--- /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 fmt
+
+import (
+ "errors"
+ "strings"
+)
+
+// 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 errors.Wrapper
+// with an Unwrap method returning it.
+func Errorf(format string, a ...interface{}) error {
+ err, wrap := lastError(format, a)
+ if err == nil {
+ return &noWrapError{Sprintf(format, a...), nil, errors.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 := Sprintf(format[:len(format)-len(": %s")], a[:len(a)-1]...)
+ if wrap {
+ return &wrapError{msg, err, errors.Caller(1)}
+ }
+ return &noWrapError{msg, err, errors.Caller(1)}
+}
+
+func lastError(format string, a []interface{}) (err error, wrap bool) {
+ wrap = strings.HasSuffix(format, ": %w")
+ if !wrap &&
+ !strings.HasSuffix(format, ": %s") &&
+ !strings.HasSuffix(format, ": %v") {
+ return nil, false
+ }
+
+ if len(a) == 0 {
+ return nil, false
+ }
+
+ err, ok := a[len(a)-1].(error)
+ if !ok {
+ return nil, false
+ }
+
+ return err, wrap
+}
+
+type noWrapError struct {
+ msg string
+ err error
+ frame errors.Frame
+}
+
+func (e *noWrapError) Error() string {
+ return Sprint(e)
+}
+
+func (e *noWrapError) FormatError(p errors.Printer) (next error) {
+ p.Print(e.msg)
+ e.frame.Format(p)
+ return e.err
+}
+
+type wrapError struct {
+ msg string
+ err error
+ frame errors.Frame
+}
+
+func (e *wrapError) Error() string {
+ return Sprint(e)
+}
+
+func (e *wrapError) FormatError(p errors.Printer) (next error) {
+ p.Print(e.msg)
+ e.frame.Format(p)
+ return e.err
+}
+
+func (e *wrapError) Unwrap() error {
+ return e.err
+}
+
+func fmtError(p *pp, verb rune, err error) (handled bool) {
+ var (
+ sep = " " // separator before next error
+ w = p // print buffer where error text is written
+ )
+ switch {
+ // Note that this switch must match the preference order
+ // for ordinary string printing (%#v before %+v, and so on).
+
+ case p.fmt.sharpV:
+ if stringer, ok := p.arg.(GoStringer); ok {
+ // Print the result of GoString unadorned.
+ p.fmt.fmtS(stringer.GoString())
+ return true
+ }
+ return false
+
+ case p.fmt.plusV:
+ sep = "\n - "
+ w.fmt.fmtFlags = fmtFlags{plusV: p.fmt.plusV} // only keep detail flag
+
+ // The width or precision of a detailed view could be the number of
+ // errors to print from a list.
+
+ default:
+ // Use an intermediate buffer in the rare cases that precision,
+ // truncation, or one of the alternative verbs (q, x, and X) are
+ // specified.
+ switch verb {
+ case 's', 'v':
+ if (!w.fmt.widPresent || w.fmt.wid == 0) && !w.fmt.precPresent {
+ break
+ }
+ fallthrough
+ case 'q', 'x', 'X':
+ w = newPrinter()
+ defer w.free()
+ default:
+ w.badVerb(verb)
+ return true
+ }
+ }
+
+loop:
+ for {
+ w.fmt.inDetail = false
+ switch v := err.(type) {
+ case errors.Formatter:
+ err = v.FormatError((*errPP)(w))
+ case Formatter:
+ if w.fmt.plusV {
+ v.Format((*errPPState)(w), 'v') // indent new lines
+ } else {
+ v.Format(w, 'v') // do not indent new lines
+ }
+ break loop
+ default:
+ w.fmtString(v.Error(), 's')
+ break loop
+ }
+ if err == nil {
+ break
+ }
+ if w.fmt.needColon || !p.fmt.plusV {
+ w.buf.WriteByte(':')
+ w.fmt.needColon = false
+ }
+ w.buf.WriteString(sep)
+ w.fmt.inDetail = false
+ w.fmt.needNewline = false
+ }
+
+ if w != p {
+ p.fmtString(string(w.buf), verb)
+ }
+ return true
+}
+
+var detailSep = []byte("\n ")
+
+// errPPState wraps a pp to implement State with indentation. It is used
+// for errors implementing fmt.Formatter.
+type errPPState pp
+
+func (p *errPPState) Width() (wid int, ok bool) { return (*pp)(p).Width() }
+func (p *errPPState) Precision() (prec int, ok bool) { return (*pp)(p).Precision() }
+func (p *errPPState) Flag(c int) bool { return (*pp)(p).Flag(c) }
+
+func (p *errPPState) Write(b []byte) (n int, err error) {
+ if p.fmt.plusV {
+ if len(b) == 0 {
+ return 0, nil
+ }
+ if p.fmt.inDetail && p.fmt.needColon {
+ p.fmt.needNewline = true
+ if b[0] == '\n' {
+ b = b[1:]
+ }
+ }
+ k := 0
+ for i, c := range b {
+ if p.fmt.needNewline {
+ if p.fmt.inDetail && p.fmt.needColon {
+ p.buf.WriteByte(':')
+ p.fmt.needColon = false
+ }
+ p.buf.Write(detailSep)
+ p.fmt.needNewline = false
+ }
+ if c == '\n' {
+ p.buf.Write(b[k:i])
+ k = i + 1
+ p.fmt.needNewline = true
+ }
+ }
+ p.buf.Write(b[k:])
+ if !p.fmt.inDetail {
+ p.fmt.needColon = true
+ }
+ } else if !p.fmt.inDetail {
+ p.buf.Write(b)
+ }
+ return len(b), nil
+
+}
+
+// errPP wraps a pp to implement an errors.Printer.
+type errPP pp
+
+func (p *errPP) Print(args ...interface{}) {
+ if !p.fmt.inDetail || p.fmt.plusV {
+ Fprint((*errPPState)(p), args...)
+ }
+}
+
+func (p *errPP) Printf(format string, args ...interface{}) {
+ if !p.fmt.inDetail || p.fmt.plusV {
+ Fprintf((*errPPState)(p), format, args...)
+ }
+}
+
+func (p *errPP) Detail() bool {
+ p.fmt.inDetail = true
+ return p.fmt.plusV
+}
--- /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 fmt_test
+
+import (
+ "errors"
+ "fmt"
+ "io"
+ "os"
+ "path"
+ "reflect"
+ "regexp"
+ "strconv"
+ "strings"
+ "testing"
+)
+
+func TestErrorf(t *testing.T) {
+ chained := &wrapped{"chained", nil}
+ chain := func(s ...string) (a []string) {
+ for _, s := range s {
+ a = append(a, cleanPath(s))
+ }
+ return a
+ }
+ noArgsWrap := "no args: %w" // avoid vet check
+ testCases := []struct {
+ got error
+ want []string
+ }{{
+ fmt.Errorf("no args"),
+ chain("no args/path.TestErrorf/path.go:xxx"),
+ }, {
+ fmt.Errorf(noArgsWrap),
+ chain("no args: %!w(MISSING)/path.TestErrorf/path.go:xxx"),
+ }, {
+ fmt.Errorf("nounwrap: %s", "simple"),
+ chain(`nounwrap: simple/path.TestErrorf/path.go:xxx`),
+ }, {
+ fmt.Errorf("nounwrap: %v", "simple"),
+ chain(`nounwrap: simple/path.TestErrorf/path.go:xxx`),
+ }, {
+ fmt.Errorf("%s failed: %v", "foo", chained),
+ chain("foo failed/path.TestErrorf/path.go:xxx",
+ "chained/somefile.go:xxx"),
+ }, {
+ fmt.Errorf("no wrap: %s", chained),
+ chain("no wrap/path.TestErrorf/path.go:xxx",
+ "chained/somefile.go:xxx"),
+ }, {
+ fmt.Errorf("%s failed: %w", "foo", chained),
+ chain("wraps:foo failed/path.TestErrorf/path.go:xxx",
+ "chained/somefile.go:xxx"),
+ }, {
+ fmt.Errorf("nowrapv: %v", chained),
+ chain("nowrapv/path.TestErrorf/path.go:xxx",
+ "chained/somefile.go:xxx"),
+ }, {
+ fmt.Errorf("wrapw: %w", chained),
+ chain("wraps:wrapw/path.TestErrorf/path.go:xxx",
+ "chained/somefile.go:xxx"),
+ }, {
+ fmt.Errorf("not wrapped: %+v", chained),
+ chain("not wrapped: chained: somefile.go:123/path.TestErrorf/path.go:xxx"),
+ }}
+ for i, tc := range testCases {
+ t.Run(strconv.Itoa(i)+"/"+path.Join(tc.want...), func(t *testing.T) {
+ got := errToParts(tc.got)
+ if !reflect.DeepEqual(got, tc.want) {
+ t.Errorf("Format:\n got: %+q\nwant: %+q", got, tc.want)
+ }
+
+ gotStr := tc.got.Error()
+ wantStr := fmt.Sprint(tc.got)
+ if gotStr != wantStr {
+ t.Errorf("Error:\n got: %+q\nwant: %+q", gotStr, wantStr)
+ }
+ })
+ }
+}
+
+func TestErrorFormatter(t *testing.T) {
+ testCases := []struct {
+ err error
+ fmt string
+ want string
+ regexp bool
+ }{{
+ err: errors.New("foo"),
+ fmt: "%+v",
+ want: "foo:" +
+ "\n fmt_test.TestErrorFormatter" +
+ "\n .+/fmt/errors_test.go:\\d\\d",
+ regexp: true,
+ }, {
+ err: &wrapped{"simple", nil},
+ fmt: "%s",
+ want: "simple",
+ }, {
+ err: &wrapped{"can't adumbrate elephant", outOfPeanuts{}},
+ fmt: "%s",
+ want: "can't adumbrate elephant: out of peanuts",
+ }, {
+ err: &wrapped{"a", &wrapped{"b", &wrapped{"c", nil}}},
+ fmt: "%s",
+ want: "a: b: c",
+ }, {
+ err: &wrapped{"simple", nil},
+ fmt: "%+v",
+ want: "simple:" +
+ "\n somefile.go:123",
+ }, {
+ err: &wrapped{"can't adumbrate elephant", outOfPeanuts{}},
+ fmt: "%+v",
+ want: "can't adumbrate elephant:" +
+ "\n somefile.go:123" +
+ "\n - out of peanuts:" +
+ "\n the elephant is on strike" +
+ "\n and the 12 monkeys" +
+ "\n are laughing",
+ }, {
+ err: &wrapped{"simple", nil},
+ fmt: "%#v",
+ want: "&fmt_test.wrapped{msg:\"simple\", err:error(nil)}",
+ }, {
+ err: ¬AFormatterError{},
+ fmt: "%+v",
+ want: "not a formatter",
+ }, {
+ err: &wrapped{"wrap", ¬AFormatterError{}},
+ fmt: "%+v",
+ want: "wrap:" +
+ "\n somefile.go:123" +
+ "\n - not a formatter",
+ }, {
+ err: &withFrameAndMore{frame: errors.Caller(0)},
+ fmt: "%+v",
+ want: "something:" +
+ "\n fmt_test.TestErrorFormatter" +
+ "\n .+/fmt/errors_test.go:\\d\\d\\d" +
+ "\n something more",
+ regexp: true,
+ }, {
+ err: fmtTwice("Hello World!"),
+ fmt: "%#v",
+ want: "2 times Hello World!",
+ }, {
+ err: &wrapped{"fallback", os.ErrNotExist},
+ fmt: "%s",
+ want: "fallback: file does not exist",
+ }, {
+ err: &wrapped{"fallback", os.ErrNotExist},
+ fmt: "%+v",
+ // Note: no colon after the last error, as there are no details.
+ want: "fallback:" +
+ "\n somefile.go:123" +
+ "\n - file does not exist:" +
+ "\n os.init.ializers" +
+ "\n .+/os/error.go:\\d\\d",
+ regexp: true,
+ }, {
+ err: &wrapped{"outer",
+ errors.Opaque(&wrapped{"mid",
+ &wrapped{"inner", nil}})},
+ fmt: "%s",
+ want: "outer: mid: inner",
+ }, {
+ err: &wrapped{"outer",
+ errors.Opaque(&wrapped{"mid",
+ &wrapped{"inner", nil}})},
+ fmt: "%+v",
+ want: "outer:" +
+ "\n somefile.go:123" +
+ "\n - mid:" +
+ "\n somefile.go:123" +
+ "\n - inner:" +
+ "\n somefile.go:123",
+ }, {
+ err: &wrapped{"new style", formatError("old style")},
+ fmt: "%v",
+ want: "new style: old style",
+ }, {
+ err: &wrapped{"new style", formatError("old style")},
+ fmt: "%q",
+ want: `"new style: old style"`,
+ }, {
+ err: &wrapped{"new style", formatError("old style")},
+ fmt: "%+v",
+ // Note the extra indentation.
+ // Colon for old style error is rendered by the fmt.Formatter
+ // implementation of the old-style error.
+ want: "new style:" +
+ "\n somefile.go:123" +
+ "\n - old style:" +
+ "\n otherfile.go:456",
+ }, {
+ err: &wrapped{"simple", nil},
+ fmt: "%-12s",
+ want: "simple ",
+ }, {
+ // Don't use formatting flags for detailed view.
+ err: &wrapped{"simple", nil},
+ fmt: "%+12v",
+ want: "simple:" +
+ "\n somefile.go:123",
+ }, {
+ err: &wrapped{"can't adumbrate elephant", outOfPeanuts{}},
+ fmt: "%+50s",
+ want: " can't adumbrate elephant: out of peanuts",
+ }, {
+ err: &wrapped{"café", nil},
+ fmt: "%q",
+ want: `"café"`,
+ }, {
+ err: &wrapped{"café", nil},
+ fmt: "%+q",
+ want: `"caf\u00e9"`,
+ }, {
+ err: &wrapped{"simple", nil},
+ fmt: "% x",
+ want: "73 69 6d 70 6c 65",
+ }, {
+ err: &wrapped{"msg with\nnewline",
+ &wrapped{"and another\none", nil}},
+ fmt: "%s",
+ want: "msg with" +
+ "\nnewline: and another" +
+ "\none",
+ }, {
+ err: &wrapped{"msg with\nnewline",
+ &wrapped{"and another\none", nil}},
+ fmt: "%+v",
+ want: "msg with" +
+ "\n newline:" +
+ "\n somefile.go:123" +
+ "\n - and another" +
+ "\n one:" +
+ "\n somefile.go:123",
+ }, {
+ err: wrapped{"", wrapped{"inner message", nil}},
+ fmt: "%+v",
+ want: "somefile.go:123" +
+ "\n - inner message:" +
+ "\n somefile.go:123",
+ }, {
+ err: detail{"empty detail", "", nil},
+ fmt: "%s",
+ want: "empty detail",
+ }, {
+ err: detail{"empty detail", "", nil},
+ fmt: "%+v",
+ want: "empty detail",
+ }, {
+ err: detail{"newline at start", "\nextra", nil},
+ fmt: "%s",
+ want: "newline at start",
+ }, {
+ err: detail{"newline at start", "\n extra", nil},
+ fmt: "%+v",
+ want: "newline at start:" +
+ "\n extra",
+ }, {
+ err: detail{"newline at start", "\nextra",
+ detail{"newline at start", "\nmore", nil}},
+ fmt: "%+v",
+ want: "newline at start:" +
+ "\n extra" +
+ "\n - newline at start:" +
+ "\n more",
+ }, {
+ err: detail{"two newlines at start", "\n\nextra",
+ detail{"two newlines at start", "\n\nmore", nil}},
+ fmt: "%+v",
+ want: "two newlines at start:" +
+ "\n " + // note the explicit space
+ "\n extra" +
+ "\n - two newlines at start:" +
+ "\n " +
+ "\n more",
+ }, {
+ err: &detail{"single newline", "\n", nil},
+ fmt: "%+v",
+ want: "single newline",
+ }, {
+ err: &detail{"single newline", "\n",
+ &detail{"single newline", "\n", nil}},
+ fmt: "%+v",
+ want: "single newline:" +
+ "\n - single newline",
+ }, {
+ err: &detail{"newline at end", "detail\n", nil},
+ fmt: "%+v",
+ want: "newline at end:" +
+ "\n detail",
+ }, {
+ err: &detail{"newline at end", "detail\n",
+ &detail{"newline at end", "detail\n", nil}},
+ fmt: "%+v",
+ want: "newline at end:" +
+ "\n detail" +
+ "\n - newline at end:" +
+ "\n detail",
+ }, {
+ err: &detail{"two newlines at end", "detail\n\n",
+ &detail{"two newlines at end", "detail\n\n", nil}},
+ fmt: "%+v",
+ want: "two newlines at end:" +
+ "\n detail" +
+ "\n " +
+ "\n - two newlines at end:" +
+ "\n detail" +
+ "\n ", // note the additional space
+ }, {
+ err: nil,
+ fmt: "%+v",
+ want: "<nil>",
+ }, {
+ err: (*wrapped)(nil),
+ fmt: "%+v",
+ want: "<nil>",
+ }, {
+ err: &wrapped{"simple", nil},
+ fmt: "%T",
+ want: "*fmt_test.wrapped",
+ }, {
+ err: &wrapped{"simple", nil},
+ fmt: "%🤪",
+ want: "%!🤪(*fmt_test.wrapped=&{simple <nil>})",
+ }, {
+ err: formatError("use fmt.Formatter"),
+ fmt: "%#v",
+ want: "use fmt.Formatter",
+ }, {
+ err: wrapped{"using errors.Formatter",
+ formatError("use fmt.Formatter")},
+ fmt: "%#v",
+ want: "fmt_test.wrapped{msg:\"using errors.Formatter\", err:\"use fmt.Formatter\"}",
+ }, {
+ err: fmtTwice("%s %s", "ok", panicValue{}),
+ fmt: "%s",
+ want: "ok %!s(PANIC=String method: panic)/ok %!s(PANIC=String method: panic)",
+ }, {
+ err: fmtTwice("%o %s", panicValue{}, "ok"),
+ fmt: "%s",
+ want: "{} ok/{} ok",
+ }}
+ for i, tc := range testCases {
+ t.Run(fmt.Sprintf("%d/%s", i, tc.fmt), func(t *testing.T) {
+ got := fmt.Sprintf(tc.fmt, tc.err)
+ var ok bool
+ if tc.regexp {
+ var err error
+ ok, err = regexp.MatchString(tc.want+"$", got)
+ if err != nil {
+ t.Fatal(err)
+ }
+ } else {
+ ok = got == tc.want
+ }
+ if !ok {
+ t.Errorf("\n got: %q\nwant: %q", got, tc.want)
+ }
+ })
+ }
+}
+
+var _ errors.Formatter = wrapped{}
+
+type wrapped struct {
+ msg string
+ err error
+}
+
+func (e wrapped) Error() string { return fmt.Sprint(e) }
+
+func (e wrapped) FormatError(p errors.Printer) (next error) {
+ p.Print(e.msg)
+ p.Detail()
+ p.Print("somefile.go:123")
+ return e.err
+}
+
+var _ errors.Formatter = outOfPeanuts{}
+
+type outOfPeanuts struct{}
+
+func (e outOfPeanuts) Error() string { return fmt.Sprint(e) }
+
+func (e outOfPeanuts) Format(fmt.State, rune) {
+ panic("should never be called by one of the tests")
+}
+
+func (outOfPeanuts) FormatError(p errors.Printer) (next error) {
+ p.Printf("out of %s", "peanuts")
+ p.Detail()
+ p.Print("the elephant is on strike\n")
+ p.Printf("and the %d monkeys\nare laughing", 12)
+ return nil
+}
+
+type withFrameAndMore struct {
+ frame errors.Frame
+}
+
+func (e *withFrameAndMore) Error() string { return fmt.Sprint(e) }
+
+func (e *withFrameAndMore) FormatError(p errors.Printer) (next error) {
+ p.Print("something")
+ if p.Detail() {
+ e.frame.Format(p)
+ p.Print("something more")
+ }
+ return nil
+}
+
+type notAFormatterError struct{}
+
+func (e notAFormatterError) Error() string { return "not a formatter" }
+
+type detail struct {
+ msg string
+ detail string
+ next error
+}
+
+func (e detail) Error() string { return fmt.Sprint(e) }
+
+func (e detail) FormatError(p errors.Printer) (next error) {
+ p.Print(e.msg)
+ p.Detail()
+ p.Print(e.detail)
+ return e.next
+}
+
+// formatError is an error implementing Format instead of errors.Formatter.
+// The implementation mimics the implementation of github.com/pkg/errors.
+type formatError string
+
+func (e formatError) Error() string { return string(e) }
+
+func (e formatError) Format(s fmt.State, verb rune) {
+ // Body based on pkg/errors/errors.go
+ switch verb {
+ case 'v':
+ if s.Flag('+') {
+ io.WriteString(s, string(e))
+ fmt.Fprintf(s, ":\n%s", "otherfile.go:456")
+ return
+ }
+ fallthrough
+ case 's':
+ io.WriteString(s, string(e))
+ case 'q':
+ fmt.Fprintf(s, "%q", string(e))
+ }
+}
+
+func (e formatError) GoString() string {
+ panic("should never be called")
+}
+
+type fmtTwiceErr struct {
+ format string
+ args []interface{}
+}
+
+func fmtTwice(format string, a ...interface{}) error {
+ return fmtTwiceErr{format, a}
+}
+
+func (e fmtTwiceErr) Error() string { return fmt.Sprint(e) }
+
+func (e fmtTwiceErr) FormatError(p errors.Printer) (next error) {
+ p.Printf(e.format, e.args...)
+ p.Print("/")
+ p.Printf(e.format, e.args...)
+ return nil
+}
+
+func (e fmtTwiceErr) GoString() string {
+ return "2 times " + fmt.Sprintf(e.format, e.args...)
+}
+
+type panicValue struct{}
+
+func (panicValue) String() string { panic("panic") }
+
+var rePath = regexp.MustCompile(`( [^ ]*)fmt.*test\.`)
+var reLine = regexp.MustCompile(":[0-9]*\n?$")
+
+func cleanPath(s string) string {
+ s = rePath.ReplaceAllString(s, "/path.")
+ s = reLine.ReplaceAllString(s, ":xxx")
+ s = strings.Replace(s, "\n ", "", -1)
+ s = strings.Replace(s, " /", "/", -1)
+ return s
+}
+
+func errToParts(err error) (a []string) {
+ for err != nil {
+ var p testPrinter
+ if errors.Unwrap(err) != nil {
+ p.str += "wraps:"
+ }
+ f, ok := err.(errors.Formatter)
+ if !ok {
+ a = append(a, err.Error())
+ break
+ }
+ err = f.FormatError(&p)
+ a = append(a, cleanPath(p.str))
+ }
+ return a
+
+}
+
+type testPrinter struct {
+ str string
+}
+
+func (p *testPrinter) Print(a ...interface{}) {
+ p.str += fmt.Sprint(a...)
+}
+
+func (p *testPrinter) Printf(format string, a ...interface{}) {
+ p.str += fmt.Sprintf(format, a...)
+}
+
+func (p *testPrinter) Detail() bool {
+ p.str += " /"
+ return true
+}