tsc --watch gives diagnostic if file renamed

[ghost]

TypeScript Version: 2.7.0-dev.20171112
Tested on Linux Mint 18.

Code

Create a project with a tsconfig.json of just {} and an empty file src/a.ts.
Run tsc --watch.
Rename a.ts to b.ts.

Expected behavior:

No error.

Actual behavior:

error TS6053: File '/home/andy/sample/ts/src/a.ts' not found.

CC @sheetalkamat

[sheetalkamat]

@Andy-MS can you please tryout drop from PR #21243 which adds multiple options using environment variables TSC_WATCHFILE and TSC_WATCHDIRECTORY. The drop is built and shared at localBuilt.zip

The different options are explained in #21243 (comment) . Experience and feedback about these options is appreciated and would help us make decision on which strategy to go as default.

[ghost]

I tried it out and that fixes this issue with the default settings.
Could you add a warning if the option passed to TSC_WATCHFILE or TSC_WATCHDIRECTORY is invalid? Hard to tell if trying to set those is making any difference.