added ability to exclude current rule with an ignore comment placed in…

[n1kk]

Proposed changes

Added a feature to ignore current class with a comment /* purgecss ignore current */ inside of it.

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist

• Lint and unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

PR to docs: FullHuman/purgecss-docs#33

Further comments

At my current project we use postcss together with scss and the problem arises when we need to ignore lists of generated classes that will be used dynamically. There's to much to keep them in the whitelist or regexp patterns array and it gets problematic to maintain it, and existing ignore comments do not really cover our case easily.

If we use /* purgecss ignore */ before generated class then it doesn't work since the comment is left in the body of parent class:

.parent {
	/* ... */
	@for $i from 1 through $max-size {
		/* purgecss ignore */
		&.size-#{$i} {
			/* ... */
		}
	}
}

turns to

.parent {
	/* ... */

	/* purgecss ignore */
	/* purgecss ignore */
	/* purgecss ignore */
}

.parent .size-1 { /* ... */ }
.parent .size-2 { /* ... */ }
.parent .size-3 { /* ... */ }

And we can't really use ignore start and end comments because scss files have all classes nested under one parent so the whole file will be ignored. We want to ignore only lists that are used dynamically and there is no code reference to them.

Adding comment for ignoring current class easily fixes the issue and doesn't require any list maintaining. If style files are gone no dead code is left behind.