Local Golang playground

The simple mode for GNU/Emacs for setting up local Go language playground with features similar (and with help of go-mode even outperform!) service at play.golang.org. You may treat it like the simple REPL for Go. This is not a wrapper for working with play.golang.org from Emacs (it is already did by original go-mode), this is complete alternative for setting local playground inside Emacs without using browser for experiments with code snippets.

Web playground at play.golang.org is a nice idea. It has not require setup and it executes your code in a restricted environment where you can't damage you system. But it brings many restrictions too especially when you want use additional helpers for working with your code: formatters, code completers etc. Emacs offers many such tools for Go development so it is the most comfortable play with snippets inside Emacs instead of rude webeditor. Of course local playground requres you to setup Go environment but if you developing in Go (or you want to do it) you are anyway would need to setup go-mode and helper tools for working with code in a comfortable way.

Features

• it works under go-mode with all you plugins installed (like autocompletion, linters and so on)
• the playground files saved in the subdirectory under GOPATH that helps you keep library of useful snippets
• it could split the code into arbitrary number of files
• it could import any external packages from your GOPATH
• uses vendored packages in your snippet dir
• could be used with modules with the latest Go versions

Install

Firstly install go-mode and gotest — these are mandatory. Setup any additional tools you want for Golang (see Emacs Wiki for guides or google for "emacs+golang"). Personally I recommend use goimports for automatically add import clauses to your snippets. Because usually when you test some ideas you want get working code as fast as possible. And goimports helps with it.

Install go-playground from MELPA:

M-x package-install RET go-playground

If you want share snippets use go-play-buffer from go-mode. Install gist-buffer from MELPA if you want publish gists on github.com.

The mirror repository of the project: https://notabug.org/grafov/go-playground. I really not think that this small project need the mirror but I just would like advertise a nice git hosting for FOSS. Try notabug.org for your projects! :)

Usage

Quick start

1. From any mode run M-x go-playground for start a new playground buffer filled with basic template for main package (see the picture below).
2. Add your code then press Ctl-Return (it bound to go-playground-exec command). It will save, compile and exec the snippet code.
3. When you played enough with this snippet just run M-x go-playground-rm. It will remove the current snippet with its directory and all files.

Mode not offers default bindings except Ctl-Return. It just lefts the space for you.

For easy running the template declares main package with defined main() function. Each snippet saved to its own directory (named by timestamp by default). Remember go-playground runs the compiler as go run *.go so any sources from the snippet directory will be included.

List of interactive functions

Function name	Description
go-playground	Create a new playground buffer with basic template for the main package.
go-playground-download	Download the snippet from the URL at play.golang.org.
go-playground-exec	Save, compile and run the code of the snippet.
go-playground-cmd	Save the code then prompts for the command (compile-mode used).
go-playground-upload	Upload the buffer to play.golang.org and return the short URL.
go-playground-rm	Remove the snippet with its directory with all files.

List of customizable variables

Function name	Description
go-playground-ask-filename	Ask for the snippet filename on a new playground creation. By default it got name snippet.go.
go-playground-basedir	Default directory where snippets dirs will placed. Each new snippet got a new dir under this. It has sense place the default directory under GOPATH. Var introduced in the release 1.1.
go-playground-confirm-deletion	Ask for confirmation before snippet deletion. It may be annoying so you can switch confirmations off. Var introduced in the release 1.2.
go-playground-go-command	Set a custom path to go command, possibly with environment (example: "CGO_ENABLED=0 /opt/bin/go").
go-playground-init-command	Setup shell command that will be run once when a new snippet just created.
go-playground-compiler-args	That arguments should be passed for the compiler.

Example screen after creation of a new snippet:

Using with go modules

By default the playground runs go-command as it defined in settings of go-mode. You could use special customized compiler path with go-playground-go-command. For using with modules it could be used such way:

1. Set go-playground-go-command to "GO111MODULE=on".
2. Set go-playground-init-command to "go mod init".

Using with lsp-mode

If you use lsp-mode, you can add a hook in your init file to cleanup the workspace when a snippet is removed, for example:

(defun my/go-playground-remove-lsp-workspace () (when-let ((root (lsp-workspace-root))) (lsp-workspace-folders-remove root)))
(add-hook 'go-playground-pre-rm-hook #'my/go-playground-remove-lsp-workspace)

Similar projects

• Try go-scratch it even simplier than go-playground. But it prevents you from using many of tools because it not keeps code in files.
• gorepl-mode is REPL for Go, helpful for interactive research of code.

Licence

Under terms of GPL v3. See LICENSE file.

Future plans and accepting contributions

I don't want to make this package much complex. Most of go-playground functions depends on other packages around go-mode. And it is good way. But one thing I want to add is snippet list buffer where you can easily find and edit/delete snippets of your library. Bugfixes and small features accepted as well.