Loading Ultra module from local folder: DevTools source maps not working

[d9k]

Tried to fork Ultra to fix JSON import crash on client side | ultra Issue #288

At importMap.json I set

  "ultra/": "file:///home/d9k/forks/ultra/"

Then run deno task dev from my project code folder as usual. It works but browser DevTools sources maps stopped to work (no top/localhost:8000/_ultra/compiler folder and files from there available)!

I have Ultra fork folder at v2.3.8 git tag without any code changes.

Before and after switch "ultra/" in importMap.json from https://deno.land/x/ultra@v2.3.8/ to local folder

How to fix browser DevTools source maps when mapping Ultra module dependency to local folder?

[d9k]

Strangely DevTools source mapping works if I change importMap.json entry to relative path:

  "ultra/": "../../../forks/ultra/"