Treeshaking pure external functions

[basav22]

Hi, I am unable to understand why is dead code (AgroButtonDefault in this case). Please help me understand

Please find below repl -

https://rollupjs.org/repl?version=0.53.2&shareable=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

[guybedford]

@lukastaegert a treeshake.pureExternalFunctions = [{ id: 'styled-components', name: 'button' }] perhaps!?

[lukastaegert]

@basav22: The issue is that rollup will always assume that external functions (which includes tag functions of tagged template literals as in this example) have side-effects. Both the definitions of the "primary" and the "default" button call the function "styled.button()" - and this function is called when the module is initialised and not when the buttons are actually used.

@guybedford 's suggestion of adding an option to list pure external function sounds good to me.

Additionally, we could start supporting UglifyJS /*@__PURE__*/ annotations. There already is an issue for that (#1293) and it might be a good idea to implement this together with a complementary /*@__KEEP__*/ annotation to resolve #1771 .

In any case I would classify solving this problem as an interesting enhancement. Further suggestions are always welcome.

[lukastaegert]

I have taken the liberty to slightly adjust the issue title

[acewf]

i resolved the issue by adding { modules: false } on the babel loader present

{
   loader: 'babel-loader',
   options: {
       presets: [
            ["@babel/preset-env", { modules: false }]
       ],
   }
}

[shellscape]

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