line_length: Extract inline logic to new config option

This commit extracts the inline mappings logic defined in the previous
commit to a separate config option, as suggested by @adrienverge. I'll
squash this into the previous commit if the change is accepted. (I named
the option slightly differently to what was suggested as I think my
proposal reads better without consulting the docs: I'd be happy to
reconsider this.)

tests/rules/test_line_length.py

@@ -85,7 +85,8 @@ class LineLengthTestCase(RuleTestCase):
                    '  - https://localhost/very/very/long/url\n'
                    '...\n', conf)
         self.check('---\n'
-                   'long_line: http://localhost/very/very/long/url\n', conf)
+                   'long_line: http://localhost/very/very/long/url\n', conf,
+                   problem=(2, 21))
 
         conf = 'line-length: {max: 20, allow-non-breakable-words: no}'
         self.check('---\n' + 30 * 'A' + '\n', conf, problem=(2, 21))
@@ -111,3 +112,8 @@ class LineLengthTestCase(RuleTestCase):
         self.check('---\n'
                    'long_line: http://localhost/very/very/long/url\n'
                    '...\n', conf, problem=(2, 21))
+
+        conf = 'line-length: {max: 20, ' \
+               'allow-non-breakable-inline-mappings: yes}'
+        self.check('---\n'
+                   'long_line: http://localhost/very/very/long/url\n', conf)

yamllint/conf/default.yaml

@@ -38,6 +38,7 @@ rules:
   line-length:
     max: 80
     allow-non-breakable-words: yes
+    allow-non-breakable-inline-mappings: no
   new-line-at-end-of-file: enable
   new-lines:
     type: unix

yamllint/conf/relaxed.yaml

@@ -25,3 +25,4 @@ rules:
     indent-sequences: consistent
   line-length:
     level: warning
+    allow-non-breakable-inline-mappings: yes

yamllint/rules/line_length.py

@@ -23,6 +23,8 @@ Use this rule to set a limit to lines length.
 * ``allow-non-breakable-words`` is used to allow non breakable words (without
   spaces inside) to overflow the limit. This is useful for long URLs, for
   instance. Use ``yes`` to allow, ``no`` to forbid.
+* ``allow-non-breakable-inline-mappings`` implies ``allow-non-breakable-words``
+  and extends it to also allow non-breakable words in inline mappings.
 
 .. rubric:: Examples
 
@@ -61,6 +63,19 @@ Use this rule to set a limit to lines length.
 
     - this line is waaaaaaaaaaaaaay too long but could be easily split...
 
+   and the following code snippet would also **FAIL**:
+   ::
+
+    - foobar: http://localhost/very/very/very/very/very/very/very/very/long/url
+
+#. With ``line-length: {max: 60, allow-non-breakable-words: yes,
+   allow-non-breakable-inline-mappings: yes}``
+
+   the following code snippet would **PASS**:
+   ::
+
+    - foobar: http://localhost/very/very/very/very/very/very/very/very/long/url
+
 #. With ``line-length: {max: 60, allow-non-breakable-words: no}``
 
    the following code snippet would **FAIL**:
@@ -80,11 +95,14 @@ from yamllint.linter import LintProblem
 ID = 'line-length'
 TYPE = 'line'
 CONF = {'max': int,
-        'allow-non-breakable-words': bool}
+        'allow-non-breakable-words': bool,
+        'allow-non-breakable-inline-mappings': bool}
 
 
 def check(conf, line):
     if line.end - line.start > conf['max']:
+        conf['allow-non-breakable-words'] |= \
+            conf['allow-non-breakable-inline-mappings']
         if conf['allow-non-breakable-words']:
             start = line.start
             while start < line.end and line.buffer[start] == ' ':
@@ -97,10 +115,11 @@ def check(conf, line):
                 if line.buffer.find(' ', start, line.end) == -1:
                     return
 
-                line_yaml = yaml.safe_load(line.content)
-                if (isinstance(line_yaml, dict) and
-                        ' ' not in line_yaml.popitem()[1]):
-                    return
+                if conf['allow-non-breakable-inline-mappings']:
+                    line_yaml = yaml.safe_load(line.content)
+                    if (isinstance(line_yaml, dict) and
+                            ' ' not in line_yaml.popitem()[1]):
+                        return
 
         yield LintProblem(line.line_no, conf['max'] + 1,
                           'line too long (%d > %d characters)' %