config: Do not require all rule options to be set

Before, it was required to specify all the options when customizing a
rule. For instance, one could use `empty-lines: enable` or `empty-lines:
{max: 1, max-start: 2, max-end: 2}`, but not just `empty-lines: {max:
1}` (it would fail with *invalid config: missing option "max-start" for
rule "empty-lines"*).

This was a minor problem for users, but it prevented the addition of new
options to existing rules, see [1] for an example. If a new option was
added, updating yamllint for all users that customize the rule would
produce a crash (*invalid config: missing option ...*).

To avoid that, let's embed default values inside the rules themselves,
instead of keeping them in `conf/default.yaml`.

This refactor should not have any impact on existing projects. I've
manually checked that it did not change the output of tests, on
different projects:
- ansible/ansible: `test/runner/ansible-test sanity --python 3.7 --test yamllint`
- ansible/molecule: `yamllint -s test/ molecule/`
- Neo23x0/sigma: `make test-yaml`
- markstory/lint-review: `yamllint .`

[1]: https://github.com/adrienverge/yamllint/pull/151

yamllint/conf/default.yaml

@@ -1,59 +1,28 @@
 ---
 
 rules:
-  braces:
-    min-spaces-inside: 0
-    max-spaces-inside: 0
-    min-spaces-inside-empty: -1
-    max-spaces-inside-empty: -1
-  brackets:
-    min-spaces-inside: 0
-    max-spaces-inside: 0
-    min-spaces-inside-empty: -1
-    max-spaces-inside-empty: -1
-  colons:
-    max-spaces-before: 0
-    max-spaces-after: 1
-  commas:
-    max-spaces-before: 0
-    min-spaces-after: 1
-    max-spaces-after: 1
+  braces: enable
+  brackets: enable
+  colons: enable
+  commas: enable
   comments:
     level: warning
-    require-starting-space: true
-    min-spaces-from-content: 2
   comments-indentation:
     level: warning
   document-end: disable
   document-start:
     level: warning
-    present: true
-  empty-lines:
-    max: 2
-    max-start: 0
-    max-end: 0
-  quoted-strings: disable
-  empty-values:
-    forbid-in-block-mappings: false
-    forbid-in-flow-mappings: false
-  hyphens:
-    max-spaces-after: 1
-  indentation:
-    spaces: consistent
-    indent-sequences: true
-    check-multi-line-strings: false
+  empty-lines: enable
+  empty-values: enable
+  hyphens: enable
+  indentation: enable
   key-duplicates: enable
   key-ordering: disable
-  line-length:
-    max: 80
-    allow-non-breakable-words: true
-    allow-non-breakable-inline-mappings: false
+  line-length: enable
   new-line-at-end-of-file: enable
-  new-lines:
-    type: unix
-  octal-values:
-    forbid-implicit-octal: false
-    forbid-explicit-octal: false
+  new-lines: enable
+  octal-values: enable
+  quoted-strings: disable
   trailing-spaces: enable
   truthy:
     level: warning

yamllint/config.py

@@ -74,6 +74,11 @@ class YamlLintConfig(object):
             raise YamlLintConfigError('invalid config: not a dict')
 
         self.rules = conf.get('rules', {})
+        for rule in self.rules:
+            if self.rules[rule] == 'enable':
+                self.rules[rule] = {}
+            elif self.rules[rule] == 'disable':
+                self.rules[rule] = False
 
         # Does this conf override another conf that we need to load?
         if 'extends' in conf:
@@ -102,10 +107,8 @@ class YamlLintConfig(object):
 
 
 def validate_rule_conf(rule, conf):
-    if conf is False or conf == 'disable':
+    if conf is False:  # disable
         return False
-    elif conf == 'enable':
-        conf = {}
 
     if isinstance(conf, dict):
         if ('ignore' in conf and
@@ -123,6 +126,7 @@ def validate_rule_conf(rule, conf):
                 'invalid config: level should be "error" or "warning"')
 
         options = getattr(rule, 'CONF', {})
+        options_default = getattr(rule, 'DEFAULT', {})
         for optkey in conf:
             if optkey in ('ignore', 'level'):
                 continue
@@ -143,9 +147,7 @@ def validate_rule_conf(rule, conf):
                         % (optkey, rule.ID, options[optkey].__name__))
         for optkey in options:
             if optkey not in conf:
-                raise YamlLintConfigError(
-                    'invalid config: missing option "%s" for rule "%s"' %
-                    (optkey, rule.ID))
+                conf[optkey] = options_default[optkey]
     else:
         raise YamlLintConfigError(('invalid config: rule "%s": should be '
                                    'either "enable", "disable" or a dict')

yamllint/rules/braces.py

@@ -101,6 +101,10 @@ CONF = {'min-spaces-inside': int,
         'max-spaces-inside': int,
         'min-spaces-inside-empty': int,
         'max-spaces-inside-empty': int}
+DEFAULT = {'min-spaces-inside': 0,
+           'max-spaces-inside': 0,
+           'min-spaces-inside-empty': -1,
+           'max-spaces-inside-empty': -1}
 
 
 def check(conf, token, prev, next, nextnext, context):

yamllint/rules/brackets.py

@@ -102,6 +102,10 @@ CONF = {'min-spaces-inside': int,
         'max-spaces-inside': int,
         'min-spaces-inside-empty': int,
         'max-spaces-inside-empty': int}
+DEFAULT = {'min-spaces-inside': 0,
+           'max-spaces-inside': 0,
+           'min-spaces-inside-empty': -1,
+           'max-spaces-inside-empty': -1}
 
 
 def check(conf, token, prev, next, nextnext, context):

yamllint/rules/colons.py

@@ -79,6 +79,8 @@ ID = 'colons'
 TYPE = 'token'
 CONF = {'max-spaces-before': int,
         'max-spaces-after': int}
+DEFAULT = {'max-spaces-before': 0,
+           'max-spaces-after': 1}
 
 
 def check(conf, token, prev, next, nextnext, context):

yamllint/rules/commas.py

@@ -103,6 +103,9 @@ TYPE = 'token'
 CONF = {'max-spaces-before': int,
         'min-spaces-after': int,
         'max-spaces-after': int}
+DEFAULT = {'max-spaces-before': 0,
+           'min-spaces-after': 1,
+           'max-spaces-after': 1}
 
 
 def check(conf, token, prev, next, nextnext, context):

yamllint/rules/comments.py

@@ -68,6 +68,8 @@ ID = 'comments'
 TYPE = 'comment'
 CONF = {'require-starting-space': bool,
         'min-spaces-from-content': int}
+DEFAULT = {'require-starting-space': True,
+           'min-spaces-from-content': 2}
 
 
 def check(conf, comment):

yamllint/rules/document_end.py

@@ -82,6 +82,7 @@ from yamllint.linter import LintProblem
 ID = 'document-end'
 TYPE = 'token'
 CONF = {'present': bool}
+DEFAULT = {'present': True}
 
 
 def check(conf, token, prev, next, nextnext, context):

yamllint/rules/document_start.py

@@ -72,6 +72,7 @@ from yamllint.linter import LintProblem
 ID = 'document-start'
 TYPE = 'token'
 CONF = {'present': bool}
+DEFAULT = {'present': True}
 
 
 def check(conf, token, prev, next, nextnext, context):

yamllint/rules/empty_lines.py

@@ -58,6 +58,9 @@ TYPE = 'line'
 CONF = {'max': int,
         'max-start': int,
         'max-end': int}
+DEFAULT = {'max': 2,
+           'max-start': 0,
+           'max-end': 0}
 
 
 def check(conf, line):

yamllint/rules/empty_values.py

@@ -75,6 +75,8 @@ ID = 'empty-values'
 TYPE = 'token'
 CONF = {'forbid-in-block-mappings': bool,
         'forbid-in-flow-mappings': bool}
+DEFAULT = {'forbid-in-block-mappings': False,
+           'forbid-in-flow-mappings': False}
 
 
 def check(conf, token, prev, next, nextnext, context):

yamllint/rules/hyphens.py

@@ -76,6 +76,7 @@ from yamllint.rules.common import spaces_after
 ID = 'hyphens'
 TYPE = 'token'
 CONF = {'max-spaces-after': int}
+DEFAULT = {'max-spaces-after': 1}
 
 
 def check(conf, token, prev, next, nextnext, context):

yamllint/rules/indentation.py

@@ -201,6 +201,9 @@ TYPE = 'token'
 CONF = {'spaces': (int, 'consistent'),
         'indent-sequences': (bool, 'whatever', 'consistent'),
         'check-multi-line-strings': bool}
+DEFAULT = {'spaces': 'consistent',
+           'indent-sequences': True,
+           'check-multi-line-strings': False}
 
 ROOT, B_MAP, F_MAP, B_SEQ, F_SEQ, B_ENT, KEY, VAL = range(8)
 labels = ('ROOT', 'B_MAP', 'F_MAP', 'B_SEQ', 'F_SEQ', 'B_ENT', 'KEY', 'VAL')

yamllint/rules/key_duplicates.py

@@ -61,7 +61,6 @@ from yamllint.linter import LintProblem
 
 ID = 'key-duplicates'
 TYPE = 'token'
-CONF = {}
 
 MAP, SEQ = range(2)
 

yamllint/rules/key_ordering.py

@@ -72,7 +72,6 @@ from yamllint.linter import LintProblem
 
 ID = 'key-ordering'
 TYPE = 'token'
-CONF = {}
 
 MAP, SEQ = range(2)
 

yamllint/rules/line_length.py

@@ -102,6 +102,9 @@ TYPE = 'line'
 CONF = {'max': int,
         'allow-non-breakable-words': bool,
         'allow-non-breakable-inline-mappings': bool}
+DEFAULT = {'max': 80,
+           'allow-non-breakable-words': True,
+           'allow-non-breakable-inline-mappings': False}
 
 
 def check_inline_mapping(line):

yamllint/rules/new_lines.py

@@ -30,6 +30,7 @@ from yamllint.linter import LintProblem
 ID = 'new-lines'
 TYPE = 'line'
 CONF = {'type': ('unix', 'dos')}
+DEFAULT = {'type': 'unix'}
 
 
 def check(conf, line):

yamllint/rules/octal_values.py

@@ -66,6 +66,8 @@ ID = 'octal-values'
 TYPE = 'token'
 CONF = {'forbid-implicit-octal': bool,
         'forbid-explicit-octal': bool}
+DEFAULT = {'forbid-implicit-octal': False,
+           'forbid-explicit-octal': False}
 
 
 def check(conf, token, prev, next, nextnext, context):

yamllint/rules/quoted_strings.py

@@ -46,6 +46,7 @@ from yamllint.linter import LintProblem
 ID = 'quoted-strings'
 TYPE = 'token'
 CONF = {'quote-type': ('any', 'single', 'double')}
+DEFAULT = {'quote-type': 'any'}
 
 
 def check(conf, token, prev, next, nextnext, context):

yamllint/rules/truthy.py

@@ -71,7 +71,6 @@ from yamllint.linter import LintProblem
 
 ID = 'truthy'
 TYPE = 'token'
-CONF = {}
 
 TRUTHY = ['YES', 'Yes', 'yes',
           'NO', 'No', 'no',