tsc watch bug

This repo is a minimal reproduction of what seems to be a bug with the TypeScript compiler's watch mode. For some reason, this particular set of dependencies in package.json causes tsc to watch files that aren't targeted for compilation.

I submitted an issue that references this repo.

2018-04-28 update: One of the TypeScript developers looked into it and replied with an explanation of the behavior. The root directory is watched in case new files are added, and there is a cap of 250 files for TypeScript to check if files actually affect module resolution. So removing a dependency in this repo fixes the issue because it reduces the number of files to below that limit.

Reproduction steps

1. I used Node v8.6.0, Yarn v1.5.1, and TypeScript v2.8.1.
2. Clone this repo, and run yarn install.
3. Run yarn tsc -w or yarn tsc -w src/foo.ts. The bug should occur either way.
4. Make a change in package.json, bar.js, or node_modules/ioredis/index.js, and save.
5. tsc should update with: File change detected. Starting incremental compilation...

Comments

1. tsc seems to process the type definitions in node_modules, even though foo.ts doesn't import any package. This behavior was surprising to me.
2. I originally ran into this issue in a project repo. I attempted to trim down the dependencies to a single offending one, but it seems like something about this combination is not good. Removing any more dependencies fixed the issue during my testing.
3. I tried using typescript@next, but the issue still occurs.