fix(runner): fast sequential task updates missing

[AriPerkkio]

Description

• Fixes OnTestCaseReady's timing not firing as Expected #8108

The sendTasksUpdateThrottled is called sequentially with suite-prepare and test-prepare. The suite-prepare is reported to main thread immediately. The test-prepare hits throttle's limiter, and is ignored. It is reported to main thread on the next invokation of sendTasksUpdateThrottled, which is test-finished. If user's test case is taking 5000ms, the reporting of test-prepare takes 5000ms too.

As solution we'll need to make sure throttle flushes its queue even when it's not called again.

Note:

• As onUserConsoleLog is not throttled, it's still possible that reporters see test case's console logs before onTestCaseReady, if logs happen 100ms within the start.

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[hi-ogawa]

Good catch! throttle implementation by me (and copilot) was too poor 😅 #7700

I just checked tanstack's throttle implementation https://github.com/TanStack/pacer/blob/0f2cd3cfc45956dc40e6b865210c47d56f5fc129/packages/pacer/src/throttler.ts#L155 and it looks like the concept is called trailing.

Though we can maybe tweak the delay, I think throttling event timing breaking users expectation like #8108 is not completely avoidable. Maybe we can mention this in the doc?

[hi-ogawa]

If this order is flipped, then can onUserConsoleLog often appear before onTestCaseReady?

          console.log("Test running!")
          await new Promise(resolve => setTimeout(resolve, 150))

[AriPerkkio]

Yeah that's mentioned on the PR description, this part:

Note:

• As onUserConsoleLog is not throttled, it's still possible that reporters see test case's console logs before onTestCaseReady, if logs happen 100ms within the start.

So on the test runner thread side, the test case's console.log happens after test-prepare is called. It's reported to the main thread in different order since onUserConsoleLog is not handled by onTaskUpdate.