flagtype

At a glance

Each symbol links to its godoc entry, the canonical reference.

FUNCTIONS
    func StringSlice() flag.Value
    func Enum(allowed ...string) flag.Value
    func EnumDefault(defaultVal string, allowed []string) flag.Value
    func StringMap() flag.Value
    func URL() flag.Value
    func Regexp() flag.Value

Patterns

Register a value with f.Var(), retrieve it with the matching cli.GetFlag[T]. The full set, in one place:

cmd := &cli.Command{
    Name: "fetch",
    Flags: cli.FlagsFunc(func(f *flag.FlagSet) {
        f.Var(flagtype.StringSlice(),
            "tag", "add a tag (repeatable)")

        f.Var(flagtype.Enum("json", "yaml", "table"),
            "format", "output format")

        f.Var(flagtype.EnumDefault("sql", []string{"sql", "go"}),
            "type", "migration type")

        f.Var(flagtype.StringMap(),
            "label", "key=value (repeatable)")

        f.Var(flagtype.URL(),
            "endpoint", "API endpoint")

        f.Var(flagtype.Regexp(),
            "match", "filter pattern")
    }),
    Exec: func(ctx context.Context, state *cli.State) error {
        tags     := cli.GetFlag[[]string](state, "tag")
        format   := cli.GetFlag[string](state, "format")
        migType  := cli.GetFlag[string](state, "type")
        labels   := cli.GetFlag[map[string]string](state, "label")
        endpoint := cli.GetFlag[*url.URL](state, "endpoint")
        re       := cli.GetFlag[*regexp.Regexp](state, "match")

        _, _, _, _, _, _ = tags, format, migType, labels, endpoint, re
        return nil
    },
}

$ fetch --help
Usage:
  fetch [flags]

Flags:
  --endpoint url       API endpoint
  --format enum        output format
  --label stringMap    key=value (repeatable)
  --match regexp       filter pattern
  --tag stringSlice    add a tag (repeatable)
  --type enum          migration type (default: sql)

Each flagtype carries a type hint that shows up in the auto-generated help. Repeatable flags (StringSlice, StringMap) collect values across multiple appearances on the command line:

fetch --tag a --tag b --label env=prod --label tier=api