ostree: rename errors and introduce ParameterComboError

Shorter and clearer error types.
- InvalidParameterError is now RefError.  It is returned when a ref (the
  new ref or the parent ref) is invalid.
- The ResolveRefError is not renamed.  It is returned when a ref can't
  be resolved (e.g., ref not found at URL).

New error type ParameterComboError.  It is returned when a parent ref is
specified but no URL, which is an invalid parameter combination.

internal/cloudapi/v2/v2.go

@@ -286,7 +286,7 @@ func (h *apiHandlers) PostCompose(ctx echo.Context) error {
 		}
 		if imageOptions.OSTree, err = ostree.ResolveParams(ostreeOptions, imageType.OSTreeRef()); err != nil {
 			switch v := err.(type) {
-			case ostree.InvalidParameterError:
+			case ostree.RefError:
 				return HTTPError(ErrorInvalidOSTreeRef)
 			case ostree.ResolveRefError:
 				return HTTPErrorWithInternal(ErrorInvalidOSTreeRepo, v)

internal/ostree/errors.go

@@ -20,16 +20,28 @@ func NewResolveRefError(msg string, args ...interface{}) ResolveRefError {
 
 // InvalidParamsError is returned when a parameter is invalid (e.g., malformed
 // or contains illegal characters).
-type InvalidParameterError struct {
+type RefError struct {
 	msg string
 }
 
-func (e InvalidParameterError) Error() string {
+func (e RefError) Error() string {
 	return e.msg
 }
 
-// NewInvalidParameterError creates and returns a new InvalidParameterError
+// NewRefError creates and returns a new InvalidParameterError
 // with a given formatted message.
-func NewInvalidParameterError(msg string, args ...interface{}) InvalidParameterError {
-	return InvalidParameterError{msg: fmt.Sprintf(msg, args...)}
+func NewRefError(msg string, args ...interface{}) RefError {
+	return RefError{msg: fmt.Sprintf(msg, args...)}
+}
+
+type ParameterComboError struct {
+	msg string
+}
+
+func (e ParameterComboError) Error() string {
+	return e.msg
+}
+
+func NewParameterComboError(msg string, args ...interface{}) ParameterComboError {
+	return ParameterComboError{msg: fmt.Sprintf(msg, args...)}
 }

internal/ostree/ostree.go

@@ -62,17 +62,17 @@ func ResolveParams(params RequestParams, defaultRef string) (RequestParams, erro
 	if resolved.Ref == "" {
 		resolved.Ref = defaultRef
 	} else if !VerifyRef(params.Ref) { // only verify if specified in params
-		return resolved, NewInvalidParameterError("Invalid ostree ref %q", params.Ref)
+		return resolved, NewRefError("Invalid ostree ref %q", params.Ref)
 	}
 
 	if params.Parent != "" {
 		// parent must also be a valid ref
 		if !VerifyRef(params.Parent) {
-			return resolved, NewInvalidParameterError("Invalid ostree parent ref %q", params.Parent)
+			return resolved, NewRefError("Invalid ostree parent ref %q", params.Parent)
 		}
 		if params.URL == "" {
 			// specifying parent ref also requires URL
-			return resolved, NewInvalidParameterError("ostree parent ref specified, but no URL to retrieve it")
+			return resolved, NewParameterComboError("ostree parent ref specified, but no URL to retrieve it")
 		}
 	}