Running Linters Locally

Using the Command Line

You can run all the various linters in the tree using the mach lint command. Simply pass in the directory or file you wish to lint (defaults to current working directory):

./mach lint path/to/files

Multiple paths are allowed:

./mach lint path/to/foo.js path/to/ path/to/dir

To force execution on a directory that would otherwise be excluded:

./mach lint -n path/in/the/exclude/list

Mozlint will automatically determine which types of files exist, and which linters need to be run against them. For example, if the directory contains both JavaScript and Python files then mozlint will automatically run both ESLint and Flake8 against those files respectively.

To restrict which linters are invoked manually, pass in -l/--linter:

./mach lint -l eslint path/to/files

You can see a list of the available linters by running:

./mach lint --list

Finally, mozlint can lint the files touched by outgoing revisions or the working directory using the -o/--outgoing and -w/--workdir arguments respectively. These work both with mercurial and git. In the case of --outgoing, the default remote repository the changes would be pushed to is used as the comparison. If desired, a remote can be specified manually. In git, you may only want to lint staged commits from the working directory, this can be accomplished with --workdir=staged. Examples:

./mach lint --workdir
./mach lint --workdir=staged
./mach lint --outgoing
./mach lint --outgoing origin/master
./mach lint -wo

Using a VCS Hook

There are also both pre-commit and pre-push version control hooks that work in either hg or git. To enable a pre-push hg hook, add the following to hgrc:

pre-push.lint = python:./tools/lint/

To enable a pre-commit hg hook, add the following to hgrc:

pretxncommit.lint = python:./tools/lint/

To enable a pre-push git hook, run the following command:

$ ln -s ../../tools/lint/ .git/hooks/pre-push

To enable a pre-commit git hook, run the following command:

$ ln -s ../../tools/lint/ .git/hooks/pre-commit

Note that the symlink will be interpreted as .git/hooks/../../tools/lint/

Automatically Fixing Lint Errors

Mozlint has a best-effort ability to fix lint errors:

$ ./mach lint --fix

Not all linters support fixing, and even the ones that do can not usually fix all types of errors. Any errors that cannot be automatically fixed, will be printed to stdout like normal. In that case, you can also fix errors manually:

$ ./mach lint --edit

This requires the $EDITOR environment variable be defined. For most editors, this will simply open each file containing errors one at a time. For vim (or neovim), this will populate the quickfix list with the errors.

The --fix and --edit arguments can be combined, in which case any errors that can be fixed automatically will be, and the rest will be opened with your $EDITOR.

Editor Integration


See details on how to set up your editor here

Editor integrations are highly recommended for linters, as they let you see errors in real time, and can help you fix issues before you compile or run tests.

Although mozilla-central does not currently have an integration available for ./mach lint, there are various integrations available for some of the major linting tools that we use: