provider/test: allow assigning a label to each instance

When testing the behavior of multiple provider instances (either aliases
or child module overrides) it's convenient to be able to label the
individual instances to determine which one is actually being used for
the purpose of making test assertions.

builtin/providers/test/data_source_label.go

@@ -0,0 +1,25 @@
+package test
+
+import (
+	"github.com/hashicorp/terraform/helper/schema"
+)
+
+func providerLabelDataSource() *schema.Resource {
+	return &schema.Resource{
+		Read: providerLabelDataSourceRead,
+
+		Schema: map[string]*schema.Schema{
+			"label": {
+				Type:     schema.TypeString,
+				Computed: true,
+			},
+		},
+	}
+}
+
+func providerLabelDataSourceRead(d *schema.ResourceData, meta interface{}) error {
+	label := meta.(string)
+	d.SetId(label)
+	d.Set("label", label)
+	return nil
+}

builtin/providers/test/data_source_label_test.go

@@ -0,0 +1,45 @@
+package test
+
+import (
+	"errors"
+	"fmt"
+	"strings"
+	"testing"
+
+	"github.com/hashicorp/terraform/helper/resource"
+	"github.com/hashicorp/terraform/terraform"
+)
+
+func TestProviderLabelDataSource(t *testing.T) {
+	resource.UnitTest(t, resource.TestCase{
+		Providers: testAccProviders,
+		CheckDestroy: func(s *terraform.State) error {
+			return nil
+		},
+		Steps: []resource.TestStep{
+			{
+				Config: strings.TrimSpace(`
+provider "test" {
+  label = "foo"
+}
+
+data "test_provider_label" "test" {
+}
+				`),
+				Check: func(s *terraform.State) error {
+					res, hasRes := s.RootModule().Resources["data.test_provider_label.test"]
+					if !hasRes {
+						return errors.New("No test_provider_label in state")
+					}
+					if got, want := res.Primary.ID, "foo"; got != want {
+						return fmt.Errorf("wrong id %q; want %q", got, want)
+					}
+					if got, want := res.Primary.Attributes["label"], "foo"; got != want {
+						return fmt.Errorf("wrong id %q; want %q", got, want)
+					}
+					return nil
+				},
+			},
+		},
+	})
+}

builtin/providers/test/provider.go

@@ -7,17 +7,27 @@ import (
 
 func Provider() terraform.ResourceProvider {
 	return &schema.Provider{
+		Schema: map[string]*schema.Schema{
+			// Optional attribute to label a particular instance for a test
+			// that has multiple instances of this provider, so that they
+			// can be distinguished using the test_provider_label data source.
+			"label": {
+				Type:     schema.TypeString,
+				Optional: true,
+			},
+		},
 		ResourcesMap: map[string]*schema.Resource{
 			"test_resource":         testResource(),
 			"test_resource_gh12183": testResourceGH12183(),
 		},
 		DataSourcesMap: map[string]*schema.Resource{
-			"test_data_source": testDataSource(),
+			"test_data_source":    testDataSource(),
+			"test_provider_label": providerLabelDataSource(),
 		},
 		ConfigureFunc: providerConfigure,
 	}
 }
 
 func providerConfigure(d *schema.ResourceData) (interface{}, error) {
-	return nil, nil
+	return d.Get("label"), nil
 }