terraform: add ResourceProviderFactoryFixed

terraform/resource_provider.go

@@ -69,6 +69,14 @@ type ResourceType struct {
 // of a resource provider.
 type ResourceProviderFactory func() (ResourceProvider, error)
 
+// ResourceProviderFactoryFixed is a helper that creates a
+// ResourceProviderFactory that just returns some fixed provider.
+func ResourceProviderFactoryFixed(p ResourceProvider) ResourceProviderFactory {
+	return func() (ResourceProvider, error) {
+		return p, nil
+	}
+}
+
 func ProviderSatisfies(p ResourceProvider, n string) bool {
 	for _, rt := range p.Resources() {
 		if rt.Name == n {

terraform/resource_provider_test.go

@@ -175,3 +175,15 @@ func TestResourceConfig_IsSet_nil(t *testing.T) {
 		t.Fatal("bad")
 	}
 }
+
+func TestResourceProviderFactoryFixed(t *testing.T) {
+	p := new(MockResourceProvider)
+	var f ResourceProviderFactory = ResourceProviderFactoryFixed(p)
+	actual, err := f()
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	if actual != p {
+		t.Fatal("should be identical")
+	}
+}