109 lines
2.6 KiB
Go
109 lines
2.6 KiB
Go
// Copyright 2018 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package xerrors
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import (
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"fmt"
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"strings"
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"golang.org/x/xerrors/internal"
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)
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// Errorf formats according to a format specifier and returns the string as a
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// value that satisfies error.
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//
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// The returned error includes the file and line number of the caller when
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// formatted with additional detail enabled. If the last argument is an error
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// the returned error's Format method will return it if the format string ends
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// with ": %s", ": %v", or ": %w". If the last argument is an error and the
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// format string ends with ": %w", the returned error implements Wrapper
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// with an Unwrap method returning it.
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func Errorf(format string, a ...interface{}) error {
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err, wrap := lastError(format, a)
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format = formatPlusW(format)
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if err == nil {
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return &noWrapError{fmt.Sprintf(format, a...), nil, Caller(1)}
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}
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// TODO: this is not entirely correct. The error value could be
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// printed elsewhere in format if it mixes numbered with unnumbered
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// substitutions. With relatively small changes to doPrintf we can
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// have it optionally ignore extra arguments and pass the argument
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// list in its entirety.
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msg := fmt.Sprintf(format[:len(format)-len(": %s")], a[:len(a)-1]...)
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frame := Frame{}
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if internal.EnableTrace {
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frame = Caller(1)
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}
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if wrap {
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return &wrapError{msg, err, frame}
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}
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return &noWrapError{msg, err, frame}
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}
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// formatPlusW is used to avoid the vet check that will barf at %w.
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func formatPlusW(s string) string {
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return s
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}
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func lastError(format string, a []interface{}) (err error, wrap bool) {
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wrap = strings.HasSuffix(format, ": %w")
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if !wrap &&
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!strings.HasSuffix(format, ": %s") &&
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!strings.HasSuffix(format, ": %v") {
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return nil, false
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}
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if len(a) == 0 {
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return nil, false
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}
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err, ok := a[len(a)-1].(error)
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if !ok {
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return nil, false
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}
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return err, wrap
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}
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type noWrapError struct {
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msg string
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err error
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frame Frame
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}
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func (e *noWrapError) Error() string {
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return fmt.Sprint(e)
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}
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func (e *noWrapError) Format(s fmt.State, v rune) { FormatError(e, s, v) }
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func (e *noWrapError) FormatError(p Printer) (next error) {
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p.Print(e.msg)
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e.frame.Format(p)
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return e.err
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}
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type wrapError struct {
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msg string
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err error
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frame Frame
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}
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func (e *wrapError) Error() string {
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return fmt.Sprint(e)
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}
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func (e *wrapError) Format(s fmt.State, v rune) { FormatError(e, s, v) }
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func (e *wrapError) FormatError(p Printer) (next error) {
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p.Print(e.msg)
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e.frame.Format(p)
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return e.err
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}
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func (e *wrapError) Unwrap() error {
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return e.err
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}
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