Reload the application once so first-run breakpoints are hit

[Matteo Boetti (teoboetti)]

Breakpoints set before the first run of a reactnativedirect session are never hit. Reloading the app by hand makes the same breakpoints work, which is the workaround users land on today.

Cause

A launch installs and starts the app, which finishes evaluating its bundle well before the CDP proxy manages to attach. Hermes replays Debugger.scriptParsed on Debugger.enable, so breakpoints registered for that first run resolve and look bound in the UI — but the code they belong to has already executed, so nothing stops.

There is no pause-on-load to wait for. Hermes answers Runtime.runIfWaitingForDebugger with:

{"error":{"code":-32601,"message":"Unsupported method 'Runtime.runIfWaitingForDebugger'"},"id":1}

so the only lever is to run the bundle again once the debugger is ready.

Change

HermesCDPMessageHandler sends a single Page.reload after the debugger goes quiet following its initial Debugger.setBreakpointByUrl / Debugger.setBreakpoint requests (300 ms debounce, once per session, cancelled on close).

Reloads are driven by the device — the nativePageReloads capability reported in /json/list — so the debugger stays attached across the reload and the breakpoints re-bind. Verified against a live RN 0.87.1 iOS target:

Page.reload → {"result":{},"id":2}

The request is sent out of band with an id the debugger never issued, so js-debug discards the reply via the unknown-response-id path in _processResponse rather than mis-attributing it.

If no breakpoints are set at launch, no reload is sent.

Validation

• tsc --noEmit clean, gulp lint reports no new warnings
• npm test — 465 passing, 0 failing (run npx gulp first, otherwise the commandsRegistered test fails on a missing dist/rn-extension)
• 5 new unit tests in test/cdp-proxy/hermesCDPMessageHandler.test.ts: reload fires, a burst coalesces into one, no second reload per session, cancelled on disconnect, breakpoint passthrough unaffected
• Manually verified end to end on React Native 0.87.1, iOS simulator, Hermes

Note

Independent of #2782 and touches no files in common, but in practice both are needed on RN >= 0.76: without #2782 the proxy never connects at all, so there is no session in which this reload could help.

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[Matteo Boetti (teoboetti)]

Closing for now — moving this to my own fork while I run it against more projects. Happy to reopen once it has more mileage.