Tabtab

Rebar3 plugin - autocompletion generator for rebar3.

Drawbacks of current completion files

1. There is no completion for rebar3 plugins! (nor providers, nor their flags)
2. There is no completion for rebar3 templates! (nor template name, nor variables!)
3. There is no completion for rebar3 aliases defined in rebar.config
4. There is no completion for profiles when performing rebar3 as
5. Whenever autocompleting flags, after you type the first flag, completion is gone!
6. There is no completion for tasks when performing rebar3 do
7. Current rebar3 is static and handwritten - each update to providers may demand update in autocomplete files (update for each shell type!).
8. No support for rebar3 aliases. You wan't your autocompletion to trigger on r3 or rebar? You need to modify the autocompletion file yourself :D
9. No type hints for arguments
10. Limited nesting support - you cant have a task that has tasks, etc.
    • also only 1 previous word can be seen which could also cause collisions in nested commands!

There actually exist an issue from one of the rebar3 maintainers so I guess this will be welcome, although the issue doesn't mention autocompleting plugins/templates and other stuff. I believe that, if proven useful, this may become integrated into rebar3.

Goal

Create a rebar3 plugin that generates an completion file based on the current configuration of the project. This can lead to different completions in different shell sessions, so basic mechanism for integration should also be supported. Without good autocomplete it's hard to use tools that have a lot of (nested) commands (e.g. rebar3_hex plugin) - like programming without LSP.

Non-goals (currently)

• Efficiency - I've abused lists:concat/1 and strings a lot!
• Error handling - It's very minimal currently
• Testing

Features

• Dynamically generated providers autocomplete
• Autocomplete for plugin providers and their args
• Autocomplete for templates and their variables
• Preserve autocomplete after first flag/arg
• Autocomplete for rebar3 aliases defined in rebar.config
• Autocomplete profile when running rebar3 as
• Autocomplete tasks when running rebar3 do
• Unlimited command nesting supported!
  • Ready to support argparse one day!
• Autodetect shell type
• Automatic integration
  • Probably doable via rebar hooks, but that requires this provider to become hookable!
• Type hints
• Support for OS-level aliases
  • Out-of-the-box only in bash,
  • For zsh read this.

Demo

Prerequisites:

• some Unix/MacOS (tested on Ubuntu 20.04 with both shells)
• bash or zsh shell (tested on bash 5.0.17 and zsh 5.8)
• rebar3 (tested on 3.22.0)
• erlang version >= 25.0 (tested on 26.1.2)

Steps:

1. Include tabtab in project_plugins in rebar3.config

   • 1. method (recommended if you want to modify something in the program)

     1. Clone tabtab
     2. cd to some rebar3 project and run the following:

     mkdir -p _checkouts
     ln -s $PATH_TO_TABTAB_DIR _checkouts/tabtab 

     3. Put {project_plugins, [tabtab]} in rebar.config

   • 2. method

     • Put {project_plugins, [{tabtab, {git, "https://github.com/spawnfest/tabtab.git", {branch, "master"}}}]} in rebar.config
2. Run rebar3 compile or rebar3 plugins list to compile tabtab plugin
3. Run rebar3 tabtab to generate a completion file
   • shell type is autodetected via $SHELL variable, but you can specify it via -s flag
   • By default, completion file is named _rebar3 and is located in _build/<profile>/
     • You can override this with file config value
4. Integrate the completion file
   • bash
     • run source <(cat $PATH_TO_COMPLETION_FILE)
   • zsh
     • If first time doing zsh autocompletion, read this
     • run eval "$(cat $PATH_TO_COMPLETION_FILE)"; compdef _rebar3 rebar3
       • or source ~/.zshrc (if your file is somewhere in $fpath)
5. Enjoy not trying to remember all plugin commands and flags :D

Future work

• Automatic integration of completion files
• Support more shells types
• Finish listed features
• Style improvements
• Error handling
• Utilize tabtab to generate autocompletion for escripts

Extras

Configuration and options

Configuration is in rebar.config and options are passed in CLI when running rebar3 tabtab.

Configuration:

    {tabtab, [{file,file:filename_all()},
              {aliases, [string()]}]}

• file - absolute or relative (to _build/<profile/)
  • target directory will be created if missing
• aliases - list of strings on which you want to trigger autocomplete, e.g. ["r3", "rebar"]

Options:

Short	Long	Value	Default
-s	--shell	bash or zsh	autodetected (bash if detection fails)
-h	--hints	boolean	true
-t	--type_hints	boolean	false

Implementation

• Implement it as plugin or as part of rebar3?
  • I decided to go with the plugin because I can develop it on my own if rebar3 maintainers decide not to include it in rebar3. Also, it should be easy to convert plugin to core components, but not the other way around.
• Core part must support both argparse and getopt argument specification
  • Reason 1: rebar3 may switch to argparse somewhere in the future
  • Reason 2: Core part could be used to autocomplete escripts.

ZSH tutorial

I've had some troubles with zsh autocompletion because I've done it first time, so here are steps to save you some time:

1. Install zsh
2. Create .zshrc file in your $HOME directory and add the following:

   •  fpath=( $DIR_WHERE_YOU_STORE_COMPL_FILES "${fpath[@]}" )
     
      autoload -U compinit; compinit

! With zsh it is important that the completion file is named exactly as completion function it introduces! (_rebar3 in this case)

ZSH trigger autocomplete on alias

For alias e.g. r3 you need file _r3 somewhere in your fpath with the following contents:

#compdef _r3 r3

function _r3 {
    _rebar3
}   

and then load that file the same way as the original completion file.

Inspo

Got inspired by 1Password completion generation. Instructions for integrations are also mostly theirs.

Contact

marko.mindek@gmail.com

Note: whole plugin was entirely developed during Spawnfest.