bug: CapacitorHttp XMLHttpRequest (Angular HttpClient) interceptor doesn't pass headers correctly

[dennisameling]

Bug Report

Capacitor Version

% npx cap doctor  
💊   Capacitor Doctor  💊 

Latest Dependencies:

  @capacitor/cli: 4.6.3
  @capacitor/core: 4.6.3
  @capacitor/android: 4.6.3
  @capacitor/ios: 4.6.3

Installed Dependencies:

  @capacitor/cli: 4.6.3
  @capacitor/core: 4.6.3
  @capacitor/android: 4.6.3
  @capacitor/ios: 4.6.3

[success] iOS looking great! 👌
[success] Android looking great! 👌

Platform(s)

Android and iOS

Current Behavior

When using Angular's HttpClient in combination with Capacitor's CapacitorHttp intercepting enabled, headers are sent incorrectly to the server.

Here's what it looks like on Android (did remote debugging to get some more details):

Note that the headers are a JSON-encoded string when CapacitorHttp is intercepting XMLHttpRequest. That doesn't seem right!

And here's what it looks like on iOS:

Expected Behavior

I expect Angular's HttpClient to work correctly in combination with CapacitorHttp's XMLHttpRequest interceptor.

Code Reproduction

Here's the full codebase of my screenshots above: https://github.com/dennisameling/capacitor-http-bug

Other Technical Details

npm --version output: 8.19.2

node --version output: v16.18.1

pod --version output (iOS issues only): 1.11.2

Additional Context

[matudelatower]

Same issue here, apparently overwrites all request even @angular/common/http, and interceptors doesnt work.

[jonesdhtx]

Having similar issue using fetch directly from within our capacitor project, request headers are no longer getting sent properly. Seems like this change would be the culprit: https://github.com/ionic-team/capacitor/pull/6251/files

[brandonaaron]

I'm also pointing the finger at PR #6251 for breaking http calls. App works fine in 4.6.2 but server gets bad/missing info on 4.6.3.

[muuvmuuv]

Since its Native → Browser it could be due to Access-Control-Expose-Headers. Can you try adding that to your server and select the headers you want to expose to the client?

[davy-ikv]

This change breaks passing headers in iOS

028c556#diff-73da2144bc5fefb384b6fc1501a8efbabac7cfdf2faa411b68cdd113f53d884dL430-R432

JSON.stringify headers makes headers become a String, but in native part of iOS, it expect headers is a hash table ([String: String])

[jcesarmobile]

Resolved on #6303