flagset

Package flagset provides an opinionated approach to constructing an applications' configuration using Golang structs and tags. It's designed in a way that allows configuration to be loaded from files, environment variables, and/or command line flags. The following details the various tags that can be specified on a primitive field.

• json - string - Configure the name of the flag. Convention is to use snake case.

• usage - string - Configure the description string of the flag.

• default - any - Configure the default value for the flag. Can be overridden by setting the value on the struct.

• hidden - bool - Hides the flag from output. The value can still be configured.

• required - bool - Specifies that the flag must be specified.

Nested structures are supported, making application configuration composable and portable between systems.

import go.pitz.tech/lib/flagset

Usage

func ExampleString

func ExampleString(examples ...string) string

ExampleString formats a list of examples so that they display properly in the terminal. This function just pulls things out into a simple helper.

type Extractor

type Extractor struct {
	Prefix    []string
	EnvPrefix []string
}

Extractor extracts flags from provided interfaces.

func (Extractor) Child

func (f Extractor) Child(name string) Extractor

Child creates a new Extractor and adds name to the end of the current Prefix.

func (Extractor) Clone

func (f Extractor) Clone() Extractor

Clone creates a copy of the current Extractor.

func (Extractor) Extract

func (f Extractor) Extract(v interface{}) FlagSet

Extract returns the set of flags associated with the provided structure.

type Filter

type Filter func(flag cli.Flag) bool

Filter allows the user to inspect the flag to determine if it should be in the resulting FlagSet.

type FlagSet

type FlagSet []cli.Flag

FlagSet provides additional functionality on top of a collection of flags.

func Extract

func Extract(v interface{}) FlagSet

Extract parses the provided object to create a flagset.

func ExtractPrefix

func ExtractPrefix(prefix string, v interface{}) FlagSet

ExtractPrefix parses the provided to create a flagset with the provided environment variable prefix.

func (FlagSet) Filter

func (flags FlagSet) Filter(allow Filter) FlagSet

Filter returns a new FlagSet that contains flags allowed by the provided Filter.

type Slice

type Slice[T any] []T

Slice provides a configuration file (YAML, JSON, TOML) friendly variant of the cli.StringSlice value. It also supports parsing JSON configuration from environment variables.

func (*Slice[T]) Set

func (s *Slice[T]) Set(value string) (err error)

Set appends the provided value to the underlying slice. If the value appears to be a JSON string, then we attempt to unmarshal the JSON before appending the resulting values to the underlying slice. Currently, this mechanism only supports primitive structures.

func (*Slice[T]) String

func (s *Slice[T]) String() string

String serializes the Slice as a json string.