fix(index): copy loader options before modifying

[clydin]

As per the loader-utils documentation (here), the options object should not be modified directly. Doing so causes the loader parameter of a plugins option function to only be run once at the first use of the loader. This effectively causes the loader parameter to be useless as it cannot be used to retrieve information about the actual resource being used (i.e., loader.resourcePath, etc.) instead it will always point to the first resource the loader handled. This PR makes a copy of the options object returned from getOptions.

Type

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• Fix

SemVer

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• Bug (:label: Patch)

Issues

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Checklist

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• Lint and unit tests pass with my changes
• I have added tests that prove my fix is effective/works
• I have added necessary documentation (if appropriate)
• Any dependent changes are merged and published in downstream modules

[coveralls]

Coverage increased (+0.5%) to 87.333% when pulling 3d1f59a on clydin:clone-options into b9c1add on postcss:master.

[michael-ciniawsky]

@clydin Thx

[michael-ciniawsky]

😅 👍

[michael-ciniawsky]

@clydin Did you test with postcss.config.js aswell ? This shouldn't be an issue here I assume...
Can you give an small usage example where this is reproducible ? (When exactly does this cause undesired behavior/breaks ?)

[clydin]

The issue stems from this line which is modifying the options object: https://github.com/postcss/postcss-loader/blob/master/lib/options.js#L5

Since that line changes the plugins property value from the function to the returned array and that options object is still used and kept by webpack, the function will never be called again as the plugins property is now an array for the rest of the webpack compilation. This essentially captures the passed in loader context object inside the returned plugins array. So the example in the readme (https://github.com/postcss/postcss-loader#plugins) for accessing loader.resourcePath only works for the first resource loaded. Every subsequent file processed with the loader will have the same first loader.resourcePath.

[michael-ciniawsky]

Released in v2.0.10 🎉 Thx