Debug Avni Client

Version compatibility (Hermes, Chrome, React Native)

React Native supports debugging via Chrome Debugger (DevTools)
Realm doesn't support debugging with JSC only with Hermes
Since Chrome keeps getting updated on our machines, so even with hermes one needs to be at a certain version for chrome debuggers for specific versions of react native (and maybe realm also).
The above problem is solved by Flipper (desktop app) which has an embedded chrome debugger - hence at fixed compatible version.
For our code, Flipper Version 0.176.0 (50.0.0) has been tested to work.

How to use

When switching the JS engine make clean_app is required. enableHermesdefault value is false.

# switch to hermes
enableHermes=true make clean_app run_app
# continue to use hermes
enableHermes=true make run_app

# switch to JSC
make clean_app run_app
# continue to use JSC
make run_app

In the make run_app log (not Metro) verify the engine by looking for [Avni] Hermes Enabled:

Flipper screenshot

If you are running JSC you will get a clear error when using the Hermes Debugger menu in Flipper. Do learn about Chrome debugger shortcuts. Command+P in sources to open a file.

Limitation

Cannot debug the errors that happen on start-up of the app as by the time one attaches the Flipper the application may have crossed the code that one may be interested in debugging.