Watch-run doesn't update correctly

[Zn4rK]

This issue is born from cevek/ttypescript#86. This comment in particular describes the problem a bit better: cevek/ttypescript#86 (comment)

It's not caused by some internal order that I wrote there.

Expected Behaviour

I expect that files that I've changed is updated correctly.

Steps to Reproduce the Problem

I've not managed to reliably reproduce this with the testing strategy that ts-loader uses.

Location of a Minimal Repository that Demonstrates the Issue.

Clone https://github.com/Zn4rK/ttypescript-repro

Run npm run start:webpack

---

So, this is a strange one. I've spent some time trying to understand what's happening.

Looking at the source for watch-run:

ts-loader/src/watch-run.ts

Lines 20 to 21 in a43736e

	date > (lastTimes.get(filePath) || startTime) &&
	filePath.match(constants.tsTsxJsJsxRegex) !== null

It basically says: If date is more than the lastTime AND filePath is a tsTsxJsJsx file, skip.

For modified files, date will always be more than the last time.

Looking at one of the tests that fails if I change the if-statement, I would argue that the current result is wrong.

If I understand the test suite correctly, we should see something along the lines of:

TS2322: Type '"foobar"' is not assignable to type 'boolean'.

In patch1/output.txt but right now that doesn't happen. There is no expected outputs for either patch0 or patch1.

There are a few more tests that has inconsistent results with what I would assume should be happening.

My suggestion is simply to change the first for-loop to:

    for (const [filePath, date] of times) {
      const lastTime = lastTimes.get(filePath) || startTime;

      if (date <= lastTime) {
        continue;
      }

      lastTimes.set(filePath, date);
      updateFile(instance, filePath);
    }

Which seems to fix my original issue, and get the expected test results for (some of) the existing tests as well. I don't really understand how the comparison tests works with the _WatchAPI syntax.

I've removed the match for tsTsxJsJsx files completely, because I don't think that the check was intentional.