quoted-strings: Add quote-type: consistent

Strings in a document may be single or double, but must be consistent.
The first string found is assumed to be the canonical quote type, and
any subsequent quotes will be compared to it.

Closes: #763

Author: rfinnie

tests/rules/test_quoted_strings.py

@@ -186,6 +186,47 @@ def test_quote_type_double(self):
                    '   word 2"\n',
                    conf, problem1=(9, 3))
 
+    def test_quote_type_consistent(self):
+        conf = 'quoted-strings: {quote-type: consistent}'
+        self.check('---\n'
+                   'string1: "foo"\n'
+                   'string2: "bar"\n'
+                   'string3: \'baz\'\n'              # fails
+                   'string4: "quux"\n',
+                   conf, problem1=(4, 10))
+
+        conf = ('quoted-strings:\n'
+                '  quote-type: consistent\n'
+                '  check-keys: true\n')
+        self.check('---\n'
+                   '"string1": "foo"\n'
+                   'string2: "bar"\n'                # fails
+                   '\'string3\': "baz"\n'            # fails
+                   '"string4": {"key": "val"}\n'
+                   '"string5": {\'key\': "val"}\n',  # fails
+                   conf, problem1=(3, 1), problem2=(4, 1), problem3=(6, 13))
+
+        conf = ('quoted-strings:\n'
+                '  quote-type: consistent\n'
+                '  check-keys: true\n'
+                '  required: false\n')
+        self.check('---\n'
+                   'string1: \'foo\'\n'
+                   'string2: "bar"\n'               # fails
+                   'string3: \'baz\'\n'
+                   'string4: {\'key\': "val"}\n'    # fails
+                   'string5: {"key": \'val\'}\n'    # fails
+                   'string6:\n'
+                   '  \'key\': "val"\n'             # fails
+                   'string7:\n'
+                   '  "key": \'val\'\n'             # fails
+                   'string8:\n'
+                   '  "string"\n'                   # fails
+                   'string9: >\n'
+                   '  "string"\n',
+                   conf, problem1=(3, 10), problem2=(5, 18), problem3=(6, 11),
+                   problem4=(8, 10), problem5=(10, 3), problem6=(12, 3))
+
     def test_any_quotes_not_required(self):
         conf = 'quoted-strings: {quote-type: any, required: false}\n'
 

yamllint/rules/quoted_strings.py

@@ -139,6 +139,20 @@
 
     foo: 'bar"baz'
 
+#. With ``quoted-strings: {quote-type: consistent}``
+
+   the following code snippet would **PASS**:
+   ::
+
+    foo: 'bar'
+    baz: 'quux'
+
+   the following code snippet would **FAIL**:
+   ::
+
+    foo: 'bar'
+    baz: "quux"
+
 #. With ``quoted-strings: {required: only-when-needed, check-keys: true,
    extra-required: ["[:]"]}``
 
@@ -161,7 +175,7 @@
 
 ID = 'quoted-strings'
 TYPE = 'token'
-CONF = {'quote-type': ('any', 'single', 'double'),
+CONF = {'quote-type': ('any', 'single', 'double', 'consistent'),
         'required': (True, False, 'only-when-needed'),
         'extra-required': [str],
         'extra-allowed': [str],
@@ -198,7 +212,14 @@ def VALIDATE(conf):
     list('-+0123456789'))
 
 
-def _quote_match(quote_type, token_style):
+def _quote_match(quote_type, token_style, context):
+    if quote_type == 'consistent' and token_style is not None:
+        # The canonical token style in a document is assumed to be the first
+        # one found for the purpose of 'consistent'
+        if 'quoted_strings_consistent_token_style' not in context:
+            context['quoted_strings_consistent_token_style'] = token_style
+        return context['quoted_strings_consistent_token_style'] == token_style
+
     return ((quote_type == 'any') or
             (quote_type == 'single' and token_style == "'") or
             (quote_type == 'double' and token_style == '"'))
@@ -294,15 +315,15 @@ def check(conf, token, prev, next, nextnext, context):
 
         # Quotes are mandatory and need to match config
         if (token.style is None or
-            not (_quote_match(quote_type, token.style) or
+            not (_quote_match(quote_type, token.style, context) or
                  (conf['allow-quoted-quotes'] and _has_quoted_quotes(token)))):
             msg = f"string {node} is not quoted with {quote_type} quotes"
 
     elif conf['required'] is False:
 
         # Quotes are not mandatory but when used need to match config
         if (token.style and
-                not _quote_match(quote_type, token.style) and
+                not _quote_match(quote_type, token.style, context) and
                 not (conf['allow-quoted-quotes'] and
                      _has_quoted_quotes(token))):
             msg = f"string {node} is not quoted with {quote_type} quotes"
@@ -328,7 +349,7 @@ def check(conf, token, prev, next, nextnext, context):
 
         # But when used need to match config
         elif (token.style and
-              not _quote_match(quote_type, token.style) and
+              not _quote_match(quote_type, token.style, context) and
               not (conf['allow-quoted-quotes'] and _has_quoted_quotes(token))):
             msg = f"string {node} is not quoted with {quote_type} quotes"