Add a pair of rules to forbid flow collection styles as needed

Add a pair of new rules to forbid flow collection styles (flow mapping
and flow sequence) as needed, add those test cases and update default
configuration to disable these rules by default.

tests/test_flow_mapping.py

@@ -0,0 +1,34 @@
+# -*- coding: utf-8 -*-
+# Copyright (C) 2020 Satoru SATOH
+#
+# SPDX-License-Identifier: GPL-3.0-or-later
+#
+# pylint: disable=missing-function-docstring
+"""test cases for flow-mapping rule.
+"""
+import tests.common
+
+
+class FlowMappingTestCase(tests.common.RuleTestCase):
+    """Flow Mapping test cases.
+    """
+    rule_id = 'flow-mapping'
+
+    def test_disabled(self):
+        conf = 'flow-mapping: disable'
+        self.check('---\n'
+                   '1: {"a": 2}\n', conf)
+
+    def test_enabled(self):
+        conf = 'flow-mapping: enable\n'
+        self.check('---\n'
+                   '1: {"a": 2}\n',
+                   conf, problem1=(2, 4))
+        self.check('---\n'
+                   '1:\n'
+                   '  a: 2\n', conf)
+        self.check('---\n'
+                   '1: {\n'
+                   '  "a": 2,\n'
+                   '}\n', conf,
+                   problem1=(2, 4))

tests/test_flow_sequence.py

@@ -0,0 +1,36 @@
+# -*- coding: utf-8 -*-
+# Copyright (C) 2020 Satoru SATOH
+#
+# SPDX-License-Identifier: GPL-3.0-or-later
+#
+# pylint: disable=missing-function-docstring
+"""test cases for  flow-sequence rule.
+"""
+import tests.common
+
+
+class FlowSequenceTestCase(tests.common.RuleTestCase):
+    """Flow Sequence test cases.
+    """
+    rule_id = 'flow-sequence'
+
+    def test_disabled(self):
+        conf = 'flow-sequence: disable'
+        self.check('---\n'
+                   '1: [2, 3]\n', conf)
+
+    def test_enabled(self):
+        conf = 'flow-sequence: enable\n'
+        self.check('---\n'
+                   '1: [2, 3]\n',
+                   conf, problem1=(2, 4))
+        self.check('---\n'
+                   '1:\n'
+                   '  - 2\n'
+                   '  - 3\n', conf)
+        self.check('---\n'
+                   '[\n'
+                   '  1,\n'
+                   '  2\n'
+                   ']\n', conf,
+                   problem1=(2, 1))

yamllint/conf/default.yaml

@@ -19,6 +19,8 @@ rules:
     level: warning
   empty-lines: enable
   empty-values: disable
+  flow-mapping: disable
+  flow-sequence: disable
   hyphens: enable
   indentation: enable
   key-duplicates: enable

yamllint/conf/relaxed.yaml

@@ -18,6 +18,8 @@ rules:
   document-start: disable
   empty-lines:
     level: warning
+  flow-mapping: disable
+  flow-sequence: disable
   hyphens:
     level: warning
   indentation:

yamllint/rules/__init__.py

@@ -25,6 +25,8 @@ from yamllint.rules import (
     document_start,
     empty_lines,
     empty_values,
+    flow_mapping,
+    flow_sequence,
     hyphens,
     indentation,
     key_duplicates,
@@ -49,6 +51,8 @@ _RULES = {
     document_start.ID: document_start,
     empty_lines.ID: empty_lines,
     empty_values.ID: empty_values,
+    flow_mapping.ID: flow_mapping,
+    flow_sequence.ID: flow_sequence,
     hyphens.ID: hyphens,
     indentation.ID: indentation,
     key_duplicates.ID: key_duplicates,

yamllint/rules/flow_mapping.py

@@ -0,0 +1,42 @@
+#
+# Copyright (C) 2020 Satoru SATOH
+# SPDX-License-Identifier: GPL-3.0-or-later
+#
+"""
+Use this rule to forbid flow mappings of which content is denoted by
+surrounding "{" and "}".
+
+.. rubric:: Examples
+
+#. The following code snippet would **PASS**:
+   ::
+
+    foo:
+      bar: 1
+    baz:
+      a: b
+
+#. The following code snippet would **FAIL**:
+   ::
+
+    foo: {'bar': 1}
+    baz: {
+      'a': 'b'
+    }
+"""
+import yaml
+
+from yamllint.linter import LintProblem
+
+
+ID = 'flow-mapping'
+TYPE = 'token'
+
+
+def check(conf, token, _prev, _next, _nextnext, _context):
+    """Check if the toke starts flow mapping is found.
+    """
+    if isinstance(token, yaml.FlowMappingStartToken):
+        yield LintProblem(token.start_mark.line + 1,
+                          token.start_mark.column + 1,
+                          "Flow mappings are forbidden.")

yamllint/rules/flow_sequence.py

@@ -0,0 +1,39 @@
+#
+# Copyright (C) 2020 Satoru SATOH
+# SPDX-License-Identifier: GPL-3.0-or-later
+#
+"""
+Use this rule to forbid flow sequences of which content is denoted by
+surrounding "[" and "]".
+
+.. rubric:: Examples
+
+#. The following code snippet would **PASS**:
+   ::
+
+    foo:
+      - bar
+      - baz
+
+#. The following code snippet would **FAIL**:
+   ::
+
+    foo: ['bar', 'baz']
+
+"""
+import yaml
+
+from yamllint.linter import LintProblem
+
+
+ID = 'flow-sequence'
+TYPE = 'token'
+
+
+def check(conf, token, _prev, _next, _nextnext, _context):
+    """Check if the toke starts flow sequnce is found.
+    """
+    if isinstance(token, yaml.FlowSequenceStartToken):
+        yield LintProblem(token.start_mark.line + 1,
+                          token.start_mark.column + 1,
+                          "Flow Sequences are forbidden.")