impl

impl and goimpl are a library and a tool to generate method stubs for implementing interfaces in golang (IDE type functionality).

You type

sort.Interface ml *musicList

and it transforms it to

func (ml *musicList) Len() int {
	panic("TODO: implement this method")
}

func (ml *musicList) Less(i int, j int) bool {
	panic("TODO: implement this method")
}

func (ml *musicList) Swap(i int, j int) {
	panic("TODO: implement this method")
}

It can do this for any packages (not only core libraries, but for any code you use/write).

How To Specify The Interface?

The tests have many examples. In short, the path is expected to be in the format of <package>.<interface>, where <package> is exactly as you have to specify it in an import statement. Here are a few examples:

io.Reader
sort.Interface
// Assuming you've written a package you import 
// with "impl/impl/test_data/panther"
impl/impl/test_data/panther.Clawable
// Assuming you've imported package "github.com/the/package/path"
// which has interface "Interface"
github.com/the/package/path.Interface

Optionally, you could specify only 1 method to scaffold:

sort.Interface::Len

How to Setup?

With Your Favorite Editor

Since gomipl is a command line tool that works well with go generate, it can easily integrate with any editor or IDE. Follow the steps below:

1. Get the CLI tool goimpl by running the following go command in your terminal

   go get -u github.com/ajmesa9891/impl/goimpl

2. Have your editor run go generate on file save. If you're using Sublime with GoSublime:

   • Open GoSublime user settings (Preferences > Package Settings > GoSublime > User Settings).

   • Modify your "on_save" option to something similar to

     "on_save": [
           {"cmd": "gs9o_open", "args": {"run": ["go", "generate"], "focus_view": false}}
     ],
     

   • Save the user settings.

3. Add //go:generate goimpl $GOFILE as a snippet. If you're using Sublime with GoSublime:

   • Open GoSublime user settings (Preferences > Package Settings > GoSublime > User Settings).

   • Modify your "snippets" option to something similar to

     "snippets": [
        {
           "match": {"global": true},
           "snippets": [
              {
                 "text": "goimpl",
                 "title": "go generate impl",
                 "value": "//go:generate goimpl \\$GOFILE $0"
              }
           ]
        }
     ],
     

4. Run your snippet, add the interface you're trying to implement and the receiver, save your file, and see the interface scaffolding implemented. If you're using GoSublime press Esc to exit the gs9o terminal. For example, try

   //go:generate goimpl $GOFILE sort.Interface ml *musicList

   Save and the comment should have transformed into the interface scaffolding.

With Anything Else

Essentially, goimpl takes a file, an interface, and a receiver, and replaces a comment with the implementation of that interface. The go generate tool allows us to easily integrate it into the golang ecosystem. Try using the tool with go generate alone to understand how to integrate it with anything else.

Why 2? impl & goimpl?

impl is a library to create interface stubs and can only be used programmatically. goimpl is a command layered on top that makes it easy to use with go generate.