helper/schema: can specify Importer on Resource, InternalValidate

helper/schema/resource.go

@@ -78,6 +78,13 @@ type Resource struct {
 	Update UpdateFunc
 	Delete DeleteFunc
 	Exists ExistsFunc
+
+	// Importer is the ResourceImporter implementation for this resource.
+	// If this is nil, then this resource does not support importing. If
+	// this is non-nil, then it supports importing and ResourceImporter
+	// must be validated. The validity of ResourceImporter is verified
+	// by InternalValidate on Resource.
+	Importer *ResourceImporter
 }
 
 // See Resource documentation.
@@ -260,6 +267,13 @@ func (r *Resource) InternalValidate(topSchemaMap schemaMap) error {
 		}
 
 		tsm = schemaMap(r.Schema)
+
+		// If we have an importer, we need to verify the importer.
+		if r.Importer != nil {
+			if err := r.Importer.InternalValidate(); err != nil {
+				return err
+			}
+		}
 	}
 
 	return schemaMap(r.Schema).InternalValidate(tsm)

helper/schema/resource_importer.go

@@ -27,4 +27,18 @@ type ResourceImporter struct {
 // that was given to the function. In other cases (such as AWS security groups),
 // an import may fan out to multiple resources and this will have to return
 // multiple.
+//
+// To create the ResourceData structures for other resource types (if
+// you have to), instantiate your resource and call the Data function.
 type StateFunc func(*ResourceData, interface{}) ([]*ResourceData, error)
+
+// InternalValidate should be called to validate the structure of this
+// importer. This should be called in a unit test.
+//
+// Resource.InternalValidate() will automatically call this, so this doesn't
+// need to be called manually. Further, Resource.InternalValidate() is
+// automatically called by Provider.InternalValidate(), so you only need
+// to internal validate the provider.
+func (r *ResourceImporter) InternalValidate() error {
+	return nil
+}