investigate flaky test-fs-watch-file-enoent-after-deletion

[Trott]

• Version: 11.0.0-pre (master)
• Platform: win10 vs2017
• Subsystem: test

https://ci.nodejs.org/job/node-test-binary-windows/18408/COMPILED_BY=vs2017,RUNNER=win10,RUN_SUBSET=3/console

13:48:22 not ok 561 sequential/test-fs-watch-file-enoent-after-deletion
13:48:22   ---
13:48:22   duration_ms: 0.668
13:48:22   severity: fail
13:48:22   exitcode: 1
13:48:22   stack: |-
13:48:22     assert.js:80
13:48:22       throw new AssertionError(obj);
13:48:22       ^
13:48:22     
13:48:22     AssertionError [ERR_ASSERTION]: Input A expected to strictly equal input B:
13:48:22     + expected - actual
13:48:22     
13:48:22     - 0
13:48:22     + 1
13:48:22         at StatWatcher.<anonymous> (c:\workspace\node-test-binary-windows\test\sequential\test-fs-watch-file-enoent-after-deletion.js:46:10)
13:48:22         at StatWatcher.<anonymous> (c:\workspace\node-test-binary-windows\test\common\index.js:467:15)
13:48:22         at StatWatcher.emit (events.js:182:13)
13:48:22         at StatWatcher.onchange (internal/fs/watchers.js:47:8)
13:48:22   ...

[Trott]

Looks to be a race condition between watchFile() and setTimeout().

[Trott]

Reproducible if you put the call to watchFile() in a timer such that it gets executed after setTimeout().

[Trott]

(fs.watchfile() is synchronous, but probably the underlying operating system watch stuff it depends on is not?)

[Trott]

@nodejs/platform-windows @nodejs/fs @nodejs/testing

[Trott]

This has, unsurprisingly, come up before:

f1c890afb05
#13800 especially #13800 (comment)
#14010

[Trott]

OK, now I think I have a fix...

[Trott]

Hopeful fix: #21694