rc: factor rc.Error out of rcserver for re-use in librclone #4891

fs/rc/params.go

@@ -279,3 +279,26 @@ func (p Params) GetDuration(key string) (time.Duration, error) {
 	}
 	return duration, nil
 }
+
+// Error creates the standard response for an errored rc call using an
+// rc.Param from a path, input Params, error and a suggested HTTP
+// response code.
+//
+// It returns a Params and an updated status code
+func Error(path string, in Params, err error, status int) (Params, int) {
+	// Adjust the status code for some well known errors
+	errOrig := errors.Cause(err)
+	switch {
+	case errOrig == fs.ErrorDirNotFound || errOrig == fs.ErrorObjectNotFound:
+		status = http.StatusNotFound
+	case IsErrParamInvalid(err) || IsErrParamNotFound(err):
+		status = http.StatusBadRequest
+	}
+	result := Params{
+		"status": status,
+		"error":  err.Error(),
+		"input":  in,
+		"path":   path,
+	}
+	return result, status
+}

fs/rc/rcserver/rcserver.go

@@ -169,21 +169,9 @@ func (s *Server) Serve() error {
 // writeError writes a formatted error to the output
 func writeError(path string, in rc.Params, w http.ResponseWriter, err error, status int) {
 	fs.Errorf(nil, "rc: %q: error: %v", path, err)
-	// Adjust the error return for some well known errors
+	params, status := rc.Error(path, in, err, status)
-	errOrig := errors.Cause(err)
-	switch {
-	case errOrig == fs.ErrorDirNotFound || errOrig == fs.ErrorObjectNotFound:
-		status = http.StatusNotFound
-	case rc.IsErrParamInvalid(err) || rc.IsErrParamNotFound(err):
-		status = http.StatusBadRequest
-	}
 	w.WriteHeader(status)
-	err = rc.WriteJSON(w, rc.Params{
+	err = rc.WriteJSON(w, params)
-		"status": status,
-		"error":  err.Error(),
-		"input":  in,
-		"path":   path,
-	})
 	if err != nil {
 		// can't return the error at this point
 		fs.Errorf(nil, "rc: writeError: failed to write JSON output from %#v: %v", in, err)