Writing a coala Configuration File (coafile and coarc)

This document gives a short introduction to the specification of a coala configuration file. It is meant to be rather factual. If you wish to learn by example, please take a look at Getting Started with coala. It also teaches how to change settings inside a coala file to suit your taste.

Naming, Scope and Location

You can use up to three coafiles to configure your project.

  1. A project-wide coafile.
  2. A user-wide coafile.
  3. A system-wide coafile.

Project-Wide coafile

It is a convention that the project-wide coafile is named .coafile and lies in the project root directory. If you follow this convention, simply executing coala from the project root will execute the configuration specified in that file.

Settings given in the project-wide coafile override all settings given by other files and can only be overridden by settings given via the command line interface.

User-Wide and System-Wide coafile

You can place a .coarc file in your home directory to set certain user wide settings. Those settings will automatically be taken for all projects executed with that user.

All settings specified here override only settings given by the system wide coafile which has the lowest priority. The default_coafile must lie in the coala installation directory and is valid for everyone using this coala installation.

It can be used to define the type of files you usually don’t want to lint, like minified files (e.g. *.min.js) and backup files (e.g. *.orig):

ignore = **.min.js, **.orig

Explicit Setting Inheritance

Every coafile contains one or more sections. Section names are case insensitive. The old(pre 0.11.x) implicit section inheritance syntax has been deprecated and has been scheduled for removal in coala version 0.12.0. Instead, define section inheritance explicitly by naming a section in the format [basesection.newsection]. Extra values can be appended to an inherited setting using the += operator.

Consider the following coafile:

enabled = True
overridable = 2
ignore = vendor1/

overridable = 3
ignore += vendor2/
other = some_value

overridable = 4
ignore += vendor3/
other = some_other_value

This is the same file without section inheritance:

enabled = True
overridable = 2
ignore = vendor1/

enabled = True
overridable = 3
ignore = vendor1/, vendor2/
other = some_value

enabled = True
overridable = 4
ignore = vendor1/, vendor3/
other = some_other_value

All settings must be part of a section, so don’t do this for implicit inheritance (this is also deprecated behavior). Implicit inheritance was leading to a section automatically getting inherited to all other sections without semantically making sense.

# bad! setting1 = 1

[section1] # setting1 is inherited setting2 = 2

Instead, make the inheritance explicit:

# better!
setting1 = 1

# setting1 is inherited
setting2 = 2

Defining Aspects and Tastes

Aspects is an alternative way to configure coala. In this mode, we don’t need to explicitly state list of bears, coala will choose it automatically based on requested aspects in coafile. To run coala in this mode, we need to define aspects, files, languages, and optionally aspect tastes setting. See the following example:

files = **
aspects = aspectname1, AspectName2 # case-insensitive
# defining an aspect's taste
aspectname1:aspect_taste = 80
# we can define subaspect taste through its parent
aspectname1:subaspect_taste = word1, word2, word3

files = **.py
language = Python
# appending additional aspect
aspects += aspectname3
# excluding certain subaspect
excludes = AspectName2Subaspect

Comments, Escaping and Multiline Values and Keys

Comments are simply done with a preceding #. If you want to use a # within a value, you can simply escape it:

a_key = a\#value # And a comment at the end!

Any line not containing an unescaped = is simply appended to the value of the last key:

a_key = a
# this is not part of the value
that /= is
very long!

Similarly, you can also set a value to multiple keys: key_1, key_2 = value is equivalent to key_1 = value and key_2 = value in separate lines.

As the backslash is the escape character it is recommended to use forward slashes as path separator even on Windows (to keep relative paths platform independent), use double-backslashes if you really mean a backslash in all places.

You can now proceed to an example with Getting Started with coala.