TypeScript 4.7 source map file extension mismatch

Bug Report

🔎 Search Terms

source map, extension

🕗 Version & Regression Information

TypeScript 4.7.2

⏯ Playground Link

Not a Playground link, but the repro is here: https://github.com/unional/tersify/tree/webpack

To repro it, run yarn bundle and open the demo.html in browser.

You can see that the source-map-loader able to get the unpartial/ts/index.ts file, but not the files it referenced (./required.js, ./unpartial.js).

This is because the files are actually in TS. i.e. required.ts and unpartial.ts.

I’m not sure if this is a TypeScript 4.7 bug or source-map-loader needs to be updated to support this. But given it was working prior to TypeScript 4.7 and JS in general, it is likely that the sourcemap generated by TypeScript 4.7 needs some adjustments.

💻 Code

The referenced code unpartial is here: https://github.com/unional/unpartial It is build with sourceMap: true in tsconfig.json

Since this is related to how the code is build and consumed, I don’t have a minimal repro for this. But the library I chose to demo this are simple enough that should be simple enough.

🙁 Actual behavior

Unable to consume the source map generated by TypeScript library using TS 4.7

🙂 Expected behavior

Should work, as shown in this branch: https://github.com/unional/tersify/tree/webpack-old

[arendjr]

This seems to be another unintended consequence of the fact that TypeScript does not rewrite extensions to source files for you. #49083 is asking for a change in this behavior.

[unional]

I’m not clear on what you are saying is broken here

Please follow the steps and description above:

To repro it, run yarn bundle and open the demo.html in browser.

You can see that the source-map-loader able to get the unpartial/ts/index.ts file, but not the files it referenced (./required.js, ./unpartial.js).

The bottom line is, the source-map generated by TypeScript works in one way, does not in another. TypeScript transpile code to JavaScript. and that’s we get distributed, along with its source map.

When consuming a package, written in TypeScript or not, the source map should work. The fact that it was written in TypeScript should be out of the picture.