Fix reload hang after debugger break and continue

[aeulitz]

Summary

When using Hermes and direct debugging, creating a new React instance within the same process hangs when the previous instance was broken into and continued with a debugger (see test Test Plan section below for repro steps). This problem is tracked by issue 9662 in the react-native-windows repo.

In coarse strokes, the following code actions lead to the problem:

1. During the creation of the first React instance, the lambda in ConnectionDemux::addPage creates a LocalConnection object that adds a page title into the inspectedContexts_ set (a singleton within the process).
2. React instance teardown does not clean up the inspectedContexts_ set.
3. Upon creating the second React instance, ConnectionDemux::enableDebugging sets waitForDebugger to true because it still finds the same title in the inspectedContexts_ set.
4. waitForDebugger being true results in the creation of a PausedWaitEnable FSM state that hangs the Hermes VM here.

The change proposed here causes the inspectedContexts_ set to get cleaned up on instance teardown, thus resulting in the creation of the proper FSM starting state for the second React instance in the process.

Changelog

[General] [Fixed] - Fix reload hang after debugger break and continue

Test Plan

Repro Steps

The following repro steps involve the Playground app from the react-native-windows repo. This is only illustrative; the same problem should occur with any RN host.

1. Start Metro bundler in packages/playground folder.
2. Start Playground app. Adjust settings to use Hermes and direct debugging.
3. Select a package from the package dropdown and press the "Load" button.
4. Start Chrome and navigate to chrome://inspect. Wait a few seconds if necessary, then select "Hermes React Native" from the list of debug targets.
5. In the Chrome Inspector window, break script execution via the "Break" button.
6. Resume script execution via the "Play" button.
7. In the Playground app, select the same or another package, then press the "Load" button.

Result: Playground app hangs while displaying "Loading bundle" banner. Note that script execution cannot be resumed via the Chrome Inspector as step 6. above has already switched the debugger frontend into a "running" state.

With the change proposed here, step 7. does not hang (package reloads and executes). I've added an automated test for this scenario in the react-native-windows scenario (https://github.com/aeulitz/react-native-windows/blob/DebugHang2/packages/debug-test/DebuggingFeatures.test.ts#L245))

[analysis-bot]

Platform	Engine	Arch	Size (bytes)	Diff
android	hermes	arm64-v8a	7,834,578	+268
android	hermes	armeabi-v7a	7,225,189	+378
android	hermes	x86	8,146,099	+452
android	hermes	x86_64	8,125,621	+276
android	jsc	arm64-v8a	9,712,584	-35
android	jsc	armeabi-v7a	8,465,639	-37
android	jsc	x86	9,661,679	-18
android	jsc	x86_64	10,261,065	-16

Base commit: 2e64900
Branch: main

[analysis-bot]

Platform	Engine	Arch	Size (bytes)	Diff
ios	-	universal	n/a	--

Base commit: c687dd3
Branch: main

[facebook-github-bot]

@javache has imported this pull request. If you are a Meta employee, you can view this diff on Phabricator.

[chrisglein]

FYI tracking issue on RNW repo is microsoft/react-native-windows#10370.
When this gets merged that issue can be unblocked to remove the fork and closed out.

[react-native-bot]

This pull request was successfully merged by @aeulitz in 60e7eb4.

^{When will my fix make it into a release? | Upcoming Releases}