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feat: add TextFlag
* Added `TextFlag` which supports setting values for types that satisfies the `encoding.TextMarshaller` and `encoding.TextUnmarshaller` which is very handy when you want to set log levels or string-like types that satifies the interfaces. Fixes: #2051 Signed-off-by: Tobias Dahlberg <[email protected]>
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‎flag_text.go‎

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package cli
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import (
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"encoding"
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)
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type TextMarshalUnmarshaler interface {
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encoding.TextMarshaler
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encoding.TextUnmarshaler
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}
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// TextFlag enables you to set types that satisfies [TextMarshalUnmarshaler] using flags such as log levels.
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type TextFlag = FlagBase[TextMarshalUnmarshaler, NoConfig, TextValue]
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type TextValue struct {
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Value TextMarshalUnmarshaler
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}
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func (f TextValue) String() string {
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text, err := f.Value.MarshalText()
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if err != nil {
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return ""
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}
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return string(text)
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}
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func (f TextValue) Set(s string) error {
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return f.Value.UnmarshalText([]byte(s))
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}
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func (f TextValue) Get() any {
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return f.Value
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}
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func (f TextValue) Create(v TextMarshalUnmarshaler, p *TextMarshalUnmarshaler, _ NoConfig) Value {
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pp := *p
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if v != nil {
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if b, err := v.MarshalText(); err == nil {
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_ = pp.UnmarshalText(b)
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}
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}
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return &TextValue{
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Value: pp,
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}
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}
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func (f TextValue) ToString(v TextMarshalUnmarshaler) string {
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text, _ := v.MarshalText()
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return string(text)
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}

‎flag_text_test.go‎

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package cli
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import (
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"encoding"
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"errors"
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"io"
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"log/slog"
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"slices"
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"testing"
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"github.com/stretchr/testify/assert"
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"github.com/stretchr/testify/require"
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)
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type badMarshaller struct{}
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func (badMarshaller) UnmarshalText(_ []byte) error {
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return nil
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}
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func (badMarshaller) MarshalText() ([]byte, error) {
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return nil, errors.New("bad")
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}
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func ptr[T any](v T) *T {
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return &v
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}
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func TestTextFlag(t *testing.T) {
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tests := []struct {
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name string
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flag *TextFlag
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args []string
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want string
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wantErr bool
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}{
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{
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name: "empty",
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flag: &TextFlag{
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Name: "log-level",
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Value: &slog.LevelVar{},
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Destination: ptr[TextMarshalUnmarshaler](&slog.LevelVar{}),
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},
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want: "INFO",
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},
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{
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name: "info",
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flag: &TextFlag{
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Name: "log-level",
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Value: &slog.LevelVar{},
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Destination: ptr[TextMarshalUnmarshaler](&slog.LevelVar{}),
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Validator: func(v TextMarshalUnmarshaler) error {
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text, err := v.MarshalText()
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if err != nil {
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return err
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}
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if !slices.Equal(text, []byte("INFO")) {
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return errors.New("expected \"INFO\"")
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}
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return nil
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},
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},
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args: []string{"--log-level", "info"},
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want: "INFO",
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},
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{
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name: "debug",
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flag: &TextFlag{
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Name: "log-level",
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Value: &slog.LevelVar{},
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Destination: ptr[TextMarshalUnmarshaler](&slog.LevelVar{}),
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},
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args: []string{"--log-level", "debug"},
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want: "DEBUG",
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},
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{
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name: "invalid",
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flag: &TextFlag{
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Name: "log-level",
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Value: &slog.LevelVar{},
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Destination: ptr[TextMarshalUnmarshaler](&slog.LevelVar{}),
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},
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args: []string{"--log-level", "invalid"},
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want: "INFO",
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wantErr: true,
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},
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{
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name: "bad_marshaller",
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flag: &TextFlag{
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Name: "text",
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Value: &badMarshaller{},
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Destination: ptr[TextMarshalUnmarshaler](&badMarshaller{}),
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},
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args: []string{"--text", "foo"},
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wantErr: true,
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},
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{
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name: "default",
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flag: &TextFlag{
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Name: "log-level",
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Value: func() *slog.LevelVar {
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var l slog.LevelVar
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l.Set(slog.LevelWarn)
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return &l
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}(),
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Destination: ptr[TextMarshalUnmarshaler](&slog.LevelVar{}),
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},
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args: []string{},
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want: "WARN",
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},
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{
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name: "override_default",
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flag: &TextFlag{
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Name: "log-level",
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Value: func() *slog.LevelVar {
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var l slog.LevelVar
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l.Set(slog.LevelWarn)
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return &l
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}(),
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Destination: ptr[TextMarshalUnmarshaler](&slog.LevelVar{}),
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},
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args: []string{"--log-level", "error"},
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want: "ERROR",
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},
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}
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t.Parallel()
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for _, tt := range tests {
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t.Parallel()
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t.Run(tt.name, func(t *testing.T) {
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cmd := &Command{
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Name: tt.name,
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Flags: []Flag{tt.flag},
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Writer: io.Discard,
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ErrWriter: io.Discard,
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}
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err := cmd.Run(buildTestContext(t), append([]string{"mock"}, tt.args...))
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if err != nil && !tt.wantErr {
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require.NoError(t, err)
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return
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} else if err != nil {
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return
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}
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var got []byte
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got, err = tt.flag.Get().(encoding.TextMarshaler).MarshalText()
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if tt.wantErr {
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require.Error(t, err)
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return
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}
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assert.Equal(t, tt.want, string(got))
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})
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}
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}

‎godoc-current.txt‎

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@@ -1140,6 +1140,29 @@ type SuggestCommandFunc func(commands []*Command, provided string) string
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type SuggestFlagFunc func(flags []Flag, provided string, hideHelp bool) string
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type TextFlag = FlagBase[TextMarshalUnmarshaler, NoConfig, TextValue]
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TextFlag enables you to set types that satisfies TextMarshalUnmarshaler
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using flags such as log levels.
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type TextMarshalUnmarshaler interface {
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encoding.TextMarshaler
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encoding.TextUnmarshaler
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}
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type TextValue struct {
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Value TextMarshalUnmarshaler
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}
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func (f TextValue) Create(v TextMarshalUnmarshaler, p *TextMarshalUnmarshaler, _ NoConfig) Value
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func (f TextValue) Get() any
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func (f TextValue) Set(s string) error
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func (f TextValue) String() string
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func (f TextValue) ToString(v TextMarshalUnmarshaler) string
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type TimestampArg = ArgumentBase[time.Time, TimestampConfig, timestampValue]
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type TimestampConfig struct {

‎testdata/godoc-v3.x.txt‎

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@@ -1140,6 +1140,29 @@ type SuggestCommandFunc func(commands []*Command, provided string) string
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11411141
type SuggestFlagFunc func(flags []Flag, provided string, hideHelp bool) string
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type TextFlag = FlagBase[TextMarshalUnmarshaler, NoConfig, TextValue]
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TextFlag enables you to set types that satisfies TextMarshalUnmarshaler
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using flags such as log levels.
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type TextMarshalUnmarshaler interface {
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encoding.TextMarshaler
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encoding.TextUnmarshaler
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}
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type TextValue struct {
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Value TextMarshalUnmarshaler
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}
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func (f TextValue) Create(v TextMarshalUnmarshaler, p *TextMarshalUnmarshaler, _ NoConfig) Value
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func (f TextValue) Get() any
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func (f TextValue) Set(s string) error
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func (f TextValue) String() string
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func (f TextValue) ToString(v TextMarshalUnmarshaler) string
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type TimestampArg = ArgumentBase[time.Time, TimestampConfig, timestampValue]
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type TimestampConfig struct {

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