snowpack build: option to not remove magic comments in dynamic imports?

[N8-B]

After doing some spelunking in the code base, I see that all comments are being stripped in dynamic imports when the source files are scanned with es-module-lexer.

I was wondering if it would be possible to restore certain comments in these dynamic imports when rewriting the imports. This is not a problem when no bundle plugin is being unused. However, if webpack is used to bundle to snowpack build output all dynamic imports with have numbers for their chunk name as all of the magic comments have been eliminated.

With v2.13.3 I have tried setting the minify and treeshake options to false, but this has no affect.

[FredKSchott]

Curious: are we doing this, or is our default "esbuild" compiler stripping them? You could add a console log inside of plugin-esbuild to confirm.

Hopefully, it's something that we're doing, so that we can fix! Otherwise, I wonder if we could do something interesting to "stitch" this back together after the fact.

[N8-B]

OK, thanks for the response. I'll have a look at what's going on in plugin-bundle and report back.

For another transformation process with es-module-lexer that we're doing in our application, we are 'stitching' the magic comments back together with the import path. Perhaps we could do the same here if plugin-bundle is not where this is happening.

[evanw]

FWIW esbuild should be preserving comments inside dynamic import() expressions since version 0.6.15: https://github.com/evanw/esbuild/blob/v0.6.15/CHANGELOG.md#0615.

[N8-B]

Ok, I'm pretty sure the issue with the magic comments is here: https://github.com/pikapkg/snowpack/blob/b21848be11041ad87656617b6b56a5084023e054/snowpack/src/rewrite-imports.ts#L36
matchDynamicImportValue strips the magic comments and the result spec is passed to the replaceImport handler.

The process begins in the buildFile method of the build command:
https://github.com/pikapkg/snowpack/blob/75ad50315d18d7d4deac0c6efc649b2b650282a8/snowpack/src/commands/build.ts#L195

I have added a local fix to add webpack's magic comments back in to the rewritten import and it works. If there is any interest in supporting this, let me know and I'll tackle it.

[FredKSchott]

100%! Thanks for finding, and happy to hear that this is something on our end. Would love a PR to fix!

[N8-B]

Done #1243