Webpack sometimes skips modules loaded through expose-loader when tree shaking is enabled #89
Description
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
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.