terraform: diff hooks

command/plan.go

@@ -62,6 +62,7 @@ func (c *PlanCommand) Run(args []string) int {
 		return 1
 	}
 
+	c.TFConfig.Hooks = append(c.TFConfig.Hooks, &UiHook{Ui: c.Ui})
 	tf, err := terraform.New(c.TFConfig)
 	if err != nil {
 		c.Ui.Error(fmt.Sprintf("Error initializing Terraform: %s", err))

main.go

@@ -7,9 +7,7 @@ import (
 	"log"
 	"os"
 
-	"github.com/hashicorp/terraform/command"
 	"github.com/hashicorp/terraform/plugin"
-	"github.com/hashicorp/terraform/terraform"
 	"github.com/mitchellh/cli"
 	"github.com/mitchellh/panicwrap"
 	"github.com/mitchellh/prefixedio"
@@ -86,7 +84,6 @@ func wrappedMain() int {
 	defer plugin.CleanupClients()
 
 	// Initialize the TFConfig settings for the commands...
-	TFConfig.Hooks = []terraform.Hook{&command.UiHook{Ui: Ui}}
 	TFConfig.Providers = config.ProviderFactories()
 
 	// Get the command line args. We shortcut "--version" and "-v" to

terraform/hook.go

@@ -21,10 +21,14 @@ const (
 // NilHook into your struct, which implements all of the interface but does
 // nothing. Then, override only the functions you want to implement.
 type Hook interface {
-	// PreRefresh is called before a resource is refreshed.
-	PreRefresh(string, *ResourceState) (HookAction, error)
+	// PreDiff and PostDiff are called before and after a single resource
+	// resource is diffed.
+	PreDiff(string, *ResourceState) (HookAction, error)
+	PostDiff(string, *ResourceDiff) (HookAction, error)
 
-	// PostRefresh is called after a resource is refreshed.
+	// PreRefresh and PostRefresh are called before and after a single
+	// resource state is refreshed, respectively.
+	PreRefresh(string, *ResourceState) (HookAction, error)
 	PostRefresh(string, *ResourceState) (HookAction, error)
 }
 
@@ -33,6 +37,14 @@ type Hook interface {
 // and only implement the functions you are interested in.
 type NilHook struct{}
 
+func (*NilHook) PreDiff(string, *ResourceState) (HookAction, error) {
+	return HookActionContinue, nil
+}
+
+func (*NilHook) PostDiff(string, *ResourceDiff) (HookAction, error) {
+	return HookActionContinue, nil
+}
+
 func (*NilHook) PreRefresh(string, *ResourceState) (HookAction, error) {
 	return HookActionContinue, nil
 }

terraform/hook_mock.go

@@ -3,6 +3,18 @@ package terraform
 // MockHook is an implementation of Hook that can be used for tests.
 // It records all of its function calls.
 type MockHook struct {
+	PreDiffCalled bool
+	PreDiffId     string
+	PreDiffState  *ResourceState
+	PreDiffReturn HookAction
+	PreDiffError  error
+
+	PostDiffCalled bool
+	PostDiffId     string
+	PostDiffDiff   *ResourceDiff
+	PostDiffReturn HookAction
+	PostDiffError  error
+
 	PostRefreshCalled bool
 	PostRefreshId     string
 	PostRefreshState  *ResourceState
@@ -16,6 +28,20 @@ type MockHook struct {
 	PreRefreshError  error
 }
 
+func (h *MockHook) PreDiff(n string, s *ResourceState) (HookAction, error) {
+	h.PreDiffCalled = true
+	h.PreDiffId = n
+	h.PreDiffState = s
+	return h.PreDiffReturn, h.PreDiffError
+}
+
+func (h *MockHook) PostDiff(n string, d *ResourceDiff) (HookAction, error) {
+	h.PostDiffCalled = true
+	h.PostDiffId = n
+	h.PostDiffDiff = d
+	return h.PostDiffReturn, h.PostDiffError
+}
+
 func (h *MockHook) PreRefresh(n string, s *ResourceState) (HookAction, error) {
 	h.PreRefreshCalled = true
 	h.PreRefreshId = n

terraform/terraform.go

@@ -243,6 +243,11 @@ func (t *Terraform) planWalkFn(
 	cb := func(r *Resource) (map[string]string, error) {
 		var diff *ResourceDiff
 
+		for _, h := range t.hooks {
+			// TODO: return value
+			h.PreDiff(r.Id, r.State)
+		}
+
 		if r.Config == nil {
 			log.Printf("[DEBUG] %s: Orphan, marking for destroy", r.Id)
 
@@ -265,6 +270,11 @@ func (t *Terraform) planWalkFn(
 		}
 		l.Unlock()
 
+		for _, h := range t.hooks {
+			// TODO: return value
+			h.PostDiff(r.Id, diff)
+		}
+
 		// Determine the new state and update variables
 		vars := make(map[string]string)
 		if !diff.Empty() {
@@ -311,7 +321,7 @@ func (t *Terraform) genericWalkFn(
 			}
 
 			for k, p := range m.Providers {
-				log.Printf("Configuring provider: %s", k)
+				log.Printf("[INFO] Configuring provider: %s", k)
 				err := p.Configure(rc)
 				if err != nil {
 					return err
@@ -345,7 +355,7 @@ func (t *Terraform) genericWalkFn(
 		}
 
 		// Call the callack
-		log.Printf("Walking: %s", rn.Resource.Id)
+		log.Printf("[INFO] Walking: %s", rn.Resource.Id)
 		newVars, err := cb(rn.Resource)
 		if err != nil {
 			return err

terraform/terraform_test.go

@@ -161,6 +161,24 @@ func TestTerraformPlan_computed(t *testing.T) {
 	}
 }
 
+func TestTerraformPlan_hook(t *testing.T) {
+	c := testConfig(t, "plan-good")
+	h := new(MockHook)
+	tf := testTerraform2(t, &Config{
+		Hooks: []Hook{h},
+	})
+
+	if _, err := tf.Plan(c, nil, nil); err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	if !h.PreDiffCalled {
+		t.Fatal("should be called")
+	}
+	if !h.PostDiffCalled {
+		t.Fatal("should be called")
+	}
+}
+
 func TestTerraformPlan_orphan(t *testing.T) {
 	c := testConfig(t, "plan-orphan")
 	tf := testTerraform2(t, nil)
@@ -462,11 +480,13 @@ func testProviderMock(p ResourceProvider) *MockResourceProvider {
 
 func testTerraform2(t *testing.T, c *Config) *Terraform {
 	if c == nil {
-		c = &Config{
-			Providers: map[string]ResourceProviderFactory{
+		c = new(Config)
+	}
+
+	if c.Providers == nil {
+		c.Providers = map[string]ResourceProviderFactory{
 			"aws": testProviderFunc("aws", []string{"aws_instance"}),
 			"do":  testProviderFunc("do", []string{"do_droplet"}),
-			},
 		}
 	}