--- /dev/null
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package xerrors
+
+import (
+ "fmt"
+ "strings"
+ "unicode"
+ "unicode/utf8"
+
+ "golang.org/x/xerrors/internal"
+)
+
+const percentBangString = "%!"
+
+// Errorf formats according to a format specifier and returns the string as a
+// value that satisfies error.
+//
+// The returned error includes the file and line number of the caller when
+// formatted with additional detail enabled. If the last argument is an error
+// the returned error's Format method will return it if the format string ends
+// with ": %s", ": %v", or ": %w". If the last argument is an error and the
+// format string ends with ": %w", the returned error implements an Unwrap
+// method returning it.
+//
+// If the format specifier includes a %w verb with an error operand in a
+// position other than at the end, the returned error will still implement an
+// Unwrap method returning the operand, but the error's Format method will not
+// return the wrapped error.
+//
+// It is invalid to include more than one %w verb or to supply it with an
+// operand that does not implement the error interface. The %w verb is otherwise
+// a synonym for %v.
+func Errorf(format string, a ...interface{}) error {
+ format = formatPlusW(format)
+ // Support a ": %[wsv]" suffix, which works well with xerrors.Formatter.
+ wrap := strings.HasSuffix(format, ": %w")
+ idx, format2, ok := parsePercentW(format)
+ percentWElsewhere := !wrap && idx >= 0
+ if !percentWElsewhere && (wrap || strings.HasSuffix(format, ": %s") || strings.HasSuffix(format, ": %v")) {
+ err := errorAt(a, len(a)-1)
+ if err == nil {
+ return &noWrapError{fmt.Sprintf(format, a...), nil, Caller(1)}
+ }
+ // TODO: this is not entirely correct. The error value could be
+ // printed elsewhere in format if it mixes numbered with unnumbered
+ // substitutions. With relatively small changes to doPrintf we can
+ // have it optionally ignore extra arguments and pass the argument
+ // list in its entirety.
+ msg := fmt.Sprintf(format[:len(format)-len(": %s")], a[:len(a)-1]...)
+ frame := Frame{}
+ if internal.EnableTrace {
+ frame = Caller(1)
+ }
+ if wrap {
+ return &wrapError{msg, err, frame}
+ }
+ return &noWrapError{msg, err, frame}
+ }
+ // Support %w anywhere.
+ // TODO: don't repeat the wrapped error's message when %w occurs in the middle.
+ msg := fmt.Sprintf(format2, a...)
+ if idx < 0 {
+ return &noWrapError{msg, nil, Caller(1)}
+ }
+ err := errorAt(a, idx)
+ if !ok || err == nil {
+ // Too many %ws or argument of %w is not an error. Approximate the Go
+ // 1.13 fmt.Errorf message.
+ return &noWrapError{fmt.Sprintf("%sw(%s)", percentBangString, msg), nil, Caller(1)}
+ }
+ frame := Frame{}
+ if internal.EnableTrace {
+ frame = Caller(1)
+ }
+ return &wrapError{msg, err, frame}
+}
+
+func errorAt(args []interface{}, i int) error {
+ if i < 0 || i >= len(args) {
+ return nil
+ }
+ err, ok := args[i].(error)
+ if !ok {
+ return nil
+ }
+ return err
+}
+
+// formatPlusW is used to avoid the vet check that will barf at %w.
+func formatPlusW(s string) string {
+ return s
+}
+
+// Return the index of the only %w in format, or -1 if none.
+// Also return a rewritten format string with %w replaced by %v, and
+// false if there is more than one %w.
+// TODO: handle "%[N]w".
+func parsePercentW(format string) (idx int, newFormat string, ok bool) {
+ // Loosely copied from golang.org/x/tools/go/analysis/passes/printf/printf.go.
+ idx = -1
+ ok = true
+ n := 0
+ sz := 0
+ var isW bool
+ for i := 0; i < len(format); i += sz {
+ if format[i] != '%' {
+ sz = 1
+ continue
+ }
+ // "%%" is not a format directive.
+ if i+1 < len(format) && format[i+1] == '%' {
+ sz = 2
+ continue
+ }
+ sz, isW = parsePrintfVerb(format[i:])
+ if isW {
+ if idx >= 0 {
+ ok = false
+ } else {
+ idx = n
+ }
+ // "Replace" the last character, the 'w', with a 'v'.
+ p := i + sz - 1
+ format = format[:p] + "v" + format[p+1:]
+ }
+ n++
+ }
+ return idx, format, ok
+}
+
+// Parse the printf verb starting with a % at s[0].
+// Return how many bytes it occupies and whether the verb is 'w'.
+func parsePrintfVerb(s string) (int, bool) {
+ // Assume only that the directive is a sequence of non-letters followed by a single letter.
+ sz := 0
+ var r rune
+ for i := 1; i < len(s); i += sz {
+ r, sz = utf8.DecodeRuneInString(s[i:])
+ if unicode.IsLetter(r) {
+ return i + sz, r == 'w'
+ }
+ }
+ return len(s), false
+}
+
+type noWrapError struct {
+ msg string
+ err error
+ frame Frame
+}
+
+func (e *noWrapError) Error() string {
+ return fmt.Sprint(e)
+}
+
+func (e *noWrapError) Format(s fmt.State, v rune) { FormatError(e, s, v) }
+
+func (e *noWrapError) FormatError(p Printer) (next error) {
+ p.Print(e.msg)
+ e.frame.Format(p)
+ return e.err
+}
+
+type wrapError struct {
+ msg string
+ err error
+ frame Frame
+}
+
+func (e *wrapError) Error() string {
+ return fmt.Sprint(e)
+}
+
+func (e *wrapError) Format(s fmt.State, v rune) { FormatError(e, s, v) }
+
+func (e *wrapError) FormatError(p Printer) (next error) {
+ p.Print(e.msg)
+ e.frame.Format(p)
+ return e.err
+}
+
+func (e *wrapError) Unwrap() error {
+ return e.err
+}
projects / dotfiles / .git / blobdiff