%s: %s", k, err)
+	}
+
+	// Set the entire list.
+	var err error
+	for i, elem := range vs {
+		is := strconv.FormatInt(int64(i), 10)
+		err = d.setList(k, []string{is}, schema, elem)
+		if err != nil {
+			break
+		}
+	}
+	if err != nil {
+		for i, _ := range vs {
+			is := strconv.FormatInt(int64(i), 10)
+			d.setList(k, []string{is}, schema, nil)
+		}
+
+		return err
+	}
+
+	d.setMap[k+".#"] = strconv.FormatInt(int64(len(vs)), 10)
+	return nil
+}
+
+func (d *ResourceData) setMapValue(
+	k string,
+	parts []string,
+	schema *Schema,
+	value interface{}) error {
+	elemSchema := &Schema{Type: TypeString}
+	if len(parts) > 0 {
+		return fmt.Errorf("%s: full map must be set, no a single element", k)
+	}
+
+	// Delete any prior map set
+	/*
+		v := d.getMap(k, nil, schema, getSourceSet)
+		for subKey, _ := range v.(map[string]interface{}) {
+			delete(d.setMap, fmt.Sprintf("%s.%s", k, subKey))
+		}
+	*/
+
+	v := reflect.ValueOf(value)
+	if v.Kind() != reflect.Map {
+		return fmt.Errorf("%s: must be a map", k)
+	}
+	if v.Type().Key().Kind() != reflect.String {
+		return fmt.Errorf("%s: keys must strings", k)
+	}
+	vs := make(map[string]interface{})
+	for _, mk := range v.MapKeys() {
+		mv := v.MapIndex(mk)
+		vs[mk.String()] = mv.Interface()
+	}
+
+	for subKey, v := range vs {
+		err := d.set(fmt.Sprintf("%s.%s", k, subKey), nil, elemSchema, v)
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func (d *ResourceData) setObject(
+	k string,
+	parts []string,
+	schema map[string]*Schema,
+	value interface{}) error {
+	if len(parts) > 0 {
+		// We're setting a specific key in an object
+		key := parts[0]
+		parts = parts[1:]
+
+		s, ok := schema[key]
+		if !ok {
+			return fmt.Errorf("%s (internal): unknown key to set: %s", k, key)
+		}
+
+		if k != "" {
+			// If we're not at the root, then we need to append
+			// the key to get the full key path.
+			key = fmt.Sprintf("%s.%s", k, key)
+		}
+
+		return d.set(key, parts, s, value)
+	}
+
+	// Set the entire object. First decode into a proper structure
+	var v map[string]interface{}
+	if err := mapstructure.Decode(value, &v); err != nil {
+		return fmt.Errorf("%s: %s", k, err)
+	}
+
+	// Set each element in turn
+	var err error
+	for k1, v1 := range v {
+		err = d.setObject(k, []string{k1}, schema, v1)
+		if err != nil {
+			break
+		}
+	}
+	if err != nil {
+		for k1, _ := range v {
+			d.setObject(k, []string{k1}, schema, nil)
+		}
+	}
+
+	return err
+}
+
+func (d *ResourceData) setPrimitive(
+	k string,
+	schema *Schema,
+	v interface{}) error {
+	if v == nil {
+		delete(d.setMap, k)
+		return nil
+	}
+
+	var set string
+	switch schema.Type {
+	case TypeString:
+		if err := mapstructure.Decode(v, &set); err != nil {
+			return fmt.Errorf("%s: %s", k, err)
+		}
+	case TypeInt:
+		var n int
+		if err := mapstructure.Decode(v, &n); err != nil {
+			return fmt.Errorf("%s: %s", k, err)
+		}
+
+		set = strconv.FormatInt(int64(n), 10)
+	default:
+		return fmt.Errorf("Unknown type: %s", schema.Type)
+	}
+
+	d.setMap[k] = set
+	return nil
+}
+
+func (d *ResourceData) stateList(
+	prefix string,
+	schema *Schema) map[string]string {
+	countRaw := d.get(prefix, []string{"#"}, schema, getSourceSet)
+	if countRaw == nil {
+		return nil
+	}
+	count := countRaw.(int)
+
+	result := make(map[string]string)
+	if count > 0 {
+		result[prefix+".#"] = strconv.FormatInt(int64(count), 10)
+	}
+	for i := 0; i < count; i++ {
+		key := fmt.Sprintf("%s.%d", prefix, i)
+
+		var m map[string]string
+		switch t := schema.Elem.(type) {
+		case *Resource:
+			m = d.stateObject(key, t.Schema)
+		case *Schema:
+			m = d.stateSingle(key, t)
+		}
+
+		for k, v := range m {
+			result[k] = v
+		}
+	}
+
+	return result
+}
+
+func (d *ResourceData) stateMap(
+	prefix string,
+	schema *Schema) map[string]string {
+	v := d.getMap(prefix, nil, schema, getSourceSet)
+	if v == nil {
+		return nil
+	}
+
+	elemSchema := &Schema{Type: TypeString}
+	result := make(map[string]string)
+	for mk, _ := range v.(map[string]interface{}) {
+		mp := fmt.Sprintf("%s.%s", prefix, mk)
+		for k, v := range d.stateSingle(mp, elemSchema) {
+			result[k] = v
+		}
+	}
+
+	return result
+}
+
+func (d *ResourceData) stateObject(
+	prefix string,
+	schema map[string]*Schema) map[string]string {
+	result := make(map[string]string)
+	for k, v := range schema {
+		key := k
+		if prefix != "" {
+			key = prefix + "." + key
+		}
+
+		for k1, v1 := range d.stateSingle(key, v) {
+			result[k1] = v1
+		}
+	}
+
+	return result
+}
+
+func (d *ResourceData) statePrimitive(
+	prefix string,
+	schema *Schema) map[string]string {
+	v := d.getPrimitive(prefix, nil, schema, getSourceSet)
+	if v == nil {
+		return nil
+	}
+
+	var vs string
+	switch schema.Type {
+	case TypeString:
+		vs = v.(string)
+	case TypeInt:
+		vs = strconv.FormatInt(int64(v.(int)), 10)
+	default:
+		panic(fmt.Sprintf("Unknown type: %s", schema.Type))
+	}
+
+	return map[string]string{
+		prefix: vs,
+	}
+}
+
+func (d *ResourceData) stateSingle(
+	prefix string,
+	schema *Schema) map[string]string {
+	switch schema.Type {
+	case TypeList:
+		return d.stateList(prefix, schema)
+	case TypeMap:
+		return d.stateMap(prefix, schema)
+	default:
+		return d.statePrimitive(prefix, schema)
+	}
+}

helper/schema/resource_test.go

@@ -0,0 +1,306 @@
+package schema
+
+import (
+	"fmt"
+	"reflect"
+	"testing"
+
+	"github.com/hashicorp/terraform/terraform"
+)
+
+func TestResourceApply_create(t *testing.T) {
+	r := &Resource{
+		Schema: map[string]*Schema{
+			"foo": &Schema{
+				Type:     TypeInt,
+				Optional: true,
+			},
+		},
+	}
+
+	called := false
+	r.Create = func(d *ResourceData, m interface{}) error {
+		called = true
+		d.SetId("foo")
+		return nil
+	}
+
+	var s *terraform.ResourceState = nil
+
+	d := &terraform.ResourceDiff{
+		Attributes: map[string]*terraform.ResourceAttrDiff{
+			"foo": &terraform.ResourceAttrDiff{
+				New: "42",
+			},
+		},
+	}
+
+	actual, err := r.Apply(s, d, nil)
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	if !called {
+		t.Fatal("not called")
+	}
+
+	expected := &terraform.ResourceState{
+		ID: "foo",
+		Attributes: map[string]string{
+			"id":  "foo",
+			"foo": "42",
+		},
+	}
+
+	if !reflect.DeepEqual(actual, expected) {
+		t.Fatalf("bad: %#v", actual)
+	}
+}
+
+func TestResourceApply_destroy(t *testing.T) {
+	r := &Resource{
+		Schema: map[string]*Schema{
+			"foo": &Schema{
+				Type:     TypeInt,
+				Optional: true,
+			},
+		},
+	}
+
+	called := false
+	r.Delete = func(d *ResourceData, m interface{}) error {
+		called = true
+		return nil
+	}
+
+	s := &terraform.ResourceState{
+		ID: "bar",
+	}
+
+	d := &terraform.ResourceDiff{
+		Destroy: true,
+	}
+
+	actual, err := r.Apply(s, d, nil)
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	if !called {
+		t.Fatal("delete not called")
+	}
+
+	if actual != nil {
+		t.Fatalf("bad: %#v", actual)
+	}
+}
+
+func TestResourceApply_destroyPartial(t *testing.T) {
+	r := &Resource{
+		Schema: map[string]*Schema{
+			"foo": &Schema{
+				Type:     TypeInt,
+				Optional: true,
+			},
+		},
+	}
+
+	r.Delete = func(d *ResourceData, m interface{}) error {
+		d.Set("foo", 42)
+		return fmt.Errorf("some error")
+	}
+
+	s := &terraform.ResourceState{
+		ID: "bar",
+		Attributes: map[string]string{
+			"foo": "12",
+		},
+	}
+
+	d := &terraform.ResourceDiff{
+		Destroy: true,
+	}
+
+	actual, err := r.Apply(s, d, nil)
+	if err == nil {
+		t.Fatal("should error")
+	}
+
+	expected := &terraform.ResourceState{
+		ID: "bar",
+		Attributes: map[string]string{
+			"foo": "42",
+		},
+	}
+
+	if !reflect.DeepEqual(actual, expected) {
+		t.Fatalf("bad: %#v", actual)
+	}
+}
+
+func TestResourceApply_update(t *testing.T) {
+	r := &Resource{
+		Schema: map[string]*Schema{
+			"foo": &Schema{
+				Type:     TypeInt,
+				Optional: true,
+			},
+		},
+	}
+
+	r.Update = func(d *ResourceData, m interface{}) error {
+		d.Set("foo", 42)
+		return nil
+	}
+
+	s := &terraform.ResourceState{
+		ID: "foo",
+		Attributes: map[string]string{
+			"foo": "12",
+		},
+	}
+
+	d := &terraform.ResourceDiff{
+		Attributes: map[string]*terraform.ResourceAttrDiff{
+			"foo": &terraform.ResourceAttrDiff{
+				New: "13",
+			},
+		},
+	}
+
+	actual, err := r.Apply(s, d, nil)
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	expected := &terraform.ResourceState{
+		ID: "foo",
+		Attributes: map[string]string{
+			"id":  "foo",
+			"foo": "42",
+		},
+	}
+
+	if !reflect.DeepEqual(actual, expected) {
+		t.Fatalf("bad: %#v", actual)
+	}
+}
+
+func TestResourceApply_updateNoCallback(t *testing.T) {
+	r := &Resource{
+		Schema: map[string]*Schema{
+			"foo": &Schema{
+				Type:     TypeInt,
+				Optional: true,
+			},
+		},
+	}
+
+	r.Update = nil
+
+	s := &terraform.ResourceState{
+		ID: "foo",
+		Attributes: map[string]string{
+			"foo": "12",
+		},
+	}
+
+	d := &terraform.ResourceDiff{
+		Attributes: map[string]*terraform.ResourceAttrDiff{
+			"foo": &terraform.ResourceAttrDiff{
+				New: "13",
+			},
+		},
+	}
+
+	actual, err := r.Apply(s, d, nil)
+	if err == nil {
+		t.Fatal("should error")
+	}
+
+	expected := &terraform.ResourceState{
+		ID: "foo",
+		Attributes: map[string]string{
+			"foo": "12",
+		},
+	}
+
+	if !reflect.DeepEqual(actual, expected) {
+		t.Fatalf("bad: %#v", actual)
+	}
+}
+
+func TestResourceInternalValidate(t *testing.T) {
+	cases := []struct {
+		In  *Resource
+		Err bool
+	}{
+		{
+			nil,
+			true,
+		},
+
+		// No optional and no required
+		{
+			&Resource{
+				Schema: map[string]*Schema{
+					"foo": &Schema{
+						Type:     TypeInt,
+						Optional: true,
+						Required: true,
+					},
+				},
+			},
+			true,
+		},
+	}
+
+	for i, tc := range cases {
+		err := tc.In.InternalValidate()
+		if (err != nil) != tc.Err {
+			t.Fatalf("%d: bad: %s", i, err)
+		}
+	}
+}
+
+func TestResourceRefresh(t *testing.T) {
+	r := &Resource{
+		Schema: map[string]*Schema{
+			"foo": &Schema{
+				Type:     TypeInt,
+				Optional: true,
+			},
+		},
+	}
+
+	r.Read = func(d *ResourceData, m interface{}) error {
+		if m != 42 {
+			return fmt.Errorf("meta not passed")
+		}
+
+		return d.Set("foo", d.Get("foo").(int)+1)
+	}
+
+	s := &terraform.ResourceState{
+		ID: "bar",
+		Attributes: map[string]string{
+			"foo": "12",
+		},
+	}
+
+	expected := &terraform.ResourceState{
+		ID: "bar",
+		Attributes: map[string]string{
+			"foo": "13",
+		},
+	}
+
+	actual, err := r.Refresh(s, 42)
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	if !reflect.DeepEqual(actual, expected) {
+		t.Fatalf("bad: %#v", actual)
+	}
+}

helper/schema/schema.go

@@ -0,0 +1,564 @@
+package schema
+
+import (
+	"fmt"
+	"reflect"
+	"strconv"
+	"strings"
+
+	"github.com/hashicorp/terraform/terraform"
+	"github.com/mitchellh/mapstructure"
+)
+
+// ValueType is an enum of the type that can be represented by a schema.
+type ValueType int
+
+const (
+	TypeInvalid ValueType = iota
+	TypeBool
+	TypeInt
+	TypeString
+	TypeList
+	TypeMap
+)
+
+// Schema is used to describe the structure of a value.
+type Schema struct {
+	// Type is the type of the value and must be one of the ValueType values.
+	Type ValueType
+
+	// If one of these is set, then this item can come from the configuration.
+	// Both cannot be set. If Optional is set, the value is optional. If
+	// Required is set, the value is required.
+	Optional bool
+	Required bool
+
+	// The fields below relate to diffs.
+	//
+	// If Computed is true, then the result of this value is computed
+	// (unless specified by config) on creation.
+	//
+	// If ForceNew is true, then a change in this resource necessitates
+	// the creation of a new resource.
+	Computed bool
+	ForceNew bool
+
+	// The following fields are only set for a TypeList Type.
+	//
+	// Elem must be either a *Schema or a *Resource only if the Type is
+	// TypeList, and represents what the element type is. If it is *Schema,
+	// the element type is just a simple value. If it is *Resource, the
+	// element type is a complex structure, potentially with its own lifecycle.
+	Elem interface{}
+
+	// ComputedWhen is a set of queries on the configuration. Whenever any
+	// of these things is changed, it will require a recompute (this requires
+	// that Computed is set to true).
+	ComputedWhen []string
+}
+
+func (s *Schema) finalizeDiff(
+	d *terraform.ResourceAttrDiff) *terraform.ResourceAttrDiff {
+	if d == nil {
+		return d
+	}
+
+	if s.Computed {
+		if d.Old != "" && d.New == "" {
+			// This is a computed value with an old value set already,
+			// just let it go.
+			return nil
+		}
+
+		if d.New == "" {
+			// Computed attribute without a new value set
+			d.NewComputed = true
+		}
+	}
+
+	if s.ForceNew {
+		// Force new, set it to true in the diff
+		d.RequiresNew = true
+	}
+
+	return d
+}
+
+// schemaMap is a wrapper that adds nice functions on top of schemas.
+type schemaMap map[string]*Schema
+
+// Data returns a ResourceData for the given schema, state, and diff.
+//
+// The diff is optional.
+func (m schemaMap) Data(
+	s *terraform.ResourceState,
+	d *terraform.ResourceDiff) (*ResourceData, error) {
+	return &ResourceData{
+		schema: m,
+		state:  s,
+		diff:   d,
+	}, nil
+}
+
+// Diff returns the diff for a resource given the schema map,
+// state, and configuration.
+func (m schemaMap) Diff(
+	s *terraform.ResourceState,
+	c *terraform.ResourceConfig) (*terraform.ResourceDiff, error) {
+	result := new(terraform.ResourceDiff)
+	result.Attributes = make(map[string]*terraform.ResourceAttrDiff)
+
+	for k, schema := range m {
+		err := m.diff(k, schema, result, s, c)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	// Remove any nil diffs just to keep things clean
+	for k, v := range result.Attributes {
+		if v == nil {
+			delete(result.Attributes, k)
+		}
+	}
+
+	// Go through and detect all of the ComputedWhens now that we've
+	// finished the diff.
+	// TODO
+
+	if result.Empty() {
+		// If we don't have any diff elements, just return nil
+		return nil, nil
+	}
+
+	return result, nil
+}
+
+// Validate validates the configuration against this schema mapping.
+func (m schemaMap) Validate(c *terraform.ResourceConfig) ([]string, []error) {
+	return m.validateObject("", m, c)
+}
+
+// InternalValidate validates the format of this schema. This should be called
+// from a unit test (and not in user-path code) to verify that a schema
+// is properly built.
+func (m schemaMap) InternalValidate() error {
+	for k, v := range m {
+		if v.Type == TypeInvalid {
+			return fmt.Errorf("%s: Type must be specified", k)
+		}
+
+		if v.Optional && v.Required {
+			return fmt.Errorf("%s: Optional or Required must be set, not both", k)
+		}
+
+		if v.Required && v.Computed {
+			return fmt.Errorf("%s: Cannot be both Required and Computed", k)
+		}
+
+		if len(v.ComputedWhen) > 0 && !v.Computed {
+			return fmt.Errorf("%s: ComputedWhen can only be set with Computed", k)
+		}
+
+		if v.Type == TypeList {
+			if v.Elem == nil {
+				return fmt.Errorf("%s: Elem must be set for lists", k)
+			}
+
+			switch t := v.Elem.(type) {
+			case *Resource:
+				if err := t.InternalValidate(); err != nil {
+					return err
+				}
+			case *Schema:
+				bad := t.Computed || t.Optional || t.Required
+				if bad {
+					return fmt.Errorf(
+						"%s: Elem must have only Type set", k)
+				}
+			}
+		}
+	}
+
+	return nil
+}
+
+func (m schemaMap) diff(
+	k string,
+	schema *Schema,
+	diff *terraform.ResourceDiff,
+	s *terraform.ResourceState,
+	c *terraform.ResourceConfig) error {
+	var err error
+	switch schema.Type {
+	case TypeBool:
+		fallthrough
+	case TypeInt:
+		fallthrough
+	case TypeString:
+		err = m.diffString(k, schema, diff, s, c)
+	case TypeList:
+		err = m.diffList(k, schema, diff, s, c)
+	case TypeMap:
+		err = m.diffMap(k, schema, diff, s, c)
+	default:
+		err = fmt.Errorf("%s: unknown type %s", k, schema.Type)
+	}
+
+	return err
+}
+
+func (m schemaMap) diffList(
+	k string,
+	schema *Schema,
+	diff *terraform.ResourceDiff,
+	s *terraform.ResourceState,
+	c *terraform.ResourceConfig) error {
+	var vs []interface{}
+
+	v, ok := c.Get(k)
+	if ok {
+		// We have to use reflection to build the []interface{} list
+		rawV := reflect.ValueOf(v)
+		if rawV.Kind() != reflect.Slice {
+			return fmt.Errorf("%s: must be a list", k)
+		}
+		vs = make([]interface{}, rawV.Len())
+		for i, _ := range vs {
+			vs[i] = rawV.Index(i).Interface()
+		}
+	}
+
+	// If this field is required, then it must also be non-empty
+	if len(vs) == 0 && schema.Required {
+		return fmt.Errorf("%s: required field is not set", k)
+	}
+
+	// Get the counts
+	var oldLen, newLen int
+	if s != nil {
+		if v, ok := s.Attributes[k+".#"]; ok {
+			old64, err := strconv.ParseInt(v, 0, 0)
+			if err != nil {
+				return err
+			}
+			oldLen = int(old64)
+		}
+	}
+	newLen = len(vs)
+
+	// If the counts are not the same, then record that diff
+	changed := oldLen != newLen
+	computed := oldLen == 0 && newLen == 0 && schema.Computed
+	if changed || computed {
+		countSchema := &Schema{
+			Type:     TypeInt,
+			Computed: schema.Computed,
+			ForceNew: schema.ForceNew,
+		}
+
+		oldStr := ""
+		newStr := ""
+		if !computed {
+			oldStr = strconv.FormatInt(int64(oldLen), 10)
+			newStr = strconv.FormatInt(int64(newLen), 10)
+		}
+
+		diff.Attributes[k+".#"] = countSchema.finalizeDiff(&terraform.ResourceAttrDiff{
+			Old: oldStr,
+			New: newStr,
+		})
+	}
+
+	// Figure out the maximum
+	maxLen := oldLen
+	if newLen > maxLen {
+		maxLen = newLen
+	}
+
+	switch t := schema.Elem.(type) {
+	case *Schema:
+		// Copy the schema so that we can set Computed/ForceNew from
+		// the parent schema (the TypeList).
+		t2 := *t
+		t2.ForceNew = schema.ForceNew
+
+		// This is just a primitive element, so go through each and
+		// just diff each.
+		for i := 0; i < maxLen; i++ {
+			subK := fmt.Sprintf("%s.%d", k, i)
+			err := m.diff(subK, &t2, diff, s, c)
+			if err != nil {
+				return err
+			}
+		}
+	case *Resource:
+		// This is a complex resource
+		for i := 0; i < maxLen; i++ {
+			for k2, schema := range t.Schema {
+				subK := fmt.Sprintf("%s.%d.%s", k, i, k2)
+				err := m.diff(subK, schema, diff, s, c)
+				if err != nil {
+					return err
+				}
+			}
+		}
+	default:
+		return fmt.Errorf("%s: unknown element type (internal)", k)
+	}
+
+	return nil
+}
+
+func (m schemaMap) diffMap(
+	k string,
+	schema *Schema,
+	diff *terraform.ResourceDiff,
+	s *terraform.ResourceState,
+	c *terraform.ResourceConfig) error {
+	//elemSchema := &Schema{Type: TypeString}
+	prefix := k + "."
+
+	// First get all the values from the state
+	stateMap := make(map[string]string)
+	if s != nil {
+		for sk, sv := range s.Attributes {
+			if !strings.HasPrefix(sk, prefix) {
+				continue
+			}
+
+			stateMap[sk[len(prefix):]] = sv
+		}
+	}
+
+	// Then get all the values from the configuration
+	configMap := make(map[string]string)
+	if c != nil {
+		if raw, ok := c.Get(k); ok {
+			for k, v := range raw.(map[string]interface{}) {
+				configMap[k] = v.(string)
+			}
+		}
+	}
+
+	// Now we compare, preferring values from the config map
+	for k, v := range configMap {
+		old := stateMap[k]
+		delete(stateMap, k)
+
+		if old == v {
+			continue
+		}
+
+		diff.Attributes[prefix+k] = schema.finalizeDiff(&terraform.ResourceAttrDiff{
+			Old: old,
+			New: v,
+		})
+	}
+	for k, v := range stateMap {
+		diff.Attributes[prefix+k] = schema.finalizeDiff(&terraform.ResourceAttrDiff{
+			Old:        v,
+			NewRemoved: true,
+		})
+	}
+
+	return nil
+}
+
+func (m schemaMap) diffString(
+	k string,
+	schema *Schema,
+	diff *terraform.ResourceDiff,
+	s *terraform.ResourceState,
+	c *terraform.ResourceConfig) error {
+	var old, n string
+	if s != nil {
+		old = s.Attributes[k]
+	}
+
+	v, ok := c.Get(k)
+	if !ok {
+		// We don't have a value, if it is required then it is an error
+		if schema.Required {
+			return fmt.Errorf("%s: required field not set", k)
+		}
+
+		// If we don't have an old value, just return
+		if old == "" && !schema.Computed {
+			return nil
+		}
+	} else {
+		if err := mapstructure.WeakDecode(v, &n); err != nil {
+			return fmt.Errorf("%s: %s", k, err)
+		}
+
+		if old == n {
+			// They're the same value
+			return nil
+		}
+	}
+
+	diff.Attributes[k] = schema.finalizeDiff(&terraform.ResourceAttrDiff{
+		Old: old,
+		New: n,
+	})
+
+	return nil
+}
+
+func (m schemaMap) diffPrimitive(
+	k string,
+	nraw interface{},
+	schema *Schema,
+	diff *terraform.ResourceDiff,
+	s *terraform.ResourceState) error {
+	var old, n string
+	if s != nil {
+		old = s.Attributes[k]
+	}
+
+	if err := mapstructure.WeakDecode(nraw, &n); err != nil {
+		return fmt.Errorf("%s: %s", k, err)
+	}
+
+	if old == n {
+		// They're the same value
+		return nil
+	}
+
+	diff.Attributes[k] = schema.finalizeDiff(&terraform.ResourceAttrDiff{
+		Old: old,
+		New: n,
+	})
+
+	return nil
+}
+
+func (m schemaMap) validate(
+	k string,
+	schema *Schema,
+	c *terraform.ResourceConfig) ([]string, []error) {
+	raw, ok := c.Get(k)
+	if !ok {
+		if schema.Required {
+			return nil, []error{fmt.Errorf(
+				"%s: required field is not set", k)}
+		}
+
+		return nil, nil
+	}
+
+	if !schema.Required && !schema.Optional {
+		// This is a computed-only field
+		return nil, []error{fmt.Errorf(
+			"%s: this field cannot be set", k)}
+	}
+
+	return m.validatePrimitive(k, raw, schema, c)
+}
+
+func (m schemaMap) validateList(
+	k string,
+	raw interface{},
+	schema *Schema,
+	c *terraform.ResourceConfig) ([]string, []error) {
+	// We use reflection to verify the slice because you can't
+	// case to []interface{} unless the slice is exactly that type.
+	rawV := reflect.ValueOf(raw)
+	if rawV.Kind() != reflect.Slice {
+		return nil, []error{fmt.Errorf(
+			"%s: should be a list", k)}
+	}
+
+	// Now build the []interface{}
+	raws := make([]interface{}, rawV.Len())
+	for i, _ := range raws {
+		raws[i] = rawV.Index(i).Interface()
+	}
+
+	var ws []string
+	var es []error
+	for i, raw := range raws {
+		key := fmt.Sprintf("%s.%d", k, i)
+
+		var ws2 []string
+		var es2 []error
+		switch t := schema.Elem.(type) {
+		case *Resource:
+			// This is a sub-resource
+			ws2, es2 = m.validateObject(key, t.Schema, c)
+		case *Schema:
+			// This is some sort of primitive
+			ws2, es2 = m.validatePrimitive(key, raw, t, c)
+		}
+
+		if len(ws2) > 0 {
+			ws = append(ws, ws2...)
+		}
+		if len(es2) > 0 {
+			es = append(es, es2...)
+		}
+	}
+
+	return ws, es
+}
+
+func (m schemaMap) validateObject(
+	k string,
+	schema map[string]*Schema,
+	c *terraform.ResourceConfig) ([]string, []error) {
+	var ws []string
+	var es []error
+	for subK, s := range schema {
+		key := subK
+		if k != "" {
+			key = fmt.Sprintf("%s.%s", k, subK)
+		}
+
+		ws2, es2 := m.validate(key, s, c)
+		if len(ws2) > 0 {
+			ws = append(ws, ws2...)
+		}
+		if len(es2) > 0 {
+			es = append(es, es2...)
+		}
+	}
+
+	// Detect any extra/unknown keys and report those as errors.
+	prefix := k + "."
+	for configK, _ := range c.Raw {
+		if k != "" {
+			if !strings.HasPrefix(configK, prefix) {
+				continue
+			}
+
+			configK = configK[len(prefix):]
+		}
+
+		if _, ok := schema[configK]; !ok {
+			es = append(es, fmt.Errorf(
+				"%s: invalid or unknown key: %s", k, configK))
+		}
+	}
+
+	return ws, es
+}
+
+func (m schemaMap) validatePrimitive(
+	k string,
+	raw interface{},
+	schema *Schema,
+	c *terraform.ResourceConfig) ([]string, []error) {
+	switch schema.Type {
+	case TypeList:
+		return m.validateList(k, raw, schema, c)
+	case TypeInt:
+		// Verify that we can parse this as an int
+		var n int
+		if err := mapstructure.WeakDecode(raw, &n); err != nil {
+			return nil, []error{err}
+		}
+	}
+
+	return nil, nil
+}

terraform/context.go

@@ -75,9 +75,11 @@ func NewContext(opts *ContextOpts) *Context {
 
 	// Calculate all the default variables
 	defaultVars := make(map[string]string)
-	for _, v := range opts.Config.Variables {
+	if opts.Config != nil {
-		for k, val := range v.DefaultsMap() {
+		for _, v := range opts.Config.Variables {
-			defaultVars[k] = val
+			for k, val := range v.DefaultsMap() {
+				defaultVars[k] = val
+			}
 		}
 	}
 

terraform/resource.go

@@ -89,34 +89,14 @@ func (c *ResourceConfig) CheckSet(keys []string) []error {
 // The second return value is true if the get was successful. Get will
 // not succeed if the value is being computed.
 func (c *ResourceConfig) Get(k string) (interface{}, bool) {
-	parts := strings.Split(k, ".")
+	// First try to get it from c.Config since that has interpolated values
-
+	result, ok := c.get(k, c.Config)
-	var current interface{} = c.Raw
+	if ok {
-	for _, part := range parts {
+		return result, ok
-		if current == nil {
-			return nil, false
-		}
-
-		cv := reflect.ValueOf(current)
-		switch cv.Kind() {
-		case reflect.Map:
-			v := cv.MapIndex(reflect.ValueOf(part))
-			if !v.IsValid() {
-				return nil, false
-			}
-			current = v.Interface()
-		case reflect.Slice:
-			i, err := strconv.ParseInt(part, 0, 0)
-			if err != nil {
-				return nil, false
-			}
-			current = cv.Index(int(i)).Interface()
-		default:
-			panic(fmt.Sprintf("Unknown kind: %s", cv.Kind()))
-		}
 	}
 
-	return current, true
+	// Otherwise, just get it from the raw config
+	return c.get(k, c.Raw)
 }
 
 // IsSet checks if the key in the configuration is set. A key is set if
@@ -143,6 +123,42 @@ func (c *ResourceConfig) IsSet(k string) bool {
 	return false
 }
 
+func (c *ResourceConfig) get(
+	k string, raw map[string]interface{}) (interface{}, bool) {
+	parts := strings.Split(k, ".")
+
+	var current interface{} = raw
+	for _, part := range parts {
+		if current == nil {
+			return nil, false
+		}
+
+		cv := reflect.ValueOf(current)
+		switch cv.Kind() {
+		case reflect.Map:
+			v := cv.MapIndex(reflect.ValueOf(part))
+			if !v.IsValid() {
+				return nil, false
+			}
+			current = v.Interface()
+		case reflect.Slice:
+			if part == "#" {
+				current = cv.Len()
+			} else {
+				i, err := strconv.ParseInt(part, 0, 0)
+				if err != nil {
+					return nil, false
+				}
+				current = cv.Index(int(i)).Interface()
+			}
+		default:
+			panic(fmt.Sprintf("Unknown kind: %s", cv.Kind()))
+		}
+	}
+
+	return current, true
+}
+
 func (c *ResourceConfig) interpolate(ctx *Context) error {
 	if c == nil {
 		return nil

terraform/resource_test.go

@@ -3,6 +3,8 @@ package terraform
 import (
 	"reflect"
 	"testing"
+
+	"github.com/hashicorp/terraform/config"
 )
 
 func TestResource_Vars(t *testing.T) {
@@ -29,3 +31,49 @@ func TestResource_Vars(t *testing.T) {
 		t.Fatalf("bad: %#v", actual)
 	}
 }
+
+func TestResourceConfigGet(t *testing.T) {
+	cases := []struct {
+		Config map[string]interface{}
+		Vars   map[string]string
+		Key    string
+		Value  interface{}
+	}{
+		{
+			Config: map[string]interface{}{
+				"foo": "${var.foo}",
+			},
+			Key:   "foo",
+			Value: "${var.foo}",
+		},
+
+		{
+			Config: map[string]interface{}{
+				"foo": "${var.foo}",
+			},
+			Vars:  map[string]string{"foo": "bar"},
+			Key:   "foo",
+			Value: "bar",
+		},
+	}
+
+	for i, tc := range cases {
+		rawC, err := config.NewRawConfig(tc.Config)
+		if err != nil {
+			t.Fatalf("err: %s", err)
+		}
+		rc := NewResourceConfig(rawC)
+
+		if tc.Vars != nil {
+			ctx := NewContext(&ContextOpts{Variables: tc.Vars})
+			if err := rc.interpolate(ctx); err != nil {
+				t.Fatalf("err: %s", err)
+			}
+		}
+
+		v, _ := rc.Get(tc.Key)
+		if !reflect.DeepEqual(v, tc.Value) {
+			t.Fatalf("%d bad: %#v", i, v)
+		}
+	}
+}