change: enable rules plugin support

enable rules plugin support and make yamllint loads plugin rules also,
along with simple test cases loading rules.

tests/test_rules.py

@@ -0,0 +1,48 @@
+# -*- coding: utf-8 -*-
+# Copyright (C) 2020 Satoru SATOH
+#
+# 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 unittest
+
+from tests.plugins import example
+
+import yamllint.rules
+
+
+RULE_NEVER_EXISTS = "rule_never_exists"
+PLUGIN_RULES = example.RULES_MAP
+
+
+class TestCase(unittest.TestCase):
+    """Test cases for yamllint.rules.__init__.*.
+    """
+    def test_get_default_rules(self):
+        self.assertEqual(yamllint.rules.get(yamllint.rules.braces.ID),
+                         yamllint.rules.braces)
+        self.assertEqual(yamllint.rules.get(yamllint.rules.braces.ID,
+                                            plugin_rules=PLUGIN_RULES),
+                         yamllint.rules.braces)
+        with self.assertRaises(ValueError):
+            yamllint.rules.get(RULE_NEVER_EXISTS)
+
+    def test_get_plugin_rules(self):
+        plugin_rule_id = example.override_comments.ID
+        plugin_rule_mod = example.override_comments
+
+        self.assertEqual(yamllint.rules.get(plugin_rule_id,
+                                            plugin_rules=PLUGIN_RULES),
+                         plugin_rule_mod)
+
+        with self.assertRaises(ValueError):
+            yamllint.rules.get(RULE_NEVER_EXISTS, plugin_rules=PLUGIN_RULES)

yamllint/rules/__init__.py

@@ -14,6 +14,7 @@
 # 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 yamllint.plugins
 from yamllint.rules import (
     braces,
     brackets,
@@ -62,9 +63,20 @@
     truthy.ID: truthy,
 }
 
+_PLUGIN_RULES = yamllint.plugins.get_plugin_rules_map()
 
-def get(id):
-    if id not in _RULES:
-        raise ValueError('no such rule: "%s"' % id)
 
-    return _RULES[id]
+def get(rule_id, rules=None, plugin_rules=None):
+    if rules is None:
+        rules = _RULES
+
+    if plugin_rules is None:
+        plugin_rules = _PLUGIN_RULES
+
+    if rule_id in rules:
+        return rules[rule_id]
+
+    if rule_id in plugin_rules:
+        return plugin_rules[rule_id]
+
+    raise ValueError('no such rule: "%s"' % rule_id)