Bugfix in calculation of modified time of files in watch mode

[ryanwilsonperkin]

What kind of change does this PR introduce?

Bugfix

Did you add tests for your changes?

No, seemed too niche for a test case but happy to add one with a bit of instruction (namely whether test/plugin/plugin.test.js is the correct spot)

If relevant, did you update the documentation?

Not relevant, updates a verbose log

Summary

Fixes #3197

We need to pass the timestamp in milliseconds to the date constructor, this code was assuming that changeTime was in seconds and needed to be multiplied by 1000 to get milliseconds but it is already in milliseconds.

This led to the constructed date being incorrect.

Before	After

Does this PR introduce a breaking change?

No

Other information

It appears that the changeTime value comes through the WatchMethod value of WatchFileSystem type, ultimately tracing back to the watchpack package. Watchpack uses fs.lstat to retrieve a fs.Stat object of the file and retuns the mtime by casting it to a number using the + operand. This might cause some platform-dependant behaviour, such as if +new Date() returns different levels of precision between Mac/Windows/Linux/etc. There's a mtimeMs on the Stat object that might be more appropriate in this case to ensure a certain level of precision is returned.

Ref: https://nodejs.org/api/fs.html#stat-time-values

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: ryanwilsonperkin / name: Ryan Wilson-Perkin (4751a2d)

[codecov]

Codecov Report

Merging #3198 (4751a2d) into master (6d778a5) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #3198   +/-   ##
=======================================
  Coverage   90.98%   90.98%           
=======================================
  Files          23       23           
  Lines        1731     1731           
  Branches      519      519           
=======================================
  Hits         1575     1575           
  Misses        156      156           

Impacted Files	Coverage Δ
packages/webpack-cli/src/plugins/CLIPlugin.ts	100.00% <100.00%> (ø)

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[rishabh3112]

Looks good, lets wait for CI to be green.

[rishabh3112]

/cc @webpack/cli-team need one more review

[snitin315]

LGTM, thanks!

[rishabh3112]

Thanks