1 files changed, 65 insertions, 0 deletions
diff --git a/modules/util/error.go b/modules/util/error.go
new file mode 100644
index 00000000..0f359714
--- /dev/null
+++ b/modules/util/error.go
@@ -0,0 +1,65 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package util
+
+import (
+	"errors"
+	"fmt"
+)
+
+// Common Errors forming the base of our error system
+//
+// Many Errors returned by Gitea can be tested against these errors
+// using errors.Is.
+var (
+	ErrInvalidArgument  = errors.New("invalid argument")
+	ErrPermissionDenied = errors.New("permission denied")
+	ErrAlreadyExist     = errors.New("resource already exists")
+	ErrNotExist         = errors.New("resource does not exist")
+)
+
+// SilentWrap provides a simple wrapper for a wrapped error where the wrapped error message plays no part in the error message
+// Especially useful for "untyped" errors created with "errors.New(…)" that can be classified as 'invalid argument', 'permission denied', 'exists already', or 'does not exist'
+type SilentWrap struct {
+	Message string
+	Err     error
+}
+
+// Error returns the message
+func (w SilentWrap) Error() string {
+	return w.Message
+}
+
+// Unwrap returns the underlying error
+func (w SilentWrap) Unwrap() error {
+	return w.Err
+}
+
+// NewSilentWrapErrorf returns an error that formats as the given text but unwraps as the provided error
+func NewSilentWrapErrorf(unwrap error, message string, args ...any) error {
+	if len(args) == 0 {
+		return SilentWrap{Message: message, Err: unwrap}
+	}
+	return SilentWrap{Message: fmt.Sprintf(message, args...), Err: unwrap}
+}
+
+// NewInvalidArgumentErrorf returns an error that formats as the given text but unwraps as an ErrInvalidArgument
+func NewInvalidArgumentErrorf(message string, args ...any) error {
+	return NewSilentWrapErrorf(ErrInvalidArgument, message, args...)
+}
+
+// NewPermissionDeniedErrorf returns an error that formats as the given text but unwraps as an ErrPermissionDenied
+func NewPermissionDeniedErrorf(message string, args ...any) error {
+	return NewSilentWrapErrorf(ErrPermissionDenied, message, args...)
+}
+
+// NewAlreadyExistErrorf returns an error that formats as the given text but unwraps as an ErrAlreadyExist
+func NewAlreadyExistErrorf(message string, args ...any) error {
+	return NewSilentWrapErrorf(ErrAlreadyExist, message, args...)
+}
+
+// NewNotExistErrorf returns an error that formats as the given text but unwraps as an ErrNotExist
+func NewNotExistErrorf(message string, args ...any) error {
+	return NewSilentWrapErrorf(ErrNotExist, message, args...)
+}