New rule key-ordering

closes #67

docs/rules.rst

@@ -74,6 +74,11 @@ key-duplicates
 
 .. automodule:: yamllint.rules.key_duplicates
 
+key-ordering
+--------------
+
+.. automodule:: yamllint.rules.key_ordering
+
 line-length
 -----------
 

tests/rules/test_key_ordering.py

@@ -0,0 +1,67 @@
+# -*- coding: utf-8 -*-
+# Copyright (C) 2017 Johannes F. Knauf
+#
+# 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/>.
+
+from tests.common import RuleTestCase
+
+
+class KeyOrderingTestCase(RuleTestCase):
+    rule_id = 'key-ordering'
+
+    def test_disabled(self):
+        conf = 'key-ordering: disable'
+        self.check('---\n'
+                   'block mapping:\n'
+                   '  secondkey: a\n'
+                   '  firstkey: b\n', conf)
+        self.check('---\n'
+                   'flow mapping:\n'
+                   '  {secondkey: a, firstkey: b}\n', conf)
+        self.check('---\n'
+                   'second: before_first\n'
+                   'at: root\n', conf)
+        self.check('---\n'
+                   'nested but OK:\n'
+                   '  second: {first: 1}\n'
+                   '  third:\n'
+                   '    second: 2\n', conf)
+
+    def test_enabled(self):
+        conf = 'key-ordering: enable'
+        self.check('---\n'
+                   'block mapping:\n'
+                   '  secondkey: a\n'
+                   '  firstkey: b\n', conf,
+                   problem=(4, 3))
+        self.check('---\n'
+                   'flow mapping:\n'
+                   '  {secondkey: a, firstkey: b}\n', conf,
+                   problem=(3, 18))
+        self.check('---\n'
+                   'second: before_first\n'
+                   'at: root\n', conf,
+                   problem=(3, 1))
+        self.check('---\n'
+                   'nested but OK:\n'
+                   '  second: {first: 1}\n'
+                   '  third:\n'
+                   '    second: 2\n', conf)
+
+    def test_key_tokens_in_flow_sequences(self):
+        conf = 'key-ordering: enable'
+        self.check('---\n'
+                   '[\n'
+                   '  key: value, mappings, in, flow: sequence\n'
+                   ']\n', conf)

yamllint/conf/default.yaml

@@ -39,6 +39,7 @@ rules:
     indent-sequences: true
     check-multi-line-strings: false
   key-duplicates: enable
+  key-ordering: disable
   line-length:
     max: 80
     allow-non-breakable-words: true

yamllint/rules/__init__.py

@@ -27,6 +27,7 @@ from yamllint.rules import (
     hyphens,
     indentation,
     key_duplicates,
+    key_ordering,
     line_length,
     new_line_at_end_of_file,
     new_lines,
@@ -47,6 +48,7 @@ _RULES = {
     hyphens.ID: hyphens,
     indentation.ID: indentation,
     key_duplicates.ID: key_duplicates,
+    key_ordering.ID: key_ordering,
     line_length.ID: line_length,
     new_line_at_end_of_file.ID: new_line_at_end_of_file,
     new_lines.ID: new_lines,

yamllint/rules/key_ordering.py

@@ -0,0 +1,86 @@
+# -*- coding: utf-8 -*-
+# Copyright (C) 2017 Johannes F. Knauf
+#
+# 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/>.
+
+"""
+Use this rule to enforce alphabetical ordering of keys in mappings.
+
+.. rubric:: Examples
+
+#. With ``key-ordering: {}``
+
+   the following code snippet would **PASS**:
+   ::
+
+    - key 1: v
+      key 2: val
+      key 3: value
+    - {a: 1, b: 2, c: 3}
+
+   the following code snippet would **FAIL**:
+   ::
+
+    - key 2: v
+      key 1: val
+
+   the following code snippet would **FAIL**:
+   ::
+
+    - {b: 1, a: 2}
+"""
+
+import yaml
+
+from yamllint.linter import LintProblem
+
+
+ID = 'key-ordering'
+TYPE = 'token'
+CONF = {}
+
+MAP, SEQ = range(2)
+
+
+class Parent(object):
+    def __init__(self, type):
+        self.type = type
+        self.keys = []
+
+
+def check(conf, token, prev, next, nextnext, context):
+    if 'stack' not in context:
+        context['stack'] = []
+
+    if isinstance(token, (yaml.BlockMappingStartToken,
+                          yaml.FlowMappingStartToken)):
+        context['stack'].append(Parent(MAP))
+    elif isinstance(token, (yaml.BlockSequenceStartToken,
+                            yaml.FlowSequenceStartToken)):
+        context['stack'].append(Parent(SEQ))
+    elif isinstance(token, (yaml.BlockEndToken,
+                            yaml.FlowMappingEndToken,
+                            yaml.FlowSequenceEndToken)):
+        context['stack'].pop()
+    elif (isinstance(token, yaml.KeyToken) and
+          isinstance(next, yaml.ScalarToken)):
+        # This check is done because KeyTokens can be found inside flow
+        # sequences... strange, but allowed.
+        if len(context['stack']) > 0 and context['stack'][-1].type == MAP:
+            if any(next.value < key for key in context['stack'][-1].keys):
+                yield LintProblem(
+                    next.start_mark.line + 1, next.start_mark.column + 1,
+                    'wrong ordering of key "%s" in mapping' % next.value)
+            else:
+                context['stack'][-1].keys.append(next.value)