treeshake.pureExternalModules not run after terser minification.

[azizhk]

When used with treeshake.pureExternalModules, essentially all unused imports after terser minification should be removed. But I guess that happens before the minification and thus persists.

Minimal reproducing case: https://repl.it/repls/SoupyWigglyExtraction
Here it should not log anything. (The last line of index.js)

This might not be a bug with rollup-plugin-terser or rollup or terser individually per se, but maybe if we can change the order this might work.

Related: terser/terser#168 which might require some effort if tackled only from terser's side.

[bvaughn]

Looks like adding this plug-in also removes the #__PURE__ annotations from the resulting bundle (at least based on my experiments with using it in react-window)

[azizhk]

Hi @bvaughn
I think your issue is with terser. I tried a bunch of settings but could not retain the comments with just terser: https://repl.it/repls/ProudClientsideGreenware
And as this plugin is a wrapper around terser, I don't think this plugin will be able to retain the comments unless fixed in terser. Let's open an issue with terser for this.

I think you have another step for tree shaking after your code goes through terser where it is unable to treeshake because #__PURE__ comments are no longer there.

My issue is slightly different. My #__PURE__ code + comment gets removed correctly but rollup's treeshake.pureExternalModules step happens before my code is passed to terser and not after so my unused imports are still retained. (For which I am doing regex for my agadoo like tree shaking tests)

[bvaughn]

I think your issue is with terser.

Agreed.