doc.go

// Copyright 2014 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.

// Stringer is a tool to automate the creation of methods that satisfy the fmt.Stringer
// interface. Given the name of a (signed or unsigned) integer type T that has constants
// defined, stringer will create a new self-contained Go source file implementing
//
//	func (t T) String() string
//
// The file is created in the same package and directory as the package that defines T.
// It has helpful defaults designed for use with go generate.
//
// Stringer works best with constants that are consecutive values such as created using iota,
// but creates good code regardless. In the future it might also provide custom support for
// constant sets that are bit patterns.
//
// For example, given this snippet,
//
//	package painkiller
//
//	type Pill int
//
//	const (
//		Placebo Pill = iota
//		Aspirin
//		Ibuprofen
//		Paracetamol
//		Acetaminophen = Paracetamol
//	)
//
// running this command
//
//	stringer -type=Pill
//
// in the same directory will create the file pill_string.go, in package painkiller,
// containing a definition of
//
//	func (Pill) String() string
//
// That method will translate the value of a Pill constant to the string representation
// of the respective constant name, so that the call fmt.Print(painkiller.Aspirin) will
// print the string "Aspirin".
//
// Typically this process would be run using go generate, like this:
//
//	//go:generate stringer -type=Pill
//
// If multiple constants have the same value, the lexically first matching name will
// be used (in the example, Acetaminophen will print as "Paracetamol").
//
// With no arguments, it processes the package in the current directory.
// Otherwise, the arguments must name a single directory holding a Go package
// or a set of Go source files that represent a single Go package.
//
// The -type flag accepts a comma-separated list of types so a single run can
// generate methods for multiple types. The default output file is t_string.go,
// where t is the lower-cased name of the first type listed. It can be overridden
// with the -output flag.
//
// Types can also be declared in tests, in which case type declarations in the
// non-test package or its test variant are preferred over types defined in the
// package with suffix "_test".
// The default output file for type declarations in tests is t_string_test.go with t picked as above.
//
// The -linecomment flag tells stringer to generate the text of any line comment, trimmed
// of leading spaces, instead of the constant name. For instance, if the constants above had a
// Pill prefix, one could write
//
//	PillAspirin // Aspirin
//
// to suppress it in the output.
package main // import "golang.org/x/tools/cmd/stringer"