helper/resource: RetryError for quitting quickly

helper/resource/wait.go

@@ -18,14 +18,29 @@ func Retry(timeout time.Duration, f RetryFunc) error {
 		MinTimeout: 500 * time.Millisecond,
 		Refresh: func() (interface{}, string, error) {
 			err = f()
-			if err != nil {
-				return 42, "error", nil
+			if err == nil {
+				return 42, "success", nil
 			}
 
-			return 42, "success", nil
+			if rerr, ok := err.(RetryError); ok {
+				err = rerr.Err
+				return nil, "quit", err
+			}
+
+			return 42, "error", nil
 		},
 	}
 
 	c.WaitForState()
 	return err
 }
+
+// RetryError, if returned, will quit the retry immediately with the
+// Err.
+type RetryError struct {
+	Err error
+}
+
+func (e RetryError) Error() string {
+	return e.Err.Error()
+}

helper/resource/wait_test.go

@@ -37,3 +37,26 @@ func TestRetry_timeout(t *testing.T) {
 		t.Fatal("should error")
 	}
 }
+
+func TestRetry_error(t *testing.T) {
+	t.Parallel()
+
+	expected := fmt.Errorf("nope")
+	f := func() error {
+		return RetryError{expected}
+	}
+
+	errCh := make(chan error)
+	go func() {
+		errCh <- Retry(1*time.Second, f)
+	}()
+
+	select {
+	case err := <-errCh:
+		if err != expected {
+			t.Fatalf("bad: %#v", err)
+		}
+	case <-time.After(5 * time.Second):
+		t.Fatal("timeout")
+	}
+}