react-native: Unable to debug new Hermes React Native app using Chrome DevTools

Description

I’m unable to debug a new React Native app that’s using Hermes by following the Hermes debugging instructions found here: https://reactnative.dev/docs/hermes#debugging-js-on-hermes-using-google-chromes-devtools

Upon following those steps and opening the console in the stand alone Chrome DevTools, I see this error:

DevTools failed to load source map: Could not load content for http://localhost:8081/index.map?platform=ios&dev=true&minify=false&modulesOnly=false&runModule=true&app=org.reactjs.native.example.tempRN0710RC3: Fetch through target failed: Cannot read properties of null (reading 'loadNetworkResource'); Fallback: Unknown error

Nothing shows up in the Sources tab. Navigating to that URL outside of the dev tools does load the source map file successfully.

I am able to debug successfully using Flipper - source maps seem to load fine there.

Version

0.71.0-rc.3

Output of `npx react-native info`

info Fetching system and libraries information...
System:
    OS: macOS 12.6.1
    CPU: (10) arm64 Apple M1 Pro
    Memory: 2.67 GB / 32.00 GB
    Shell: 5.8.1 - /bin/zsh
  Binaries:
    Node: 16.13.0 - ~/.nvm/versions/node/v16.13.0/bin/node
    Yarn: 1.22.17 - ~/.nvm/versions/node/v16.13.0/bin/yarn
    npm: 8.1.0 - ~/.nvm/versions/node/v16.13.0/bin/npm
    Watchman: 2022.03.21.00 - /opt/homebrew/bin/watchman
  Managers:
    CocoaPods: 1.11.3 - /opt/homebrew/bin/pod
  SDKs:
    iOS SDK:
      Platforms: DriverKit 22.1, iOS 16.1, macOS 13.0, tvOS 16.1, watchOS 9.1
    Android SDK: Not Found
  IDEs:
    Android Studio: 2021.2 AI-212.5712.43.2112.8609683
    Xcode: 14.1/14B47b - /usr/bin/xcodebuild
  Languages:
    Java: 18.0.1.1 - /usr/bin/javac
  npmPackages:
    @react-native-community/cli: Not Found
    react: 18.2.0 => 18.2.0 
    react-native: 0.71.0-rc.3 => 0.71.0-rc.3 
    react-native-macos: Not Found
  npmGlobalPackages:
    *react-native*: Not Found

Steps to reproduce

Create a new React Native project using the command: npx react-native init RN0710RC3 --version 0.71.0-rc.3
Once created, cd in to project directory. Run using yarn ios or yarn android
Follow steps outlined in Hermes debugging documentation: https://reactnative.dev/docs/hermes#debugging-js-on-hermes-using-google-chromes-devtools
Notice source maps don’t load, unable to set breakpoints.

Snack, code example, screenshot, or link to a repository

No code example since it’s reproducible using a new RN 70 or 71 project: npx react-native init RN0710RC3 --version 0.71.0-rc.3

About this issue

Original URL
State: open
Created 2 years ago
Reactions: 20
Comments: 38 (1 by maintainers)

Most upvoted comments

The state of debugging RN has been a difficult one from the beginning. Most developers use console.log to “debug” to this day. There is no integration into VScode (which has an excellent debugger) and hermes does not improve a lot in that regard. I wonder if there are any devs out there who managed to get debugging working (consistently)?

+21

pke on Apr 27, 2023

Recent versions of Chrome have stopped fetching sources from URLs in this scenario. We have an upcoming fix that will restore this functionality (by fetching the source directly, instead of via a URL). In the meantime, the easiest way to restore source loading is by using a previous version of Chrome, or Flipper.

We can’t use flipper in our case as it’s not compatible with react-native-firebase. So this issue is quite a show-stopper for our react-native upgrade initiative.

Any suggestions over how source map could be added manually? Thanks.

+20

hishammalik on Dec 30, 2022

Just thought I’d add my two cents. This is also happening for me on 0.71.2 and Chrome Version 110.0.5481.77. Console doesn’t show logs and files don’t show up in Sources. Actually, they’ve never showed up in Sources, but I could definitely use the Console before. Also using react-native-firebase so cannot use Flipper. Hoping for some guidance soon, thank you!

gabriellend on Feb 15, 2023

Recent versions of Chrome have stopped fetching sources from URLs in this scenario. We have an upcoming fix that will restore this functionality (by fetching the source directly, instead of via a URL). In the meantime, the easiest way to restore source loading is by using a previous version of Chrome, or Flipper.

mattbfb on Dec 9, 2022

Any updates?

HoangTrongKhanh on Nov 3, 2023

I’m experiencing the same issue with react-native:0.71.12 on IOS. Subscribing…

Barrakkuda on Jul 22, 2023

anyone knows if this is getting adressed in v0.72 ? On Android I can debug with Hermes enabled, and it is actually a lot better in terms of performance debugging Android with Hermes, we just need to be able to debug on ios (we cant use flipper on our project)

Lakston on Jun 7, 2023

a temporary workaround is to disable the js source maps option in the devtool 😵‍💫

nguyenthetoan on Mar 17, 2023

same issue. devtools didnt work https://reactnative.dev/docs/hermes#debugging-js-on-hermes-using-google-chromes-devtools

itsmeshusha on Feb 7, 2023

I had to temporarily disable Hermes in Podfile :hermes_enabled => false, for debug mode to be able to use react-native-debugger. Any other workarounds?

hpelitebook745G2 on Apr 3, 2023

I’m seeing a similar issue with react-native-debugger and RN v0.71

bcsaxon on Feb 6, 2023

I’m still seeing this issue with react native v0.71.1 and Chrome 109.0.5414.119

wadeww on Jan 25, 2023

I’m also seeing the same issue as @benrbrook with react native v0.71.1 and Chrome 109.0.5414.119

robincwillis on Jan 28, 2023

It seems like this should have been fixed in the latest 0.71 release.

By loading source maps over the network with Metro we’ve restored the ability to use source maps in recent versions of Chrome Dev Tools outside of Flipper.

https://reactnative.dev/blog/2023/01/12/version-071#hermes

However, I’m still not able to load source maps with the same error as above: DevTools failed to load source map: Could not load content for http://localhost:8081/index.map?platform=ios&dev=true&minify=false&modulesOnly=false&runModule=true&app=appname: Fetch through target failed: Cannot read properties of null (reading 'loadNetworkResource'); Fallback: Unknown error

Any ideas on how to get around this or if it’s still an outstanding issue? Thanks!

System:
    OS: macOS 13.1
    CPU: (8) x64 Intel(R) Core(TM) i5-8259U CPU @ 2.30GHz
    Memory: 27.85 MB / 16.00 GB
    Shell: 5.8.1 - /bin/zsh
  Binaries:
    Node: 19.1.0 - /usr/local/bin/node
    Yarn: 1.22.19 - ~/project-name/node_modules/.bin/yarn
    npm: 8.19.3 - /usr/local/bin/npm
    Watchman: Not Found
  Managers:
    CocoaPods: 1.11.3 - /Users/bbrook/.rbenv/shims/pod
  SDKs:
    iOS SDK:
      Platforms: DriverKit 22.1, iOS 16.1, macOS 13.0, tvOS 16.1, watchOS 9.1
    Android SDK: Not Found
  IDEs:
    Android Studio: Not Found
    Xcode: 14.1/14B47b - /usr/bin/xcodebuild
  Languages:
    Java: 16.0.1 - /usr/bin/javac
  npmPackages:
    @react-native-community/cli: Not Found
    react: 18.2.0 => 18.2.0 
    react-native: 0.71.1 => 0.71.1 
    react-native-macos: Not Found
  npmGlobalPackages:
    *react-native*: Not Found

benrbrook on Jan 20, 2023

@jkoutavas Failed to create a new MMKV instance: React Native is not running on-device. MMKV can only be used when synchronous method invocations (JSI) are possible. If you are using a remote debugger (e.g. Chrome), switch to an on-device debugger (e.g. Flipper) instead.

JsonKit on Dec 15, 2023

@matthewmturner I was able to get the debugger to work when following those instructions, but only when running from XCode. We are also using Firebase.

dnelsonlivecurrence on Mar 14, 2023