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
- works under go-mode with all your plugins (like lsp, linters and so on)
- keeps the library of snippets under a customized root path
- allows split the code into arbitrary number of files
- allows add new subdirs with subpackages
- import any external packages
- compatible with Go modules but could be customized for old GOPATH way
Install
First 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"). Minimal way is install goimports that automatically add import clauses to your snippets. For a fully functional Go IDE look at lsp and supplementary packages.
Install go-playground from MELPA:
M-x package-install RET go-playground
Or:
(use-package go-playground)
If you want to 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
- From any mode run
M-x go-playgroundfor start a new playground buffer filled with basic template formainpackage (see the picture below). - Add your code then press
Ctl-Return(it bound togo-playground-execcommand). It will save, compile and exec the snippet code. - 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:
- Set
go-playground-go-commandto "GO111MODULE=on". - Set
go-playground-init-commandto "go mod init".
Snippet with multiple files and subpackages
Explained here #19.
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.