diff --git a/docs/rules.rst b/docs/rules.rst
index d71d0ae..5fe875f 100644
--- a/docs/rules.rst
+++ b/docs/rules.rst
@@ -69,6 +69,11 @@ indentation
.. automodule:: yamllint.rules.indentation
+key-duplicates
+--------------
+
+.. automodule:: yamllint.rules.key_duplicates
+
line-length
-----------
diff --git a/tests/rules/test_key_duplicates.py b/tests/rules/test_key_duplicates.py
new file mode 100644
index 0000000..b49c0e7
--- /dev/null
+++ b/tests/rules/test_key_duplicates.py
@@ -0,0 +1,156 @@
+# -*- 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 .
+
+from tests.common import RuleTestCase
+
+
+class KeyDuplicatesTestCase(RuleTestCase):
+ rule_id = 'key-duplicates'
+
+ def test_disabled(self):
+ conf = 'key-duplicates: disable'
+ self.check('---\n'
+ 'block mapping:\n'
+ ' key: a\n'
+ ' otherkey: b\n'
+ ' key: c\n', conf)
+ self.check('---\n'
+ 'flow mapping:\n'
+ ' {key: a, otherkey: b, key: c}\n', conf)
+ self.check('---\n'
+ 'duplicated twice:\n'
+ ' - k: a\n'
+ ' ok: b\n'
+ ' k: c\n'
+ ' k: d\n', conf)
+ self.check('---\n'
+ 'duplicated twice:\n'
+ ' - {k: a, ok: b, k: c, k: d}\n', conf)
+ self.check('---\n'
+ 'multiple duplicates:\n'
+ ' a: 1\n'
+ ' b: 2\n'
+ ' c: 3\n'
+ ' d: 4\n'
+ ' d: 5\n'
+ ' b: 6\n', conf)
+ self.check('---\n'
+ 'multiple duplicates:\n'
+ ' {a: 1, b: 2, c: 3, d: 4, d: 5, b: 6}\n', conf)
+ self.check('---\n'
+ 'at: root\n'
+ 'multiple: times\n'
+ 'at: root\n', conf)
+ self.check('---\n'
+ 'nested but OK:\n'
+ ' a: {a: {a: 1}}\n'
+ ' b:\n'
+ ' b: 2\n'
+ ' c: 3\n', conf)
+ self.check('---\n'
+ 'nested duplicates:\n'
+ ' a: {a: 1, a: 1}\n'
+ ' b:\n'
+ ' c: 3\n'
+ ' d: 4\n'
+ ' d: 4\n'
+ ' b: 2\n', conf)
+ self.check('---\n'
+ 'duplicates with many styles: 1\n'
+ '"duplicates with many styles": 1\n'
+ '\'duplicates with many styles\': 1\n'
+ '? duplicates with many styles\n'
+ ': 1\n'
+ '? >-\n'
+ ' duplicates with\n'
+ ' many styles\n'
+ ': 1\n', conf)
+
+ def test_enabled(self):
+ conf = 'key-duplicates: {}'
+ self.check('---\n'
+ 'block mapping:\n'
+ ' key: a\n'
+ ' otherkey: b\n'
+ ' key: c\n', conf,
+ problem=(5, 3))
+ self.check('---\n'
+ 'flow mapping:\n'
+ ' {key: a, otherkey: b, key: c}\n', conf,
+ problem=(3, 25))
+ self.check('---\n'
+ 'duplicated twice:\n'
+ ' - k: a\n'
+ ' ok: b\n'
+ ' k: c\n'
+ ' k: d\n', conf,
+ problem1=(5, 5), problem2=(6, 5))
+ self.check('---\n'
+ 'duplicated twice:\n'
+ ' - {k: a, ok: b, k: c, k: d}\n', conf,
+ problem1=(3, 19), problem2=(3, 25))
+ self.check('---\n'
+ 'multiple duplicates:\n'
+ ' a: 1\n'
+ ' b: 2\n'
+ ' c: 3\n'
+ ' d: 4\n'
+ ' d: 5\n'
+ ' b: 6\n', conf,
+ problem1=(7, 3), problem2=(8, 3))
+ self.check('---\n'
+ 'multiple duplicates:\n'
+ ' {a: 1, b: 2, c: 3, d: 4, d: 5, b: 6}\n', conf,
+ problem1=(3, 28), problem2=(3, 34))
+ self.check('---\n'
+ 'at: root\n'
+ 'multiple: times\n'
+ 'at: root\n', conf,
+ problem=(4, 1))
+ self.check('---\n'
+ 'nested but OK:\n'
+ ' a: {a: {a: 1}}\n'
+ ' b:\n'
+ ' b: 2\n'
+ ' c: 3\n', conf)
+ self.check('---\n'
+ 'nested duplicates:\n'
+ ' a: {a: 1, a: 1}\n'
+ ' b:\n'
+ ' c: 3\n'
+ ' d: 4\n'
+ ' d: 4\n'
+ ' b: 2\n', conf,
+ problem1=(3, 13), problem2=(7, 5), problem3=(8, 3))
+ self.check('---\n'
+ 'duplicates with many styles: 1\n'
+ '"duplicates with many styles": 1\n'
+ '\'duplicates with many styles\': 1\n'
+ '? duplicates with many styles\n'
+ ': 1\n'
+ '? >-\n'
+ ' duplicates with\n'
+ ' many styles\n'
+ ': 1\n', conf,
+ problem1=(3, 1), problem2=(4, 1), problem3=(5, 3),
+ problem4=(7, 3))
+
+ def test_key_tokens_in_flow_sequences(self):
+ conf = 'key-duplicates: {}'
+ self.check('---\n'
+ '[\n'
+ ' flow: sequence, with, key: value, mappings\n'
+ ']\n', conf)
diff --git a/yamllint/conf/default.yml b/yamllint/conf/default.yml
index 2b5aa3c..71bd825 100644
--- a/yamllint/conf/default.yml
+++ b/yamllint/conf/default.yml
@@ -34,6 +34,7 @@ rules:
spaces: 2
indent-sequences: yes
check-multi-line-strings: no
+ key-duplicates: {}
line-length:
max: 80
allow-non-breakable-words: yes
diff --git a/yamllint/rules/__init__.py b/yamllint/rules/__init__.py
index 8a7dd23..6e82970 100644
--- a/yamllint/rules/__init__.py
+++ b/yamllint/rules/__init__.py
@@ -26,6 +26,7 @@ from yamllint.rules import (
empty_lines,
hyphens,
indentation,
+ key_duplicates,
line_length,
new_line_at_end_of_file,
new_lines,
@@ -44,6 +45,7 @@ _RULES = {
empty_lines.ID: empty_lines,
hyphens.ID: hyphens,
indentation.ID: indentation,
+ key_duplicates.ID: key_duplicates,
line_length.ID: line_length,
new_line_at_end_of_file.ID: new_line_at_end_of_file,
new_lines.ID: new_lines,
diff --git a/yamllint/rules/key_duplicates.py b/yamllint/rules/key_duplicates.py
new file mode 100644
index 0000000..9f879f0
--- /dev/null
+++ b/yamllint/rules/key_duplicates.py
@@ -0,0 +1,99 @@
+# -*- 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 .
+
+"""
+Use this rule to prevent multiple entries with the same key in mappings.
+
+.. rubric:: Examples
+
+#. With ``key-duplicates: {}``
+
+ 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 1: v
+ key 2: val
+ key 1: value
+
+ the following code snippet would **FAIL**:
+ ::
+
+ - {a: 1, b: 2, b: 3}
+
+ the following code snippet would **FAIL**:
+ ::
+
+ duplicated key: 1
+ "duplicated key": 2
+
+ other duplication: 1
+ ? >-
+ other
+ duplication
+ : 2
+"""
+
+import yaml
+
+from yamllint.linter import LintProblem
+
+
+ID = 'key-duplicates'
+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, 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 next.value in context['stack'][-1].keys:
+ yield LintProblem(
+ next.start_mark.line + 1, next.start_mark.column + 1,
+ 'duplication of key "%s" in mapping' % next.value)
+ else:
+ context['stack'][-1].keys.append(next.value)