package flagbind

Package flagbind parses the exported fields of a struct and binds them to flags in a flag.FlagSet or pflag.FlagSet.

Bind allows for creating flags declaratively right alongside the definition of their containing struct. For example, the following stuct could be passed to Bind to populate a flag.FlagSet or pflag.FlagSet.

flags := struct {
        StringFlag string `flag:"flag-name;default value;Usage for string-flag"`
        Int        int    `flag:"integer;5"`

        // Flag names default to `auto-kebab-case`
        AutoKebabCase int

        // If pflag is used, -s is be used as the shorthand flag name,
        // otherwise it is ignored for use with the standard flag package.
        ShortName bool `flag:"short,s"`

        // Optionally extende the usage tag with subsequent `use` tags
        // on _ fields.
        URL string `flag:"url,u;http://www.example.com/;Start usage here"
        _   struct{} `use:"continue longer usage string for --url below it",

        // Nested and Embedded structs can add a flag name prefix, or not.
        Nested     StructA
        NestedFlat StructB           `flag:";;;flatten"`
        StructA                      // Flat by default
        StructB    `flag:"embedded"` // Add prefix to nested field flag names.

        // Ignored
        ExplicitlyIgnored bool `flag:"-"`
        unexported        bool
}{
        // Default values may also be set directly to override the tag.
        StringFlag: "override default",
        _URL: "Include a longer usage string for --url here",
}

fs := pflag.NewFlagSet("", pflag.ContinueOnError)
flagbind.Bind(fs, &flags)
fs.Parse([]string{"--auto-kebab-case"})

Bind works seemlessly with both the standard library flag package and the popular [github.com/spf13/pflag](https://github.com/spf13/pflag) package.

If pflag is used, for types that implement flag.Value but not pflag.Value, Bind wraps them in an adapter so that they can still be used as a pflag.Value. The return value of the additional function Type() string is the type name of the struct field.

Additional options may be set for each flag. See Bind for the full documentation details.