tsc-watch-extends-repro

This repo provides a reproduction of a bug with tsc where it fails to pick up changes to a file referenced by extends from a tsconfig.json.

Steps

0. Install typescript with npm install

1. Start watching project

Ensure root.json has compilerOptions.strict set to true, then npm run watch to start tsc -w for this tsconfig.json.

2. Save tsconfig.json w/o changes

While watching the project, saving the tsconfig.json file should trigger tsc to detect a file change. It should still find one error:

File change detected. Starting incremental compilation...
index.ts:1:7 - error TS2322: Type 'null' is not assignable to type 'number'.

1 const x: number = null;
        ~

Found 1 error. Watching for file changes.

3. Change root.json, observe bug

Change root.json such that compilerOptions.strict is false. This also disables strictNullChecks and as such should not report the above as an error. Changing this file will not trigger a file change for the project watcher.

If you then save tsconfig.json (still without changes) it will now pick up the latest version of root.json and will no longer report any errors.

File change detected. Starting incremental compilation...

Found 0 errors. Watching for file changes.