Updated the provider to make testing a little easier

Also makes the provider more inline with the others following the TF
0.2 approach.

builtin/providers/mailgun/config.go

@@ -2,25 +2,18 @@ package mailgun
 
 import (
 	"log"
-	"os"
 
 	"github.com/pearkes/mailgun"
 )
 
 type Config struct {
-	APIKey string `mapstructure:"api_key"`
+	APIKey string
 }
 
 // Client() returns a new client for accessing mailgun.
 //
 func (c *Config) Client() (*mailgun.Client, error) {
 
-	// If we have env vars set (like in the acc) tests,
-	// we need to override the values passed in here.
-	if v := os.Getenv("MAILGUN_API_KEY"); v != "" {
-		c.APIKey = v
-	}
-
 	// We don't set a domain right away
 	client, err := mailgun.NewClient(c.APIKey)
 

builtin/providers/mailgun/provider.go

@@ -2,10 +2,10 @@ package mailgun
 
 import (
 	"log"
+	"os"
 
 	"github.com/hashicorp/terraform/helper/schema"
 	"github.com/hashicorp/terraform/terraform"
-	"github.com/mitchellh/mapstructure"
 )
 
 // Provider returns a terraform.ResourceProvider.
@@ -15,6 +15,7 @@ func Provider() terraform.ResourceProvider {
 			"api_key": &schema.Schema{
 				Type:        schema.TypeString,
 				Required:    true,
+				DefaultFunc: envDefaultFunc("MAILGUN_API_KEY"),
 			},
 		},
 
@@ -26,14 +27,21 @@ func Provider() terraform.ResourceProvider {
 	}
 }
 
+func envDefaultFunc(k string) schema.SchemaDefaultFunc {
+	return func() (interface{}, error) {
+		if v := os.Getenv(k); v != "" {
+			return v, nil
+		}
+
+		return nil, nil
+	}
+}
+
 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
+	config := Config{
+		APIKey: d.Get("api_key").(string),
 	}
 
 	log.Println("[INFO] Initializing Mailgun client")
-
 	return config.Client()
 }

builtin/providers/mailgun/provider_test.go

@@ -4,10 +4,8 @@ import (
 	"os"
 	"testing"
 
-	"github.com/hashicorp/terraform/config"
 	"github.com/hashicorp/terraform/helper/schema"
 	"github.com/hashicorp/terraform/terraform"
-	"github.com/pearkes/mailgun"
 )
 
 var testAccProviders map[string]terraform.ResourceProvider
@@ -30,36 +28,6 @@ func TestProvider_impl(t *testing.T) {
 	var _ terraform.ResourceProvider = Provider()
 }
 
-func TestProviderConfigure(t *testing.T) {
-	var expectedKey string
-
-	if v := os.Getenv("MAILGUN_API_KEY"); v != "" {
-		expectedKey = v
-	} else {
-		expectedKey = "foo"
-	}
-
-	raw := map[string]interface{}{
-		"api_key": expectedKey,
-	}
-
-	rawConfig, err := config.NewRawConfig(raw)
-	if err != nil {
-		t.Fatalf("err: %s", err)
-	}
-
-	rp := Provider().(*schema.Provider)
-	err = rp.Configure(terraform.NewResourceConfig(rawConfig))
-	if err != nil {
-		t.Fatalf("err: %s", err)
-	}
-
-	config := rp.Meta().(*mailgun.Client)
-	if config.ApiKey != expectedKey {
-		t.Fatalf("bad: %#v", config)
-	}
-}
-
 func testAccPreCheck(t *testing.T) {
 	if v := os.Getenv("MAILGUN_API_KEY"); v == "" {
 		t.Fatal("MAILGUN_API_KEY must be set for acceptance tests")