Add ignore-regex option to comments rule

[peschmae]

Fixes #545

This adds a ignore-regex flag to the comments rule.

If a comment matches the regex, require-starting-space as well as min-spaces-from-content are skipped.

The regex is only matched against the comment itself, and not against the full line.

[coveralls]

coverage: 99.826% (+0.001%) from 99.825%
when pulling fd1f8ca on peschmae:feat/comment-ignore-regex
into d5b6c4a on adrienverge:master.

[adrienverge]

Hello @peschmae, thanks for contributing!

This looks good, but I have a few requests.

1. First, I disagree with myself of 2021 when I proposed ignore-regex as the option name. Indeed, other rules don't use "regex" in their option names when their content should be a regex. Similarly, rules don't tell "option-…-string" when their value should be a string.

   Instead, I propose ignore-comments. This will allow adding ignore-lines in the future, if one day we want to silent errors based on the preceding YAML line contents, in case of inline comment:

   part of the line that should match the regex  # comment

2. Can you reword Fixes #545 to Partially fixes #545 ? Because the original request is about silenting both the comments and line-length rules, so in my opinion the issue #545 should remain open.

3. Finally, write a good commit message (basically: the commit title should be comments: … and the message could be what you wrote in the first PR message).

[adrienverge]

• You can remove the comment: the code is self-explainatory.
• if len(conf['ignore-regex']) > 0 is not needed, because any([]) is false.
• Can you please add an empty line afterwards, like 7 lines below ↓, for logical separation?

Suggested change

	# If the comment matched the ignore-regex, we don't perform any checks
	if (len(conf['ignore-regex']) > 0 and
	any(re.search(r, str(comment))
	for r in conf['ignore-regex'])):
	return
	if any(re.search(r, str(comment)) for r in conf['ignore-regex']):

[adrienverge]

• There are multiple syntax for regexes, here it's PCRE regexes. We mention it in key-ordering and quoted-strings documentations, so let's do it here too 👍
• I have a proposal that I find slightly clearer about inline comments:

Suggested change

	* ``ignore-regex`` is used to exclude specific comments from this check.
	Only the comment itself will be matched to the regex, not the whole line on
	inline comments.
	* ``ignore-comments`` is a list of PCRE regexes to exclude specific comments
	from this check. For inline comments, only the comment itself will be matched
	to the regex, not the whole line.

What do you think?

[adrienverge]

I propose to:

• merge both examples to ease the reader understanding (both cases pass),
• give an example where the regex matches a part of the comment.

This would yield:

Suggested change

	#. With ``comments: {ignore-regex: [^#cloud-config]}``
	the following code snippet would **PASS**:
	::
	#cloud-config
	#. With ``comments: {ignore-regex: [^#noqa]}``
	the following code snippet would **PASS**:
	::
	enabled: true #noqa
	#. With ``comments: {ignore-regex: [^#cloud-config, ^#noqa]}``
	the following code snippet would **PASS**:
	::
	#cloud-config
	import lib #noqa: E402

(This doesn't make sense to fix a Cloud-init file with Python code, but at least it's short and readable.)

[adrienverge]

To check close-but-not-exact matches:

Suggested change

	'#but not this\n', conf,
	problem1=(3, 2))
	'#but not this\n'
	'# ignore this\n', conf,
	problem1=(3, 2),
	problem2=(4, 2))

[binaryDiv]

This would be a very helpful feature! Is there any news on it?