tsconfig.json extends field node-style resolution broken

[achingbrain]

Bug Report

The docs say (emphasis mine):

The value of extends is a string which contains a path to another configuration file to inherit from. The path may use Node.js style resolution.

This worked up until recently but is currently broken. I can't pin down a specific version where it stopped working as I guess the code that loads the config may be from a dependency of typescript that is shared across different versions.

We've got a module that contains org-wide tsconfig that we want our projects to extend - they could be regular modules, monorepo packages, etc.

Those projects can and do get pulled in as github urls (or https://gitpkg.now.sh/ urls for monorepo packages) for other modules as dependencies during PRs. Those projects are typically written in js but generate types from jsdoc comments using the npm prepare script for the current module to use, which now fails as it can't resolve the extends path.

You can't always predict which node_modules folder will contain the relevant dependency, so doing Node.js style resolution (e.g. stepping up through directories) is essential for our use-case.

🔎 Search Terms

• tsconfig extending npm package
• tsconfig extend node_modules
• tsconfig node_modules
• tsconfig extend resolve

🕗 Version & Regression Information

Not sure, it was working before Christmas, now it does not.

🙁 Actual behavior

Typescript does not resolve the extends path using Node.js style resolution.

🙂 Expected behavior

Typescript should resolve the extends path using Node.js style resolution.

References:

#18865
#30701

[RyanCavanaugh]

Please include a setup that reproduces the problem.

[achingbrain]

I think I've figured out what's happening.

The shared config is in the aegir module under src/config/tsconfig.aegir.json.

It's specified in extending tsconfig.json files as:

{
  "extends": "aegir/src/config/tsconfig.aegir.json",  <-- does not work
  // .. other stuff
}

Or alternatively:

{
  "extends": "./node_modules/aegir/src/config/tsconfig.aegir.json",  <-- works
  // .. other stuff
}

Aegir uses typesVersions in it's package.json to direct tsc to the ./dist folder where the generated types are published:

"typesVersions": {
  "*": {
    "utils/*": [
      "dist/utils/*"
    ],
    "src/*": [
      "dist/src/*",
      "dist/src/*/index"
    ],
    "src/": [
      "dist/src/index"
    ]
  }
}

The tsconfig file is not copied to dist during building but it looks like tsc is using the typesVersions field to override where it loads the config file from.

If I copy the config file into dist/src/config or if I modify the typesVersions field as below it starts to work:

"typesVersions": {
  // .. other fields
  "src/config/tsconfig.aegir.json": [
    "src/config/tsconfig.aegir.json"
  ]
}

Which I guess is fair enough, I can see why you might want different config files for different ts versions, though the docs only mention loading .d.ts files from locations specified in typesVersions.

[RyanCavanaugh]

The interaction here wasn't really intentional to be honest, but in retrospect is needed -- compiler options in tsconfig doesn't allow extra properties, so if you used a setting from a newer version of TS you'd have to set up typesVersions. We should add this to the docs, somewhere.

[achingbrain]

Ok, feel free to close this issue if it's not useful keeping open, my problem is resolved.