postcss-preset-env: filter features by implementation status

[romainmenke]

Note on the size of this change :

I did not dare adding more logic to preset-env without having more granular unit tests.
This required splitting everything up into separate functions and files.

My aim was to make the entire code base more clear and easier to update with this in mind.

Some newer JS features like Symbol and Map are used to make everything a bit more predictable.

• Symbol makes it safer to combine data from multiple source (plugin options, cssdb) while still knowing which keys were set by postcss-preset-env.
• Map prevents unexpected behaviour when users set options that overlap with build-ins like toString.

This does not yet have full test coverage with unit tests alone but the combo of the new unit tests and postcss-tape should still be a step in the right direction.

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After this initial refactor it became trivial to add the minimumVendorImplementations option.

There is no overloading of this option or hidden logic around it.

minimumVendorImplementations is always converted to a number between 0 and 3.
0 is equivalent to not setting the option.

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There is still one bit of undefined logic that I haven't tracked down and added tests for.

When using insertAfter or insertBefore it is unclear if those plugins become dynamic based on the browser lists of the feature they are attached to.

I need to check this on main first.

Update :

• added tests in main and merged them into this branch
• behaviour is to always run the inserted plugins, these are not dynamic

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Notable fix :

see :

postcss-plugins/plugin-packs/postcss-preset-env/test/basic.nesting.true.expect.css

Lines 39 to 41 in e83f355

	.test-nesting-rules + p, #test-is-pseudo + p {
	order: 8;
	}

We added getOptionsForBrowsersByFeature some time ago and this had a bug.

if (features[feature.id] === true) {
	// if the plugin is enabled
	options = sharedOpts ? Object.assign({}, options, sharedOpts) : undefined;
}

When manually enabling a feature like postcss-nesting but without adding any sharedOpts the flags set by getOptionsForBrowsersByFeature would be erased. As options was set to undefined in this case.

This has been fixed.

[Antonio-Laguna]

Wow! This is really great!

Thanks for cleaning this up and making this much more manageable and sustainable in the future.

Only question I have is if you want to clarify more around the vendorImplementations as in explaining what stability usually means?

[Antonio-Laguna]

❤️