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Expose Loader

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Webpack sometimes skips modules loaded through expose-loader when tree shaking is enabled

flut1 opened this issue · comments

commented

I wasn't sure if this issue should be reported in expose-loader or webpack itself. Please let me know if I should report it elsewhere.

  • Operating System: Windows
  • Node Version: 11.15.0
  • NPM Version: 6.9.0
  • webpack Version: 4.35.0
  • expose-loader Version: 0.7.5

This issue is for a:

  • bug
  • feature request
  • modification request

Code

I ran into this issue while trying to expose the styled-components library as a global variable:

import 'expose-loader?styled!styled-components';
webpack.config.js

https://raw.githubusercontent.com/flut1/reproduction-expose-loader-optimization/master/with-expose-loader/webpack.config.js

Expected Behavior

styled-component is bundled and exposed as a global styled variable.

Actual Behavior

styled-component is not included in the output bundle, neither is the styled variable declaration. They are stripped out because of the { sideEffects: false } tree shaking setting in Webpack (default under { mode: 'production' }).

See the build output here.

How Do We Reproduce?

I created a minimal reproduction repository here:
https://github.com/flut1/reproduction-expose-loader-optimization

The bug reproduction can be found in the with-expose-loader directory, but I also added a variant without expose-loader and one without sideEffects: false, both of which do produce the expected output. I committed the build output for each so you don't have to clone the repository to inspect it. Additional information can be found in the repository readme.

PS: I'm not 100% sure if this is technically speaking a bug. I'm assuming that exposing a module as a global should count as "using the export" and should therefore not be stripped from output.

commented

This issue is still present on the latest version of 1.0.1. Following @flut1's findings, I'm also unsure whether webpack or expose-loader are the real problem here.
To re-test this issue, I have updated @flut1's reproduction repository, to now include the latest version and the latest builds.

This is the build output of the with-expose-loader version of the test: https://github.com/psimk/reproduction-expose-loader-optimization/blob/master/with-expose-loader/build/main.js.

And this is the whole reproduction repository: https://github.com/psimk/reproduction-expose-loader-optimization

Please let me know, if I should create a separate issue for this.

commented

Yes, please create separate issue