TS files outside project dir not being parsed -- `microbundle` uses outdated version of rpt2

What happens and why it is wrong

Environment

TS files outside the project directory being parsed as Flow files instead of TS

SyntaxError: /absolute/path/to/file.ts: Support for the experimental syntax 'flow' isn't currently enabled (2:8):

I am experiencing this when using microbundle to bundle my monorepo projects/packages

Original issue: https://github.com/developit/microbundle/issues/808

Repro: https://github.com/icaro-capobianco/bundle-bug-repro

[icaro-capobianco]

Thank you so much @agilgur5, you inspired me today! Hope to collaborate again in the future.

[agilgur5]

Got it to work

Can see my fork and read through the detailed commit log to understand it, but I’ll summarize here too.

microbundle uses an outdated version of rpt2

microbundle is using an older version of rpt2 from ~1.5 years ago, 0.29.0. Notably, 0.30.0 updated the @rollup/pluginutils dep to v4, which contains a breaking change in https://github.com/rollup/plugins/pull/517. With that change to filter, it now resolves files outside of the cwd.

I’ll report downstream to the microbundle folks that they should probably update to fix some issues like these.

empty chunk

With the pnpm override added, rpt2 resolves the file correctly and there is no error anymore… but it produces an empty chunk! But rpt2 does actually transform the code properly; here’s the output of some logs I added on this line 🤔 :

rpt2: transformResult: '{"code":"export * from 'bundle-bug-repro/modules/code';\r\n","map":{"mappings":""}}'

That was pretty perplexing for a while, but it turns out that’s actually correct behavior though because Rollup applies treeshaking and the export does nothing. This is because export * from ... actually doesn’t include the default export, and hence it is empty and treeshaken. I changed this to export { default } from ... and then it outputs a correct non-empty file 😉

workaround in older rpt2 exists too, setting rootDir

The older rpt2 that microbundle uses has a workaround for this too, using rootDir as was implemented in #249. I confirmed that this works in your repo when you add "rootDir": "../../" to some-package’s tsconfig.json.

Notably, in my last comment I couldn’t get this to work for some reason… but that’s actually because I made a coding error while modifying the local rpt2 😅 (I didn’t add braces to a previously one-line conditional when I added logging to it and completely broke the transform hook as such). Project references don’t quite work in this version, but I think that’s because https://github.com/rollup/plugins/pull/517 fixes absolute paths as well, so that’s probably due to the older version too.