helper/schema: support top-level TypeMap

helper/schema/resource_data.go

@@ -372,9 +372,22 @@ func (d *ResourceData) getMap(
 
 	if d.config != nil && source == getSourceConfig {
 		// For config, we always set the result to exactly what was requested
-		if m, ok := d.config.Get(k); ok {
+		if mraw, ok := d.config.Get(k); ok {
-			result = m.(map[string]interface{})
+			switch m := mraw.(type) {
+			case []interface{}:
+				for _, innerRaw := range m {
+					for k, v := range innerRaw.(map[string]interface{}) {
+						result[k] = v
+					}
+				}
+
 				resultSet = true
+			case map[string]interface{}:
+				result = m
+				resultSet = true
+			default:
+				panic(fmt.Sprintf("unknown type: %#v", mraw))
+			}
 		} else {
 			result = nil
 		}

helper/schema/schema_test.go

@@ -835,6 +835,35 @@ func TestSchemaMap_Diff(t *testing.T) {
 		 * Maps
 		 */
 
+		{
+			Schema: map[string]*Schema{
+				"config_vars": &Schema{
+					Type: TypeMap,
+				},
+			},
+
+			State: nil,
+
+			Config: map[string]interface{}{
+				"config_vars": []interface{}{
+					map[string]interface{}{
+						"bar": "baz",
+					},
+				},
+			},
+
+			Diff: &terraform.InstanceDiff{
+				Attributes: map[string]*terraform.ResourceAttrDiff{
+					"config_vars.bar": &terraform.ResourceAttrDiff{
+						Old: "",
+						New: "baz",
+					},
+				},
+			},
+
+			Err: false,
+		},
+
 		{
 			Schema: map[string]*Schema{
 				"config_vars": &Schema{