Expo-dev-client appears to not display full context for Javascript syntax errors encountered in development builds. Ideally, I'd see something like:
ERROR [SyntaxError: Unexpected identifier 'resolveAfter2Seconds'. Expected ')' to end an argument list.]
/Users/alexanderriccio/Documents/scratch_work/weird_expo_compile_issue_bare/my-app/index.js:15:13
console.log(await resolveAfter2Seconds);
~~~~~~~^
...instead, all we get is:
ERROR [SyntaxError: Unexpected identifier 'resolveAfter2Seconds'. Expected ')' to end an argument list.]
In my case, an errant top level await (console.log(await notifee.getTriggerNotifications());) that would normally show up in the expo error overlay (ErrorFragment?) somehow made it through metro compilation, and then caused hermes to fail. The development build would immediately native crash anyways, so I wouldn't know. My only clue was this line in the device system log (adb logcat):
HermesVM: Compiling JS failed: 1200:21:')' expected at end of function call, Buffer size 7031284 starts with: 766172205f5f42554e444c455f535441 and has protection mode(s): r--p
Sometimes - very rarely, like when typing this report - it would instead display that message in a "Project didn't load" screen.
I am not entirely sure how expo normally handles errors, so I'm not actually sure why this caused a native crash. Currently, my wild guess is that somewhere like in the module interop code, low level view code (also, higher up the callstack), or somewhere else entirely, is calling into evaluateJavascript and not catching the C++ exception.
I initially thought this was a hermes bug where for some reason no useful info was dumped. I was wrong, and honestly it should have been a little bit more obvious to me in retrospect, but I was confused by the fact that I'd seen no errors from metro or expo. In this case, the hermesvm output to the android system log was the only clue as to why the app was breaking. Without it, I may have been fighting for hours over a tiny mistake.
When explicitly running a release variant (npx expo run:android --device --variant release), I get the correct/reasonable output:
/Users/alexanderriccio/Documents/GitHub/COVID-CO2-tracker/co2_native_client/android/app/build/generated/assets/react/release/index.android.bundle:712:21: error: ')' expected at end of function call
console.log(await _reactNative.default.getTriggerNotifications());
~~~~~~~^