susji / typestringer

typestringer is a program for generating Go code based on type names

typestringer

This program can be used to generate customizable code based on Go type names. One example would be the generation of String() functions to fulfill the Stringer interface.

Usage

$ typestringer -help

Several options exist for customizing the generated code. -include and -ignore may be used to define regular expressions for matching or not matching specific types. Diagnostic output is written to standard error and generated code by default to files located in the package paths. -stdout may be used to redirect the generated code to standard output.

As usual, typestringer may also be executed with go generate by including a comment such as the following somewhere in your code:

//go:generate typestringer

Installing

Builds for many platforms can be found here. You may also use the Go toolchain:

$ go install github.com/susji/typestringer@latest

Examples

The examples below use the typestringer code.

Basic

The type-specific format string is expanded with the type name passed two times so escaping other formatting directives must be done with %%:

$ typestringer \
      -stdout \
      -preamble 'import fmt' \
      -fmt 'func (t %s) String() string { return fmt.Sprintf("%s=%%v", t) }'

The generated code looks like this:

// Automatically generated by typestringer with the following parameters:
//   -stdout
//   -preamble
//   import fmt
//   -fmt
//   func (t %s) String() string { return fmt.Sprintf("%s=%%v", t) }
package main

import fmt

func (t stringsvar) String() string { return fmt.Sprintf("stringsvar=%v", t) }%

Chaining

If specific types should be treated differently and one generated file is desired, something like the following may be done:

$ { typestringer \
      -stdout \
      -preamble 'import fmt' \
      -include '^FIRST$' \
      -fmt 'func (t %s) String() string { return fmt.Sprintf("%s=%%v", t) }'$'\n' \
      ./generator/testdata/two;
    typestringer \
      -stdout \
      -no-package \
      -include '^SECOND$' \
      -fmt 'func (t %s) String() string { return "%s" }'$'\n' \
      ./generator/testdata/two;
  } 2>/dev/null

The generated code looks like this:

// Automatically generated by typestringer with the following parameters:
//   -stdout
//   -preamble
//   import fmt
//   -include
//   ^FIRST$
//   -fmt
//   func (t %s) String() string { return fmt.Sprintf("%s=%%v", t) }

//   ./generator/testdata/two
package two

import fmt

func (t FIRST) String() string { return fmt.Sprintf("FIRST=%v", t) }
// Automatically generated by typestringer with the following parameters:
//   -stdout
//   -no-package
//   -include
//   ^SECOND$
//   -fmt
//   func (t %s) String() string { return "%s" }

//   ./generator/testdata/two
func (t SECOND) String() string { return "SECOND" }