Add custom PHPCS sniff to warn against usage of empty()

[ShyamGadde]

Summary

Fixes #1219

Relevant Technical Choices

The dominant-color-images, performance-lab, and webp-uploads plugins have been ignored by the custom PHPCS sniff configuration, similar to the approach used for PHPStan.

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Co-authored-by: ShyamGadde <[email protected]>
Co-authored-by: swissspidy <[email protected]>
Co-authored-by: westonruter <[email protected]>
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[swissspidy]

Why do we need to write and maintain a custom PHPCS sniff for this when https://github.com/phpstan/phpstan-strict-rules already catches that just fine? 🤔

[westonruter]

Right, the disallowedEmpty rule from phpstan-strict-rules should do what we need. And this is already being applied, with the exceptions being for the same plugins excluded in this PR.

performance/phpstan.neon.dist

Lines 68 to 75 in b6e5c5a

	-
	# TODO: Remove this to fix https://github.com/WordPress/performance/issues/1219
	identifier: empty.notAllowed
	paths:
	- */tests/*
	- plugins/dominant-color-images
	- plugins/performance-lab
	- plugins/webp-uploads

[ShyamGadde]

That’s correct—PHPStan does show the following error:

Construct empty() is not allowed. Use more strict comparison.

Given that phpstan-strict-rules already handles this effectively, this PR doesn’t seem necessary.

Thank you for pointing this out! I’ll go ahead and close it now.