https://github.com/motemen/go-typeswitch-gen

Expands type switches with type variables to achieve generic functions in Golang
https://github.com/motemen/go-typeswitch-gen

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Expands type switches with type variables to achieve generic functions in Golang

• Host: GitHub
• URL: https://github.com/motemen/go-typeswitch-gen
• Owner: motemen
• Created: 2014-12-22T15:55:00.000Z (about 10 years ago)
• Default Branch: master
• Last Pushed: 2016-01-04T08:15:42.000Z (about 9 years ago)
• Last Synced: 2024-05-01T23:31:07.606Z (9 months ago)
• Language: Go
• Homepage:
• Size: 62.5 KB
• Stars: 34
• Watchers: 6
• Forks: 3
• Open Issues: 0
• Metadata Files:
  • Readme: README.adoc

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README

        
= go-typeswitch-gen

== INSTALLATION

  go get github.com/motemen/go-typeswitch-gen/cmd/tsgen

== USAGE

  tsgen [-w] [-main ] [-verbose]  

  Modes:

    expand:   expand generic case clauses in type switch statements by its actual arguments

    scaffold: generate stub case clauses based on types that implement subject interface

    sort:     sort case clauses in type switch statements

  Flags:

    -main="": entrypoint package

    -verbose=false: log verbose

    -w=false: write result to (source) file instead of stdout

== DESCRIPTION

`tsgen` is a toolbox for type switch statements in Go. Basically it does code generation to help coding with type switches. Currently it supports three functions: expand, sort and scaffold. **expand** generates new case clause from template clause with type placeholders, achieving type generic codes. **scaffold** fills type switches with stub case clauses. **sort** sorts case clauses in type switches.

In any mode `-w` option will rewrite the file itself, otherwise prints out to stdout.

== TEMPLATE EXPANSION: USING TEMPLATE VARIABLES

[source,go]

----

// example.go

type T interface{} // treated as a type variable

func onGenericStringMap(m interface{}) {

    switch m := m.(type) {

    case map[string]T:

        var x T

        ...

    }

}

----

And in somewhere:

[source,go]

----

// main.go

func main() {

    onGenericStringMap(map[string]bool{})

    onGenericStringMap(map[string]io.Reader{})

}

----

And run:

  tsgen example.go

Then you will get type switch clauses whose type variables are replaced with concrete types:

[source,go]

----

func onGenericStringMap(m interface{}) []string {

    switch m := m.(type) {

    case map[string]bool:

        var x bool

        ...

    case map[string]io.Reader:

        var x io.Reader

        ...

    case map[string]T:

        var x T

        ...

    }

}

----

== TEMPLATE EXPANSION: DESCRIPTION

`tsgen expand` rewrites type switch statements which has template case clauses, which are case clauses with type variables in their case expression (e.g. `case map[string]T:` or `case chan S1:`). `tsgen` analyzes the source code and detects the actual argument types (e.g. `map[string]io.Reader` or `chan bool`), then generates new case clauses with concrete types based on the templates and adds them to the parent type switch statement.

Types with names of uppercase letters and numbers are considered as type variables.

== USAGE WITH `go generate`

Add lines below to expand type switches with `go generate`:

[source,go]

----

//go:generate tsgen -w expand $GOFILE

//go:generate goimports -w $GOFILE

----

For a complete example, consult the `_example` directory.

== AUTHOR

motemen