Completion library for words, commands, and sentences

npm install completion
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Completion library for words, commands, and sentences

This was built as part of foundry, a CLI utility for making releases painless.

$ git chec|
$ git checkout |

$ git checkout dev/|
dev/ dev/goodbye.moon

$ git chec|dev/
$ git checkout |dev/

Getting Started

Install the module with: npm install completion

var Completion = require('completion');
var completion = new Completion({
  git: {
    checkout: function (info, cb) {
      // For `git checkout dev/|`
      // info.words.value = ['git', 'checkout', 'dev/']
      // info.word.partialLeft = 'dev/'
      getGitBranches(function (err, allBranches) {
        if (err) {
          return cb(err);

        var partialLeftWord = info.word.partialLeft;
        var branches = allBranches.filter(function (branch) {
          // 'chec' === 'chec' (from 'checkout')
          return partialLeftWord === branch.substr(0, partialLeftWord.length);
        cb(null, branches);
  // `git chec|`
  line: 'git chec',
  cursor: 8
}, function (err, results) {
  results; // ['checkout']

How it works

In bash, tab completion will override the the left half of the current word.

As a result, for cases like:

$ git chec|
$ git checkout| # requires ['checkout'] to be returned

Unfortunately, while we can deal with commands, we cannot predict the values of those.

You will still be responsible for handling of right partials in the autocompleted items.

$ git checkout a|c
  'abc', # `git checkout abc` - Checkout `abc` branch
  'aaa' # `git checkout aaa c` - Chekckout `c` file from `aaa` branch


completion exposes the Completion constructor via its module.exports

new Completion(tree)

Create a new completion instance

  • tree Object - Outline of program
    • Each key represents a new command (e.g. git, checkout)
    • Each value can be
      • An object representing another layer of commands
      • A function that will callback with potential matches
        • The function should be error-first; have a signature of function (info, cb)
        • info Object - Collection of distilled information
        • cb Function - Error-first callback function to run with matches
          • cb has a signature of function (err, results)
      • null representing a terminal function which has no further predictive input
        • If you want to list out files, do so. Don't use null for that case.

completion.complete(params, cb)

Get potential completion matches

  • params Object - Information similar to that passed in by bash's tab completion
    • line String - Input to complete against (similar to COMP_LINE)
    • cursor Number - Index within line of the cursor (similar to COMP_POINT)
  • cb Function - Error-first callback function that receives matches
    • cb should have a signature of function (err, results)


An example of git would be

var gitCompletion = new Completion({
  git: {
    // `git checkout master`
    checkout: function (info, cb) {
      // Get git branches and find matches
    remote: {
      // `git remote add origin`
      add: null, // No possible tab completion here
      // `git remote rm origin`
      rm: function (info, cb) {
        // Get git branches and find matches

  // `git remo|add`
  line: 'git remoadd',
  cursor: 8
}, function (err, results) {
  results; // ['remote']

  // `git remote |`
  line: 'git remote',
  cursor: 11
}, function (err, results) {
  results; // ['add', 'remove']


In lieu of a formal styleguide, take care to maintain the existing coding style. Add unit tests for any new or changed functionality. Lint via grunt and test via npm test.


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As of Dec 15 2013, Todd Wolfson has released this repository and its contents to the public domain.

It has been released under the UNLICENSE.

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