Add the ability to run custom rules included in a project

docs/configuration.rst

@@ -15,6 +15,7 @@ If ``-c`` is not provided, yamllint will look for a configuration file in the
 following locations (by order of preference):
 
 - ``.yamllint`` in the current working directory
+- ``.yamllint/config`` in the current working directory
 - ``$XDG_CONFIG_HOME/yamllint/config``
 - ``~/.config/yamllint/config``
 

docs/custom_rules.rst

@@ -0,0 +1,62 @@
+Custom Rules
+============
+
+There are times when you might like to add custom rules to your
+project.  This could be because the rules you'd like to enforce are
+not general enough to consider including in upstream yamllint.
+
+yamllint will look for custom rules in ``.yamllint/rules``.  To enable
+a custom rule you need to explicitly reference the rule in your
+config.
+
+Example
+~~~~~~~
+
+In this example there is a custom rule called ``truthy`` that will
+complain if ambiguous truthy values are not quoted.
+
+This is the directory structure:
+
+.. code:: plain
+
+   .
+   |-- .yamllint
+   |   |-- config
+   |   `-- rules
+   |       |-- __init__.py
+   |       `-- truthy.py
+   `-- example.yml
+
+   2 directories, 4 files
+
+This is an example yaml file with ambiguous truthy values:
+
+.. code:: yaml
+
+   ---
+   a: y
+   b: yes
+   c: on
+   d: True
+
+This is an example config file:
+
+.. code:: yaml
+
+   ---
+   extends: default
+
+   rules:
+     truthy: enable
+
+Lint problems from the custom rule are now included in the yamllint
+output:
+
+.. code:: plain
+
+   $ yamllint example.yml
+   example.yml
+     2:3       error    ambiguous truthy value is not quoted  (truthy)
+     3:3       error    ambiguous truthy value is not quoted  (truthy)
+     4:3       error    ambiguous truthy value is not quoted  (truthy)
+     5:3       error    ambiguous truthy value is not quoted  (truthy)

docs/index.rst

@@ -26,3 +26,4 @@ Table of contents
    disable_with_comments
    development
    text_editors
+   custom_rules

tests/rules/test_custom.py

@@ -0,0 +1,73 @@
+# -*- coding: utf-8 -*-
+# Copyright (C) 2016 Adrien Vergé
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import os
+import shutil
+import tempfile
+
+from tests.common import RuleTestCase
+from yamllint.config import YamlLintConfigError
+
+
+class CustomTestCase(RuleTestCase):
+    rule_id = 'custom'
+
+    @classmethod
+    def setUpClass(self):
+        self.tmpd = tempfile.mkdtemp()
+        rules = os.path.join(self.tmpd, '.yamllint', 'rules')
+        os.makedirs(rules)
+
+        with open(os.path.join(rules, '__init__.py'), 'w'):
+            pass
+
+        with open(os.path.join(rules, 'custom.py'), 'w') as f:
+            f.write("""ID = 'custom'
+TYPE = 'token'
+
+def check(*args, **kwargs):
+    if 0:
+        yield
+""")
+
+        self.orig_cwd = os.getcwd()
+        os.chdir(self.tmpd)
+
+    def test_disabled(self):
+        conf = 'custom: disable\n'
+
+        self.check('---\n', conf)
+
+    def test_enabled(self):
+        conf = 'custom: enable\n'
+
+        self.check('---\n', conf)
+
+    def test_config_present(self):
+        conf = 'custom: enable\n'
+
+        self.check('---\n', conf)
+
+    def test_config_missing(self):
+        conf = ''
+
+        with self.assertRaises(YamlLintConfigError):
+            self.check('---\n', conf)
+
+    @classmethod
+    def tearDownClass(self):
+        os.chdir(self.orig_cwd)
+        shutil.rmtree(self.tmpd)

yamllint/cli.py

@@ -113,6 +113,8 @@ def run(argv=None):
             conf = YamlLintConfig(file=args.config_file)
         elif os.path.isfile('.yamllint'):
             conf = YamlLintConfig(file='.yamllint')
+        elif os.path.isfile('.yamllint/config'):
+            conf = YamlLintConfig(file='.yamllint/config')
         elif os.path.isfile(user_global_config):
             conf = YamlLintConfig(file=user_global_config)
         else:

yamllint/rules/__init__.py

@@ -14,6 +14,10 @@
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
+import importlib
+import os
+import sys
+
 from yamllint.rules import (
     braces,
     brackets,
@@ -54,6 +58,15 @@ _RULES = {
 
 
 def get(id):
+    if id not in _RULES:
+        try:
+            if os.path.isdir('.yamllint'):
+                sys.path.append('.yamllint')
+            module = importlib.import_module('rules.' + id)
+            _RULES[module.ID] = module
+        except ImportError as exc:
+            pass
+
     if id not in _RULES:
         raise ValueError('no such rule: "%s"' % id)