How to debug differences between dev app & published app?

Expo SDK
1

I’m using Expo.SQLite and a library called join-monster to store and retrieve data client-side via graphql. So far, everything works fine locally, but when I publish the Expo app (or if I eject, then do an Xcode “release build”), I get an error message that I have not been able to replicate in my dev environment.

The error message is coming from the join-monster library (https://github.com/stems/join-monster/issues/250), but the question I had for you guys: is there any way to generate the production-ified version of the app locally without actually publishing? Or instrument the published version with a debugger? If I could Debug Remote JS on the prod/buggy version of the app, I could probably figure out the root cause pretty quickly.

Here’s a minimal reproduction I just wrote using Expo/CRNA btw, https://github.com/smoll/monster

2

You could detach and build locally, then install say the .apk yourself

3

I’ve actually done this in Xcode and the “release build” manifests this bug. However, there is no way to “Debug Remote JS” inside of this app, is there?

4

Also, I was able to run idevicesyslog as described in https://docs.expo.io/versions/latest/guides/logging.html but that doesn’t make console.log statements show up, does it?

5

ya, console.log is like NSLog on iOS, so it goes to system log

6

Does the error still happen with minifcation on in dev mode?

7

@nikki Great idea, and your instinct was spot on: exp start --minify causes the error to appear!

Any ideas about what I can do next? Is the minification being performed by babel?

8

I’m going to skip minification altogether as a workaround for now. This is less than ideal, but I have to do some research into how to skip minification of specific files/code paths. This would help me narrow down whether the minification is breaking due to a problem with my code (my guess is no, since I squinted at the relatively small code for a bit and there are no obvious differences between the minified and unminified versions), or something in the join-monster package, and precisely which file/line number.

I tried using babel-preset-minify - npm to exclude things but none of the flags seem to change the minified bundle at all.