fix(ios): return proper mimeType on M1 x86_64 simulators

[arnold-plakolli]

In one of the projects I'm working on we are having an issue of app getting stuck on white screen in iOS simulators 14.0+ that run on M1 machines.

After much trial and error we found out that in the ios/Capacitor/Capacitor/WebViewAssetHandler.swift file, the method mimeTypeForExtension was returning default application/octet-stream value for many path extensions. In real devices or simulators with lower iOS versions, it was returning correct value.

The issue was with the object UTTypeCreatePreferredIdentifierForTag. This object was returning nil value and as a result the method was defaulting to the value application/octet-stream.

This happens for projects:

• With checked Open using Rosetta option for Xcode
• With unchecked Open using Rosetta option for Xcode
  • Forcing architecture x86_64 for simulator builds

UTTypeCreatePreferredIdentifierForTag is marked as deprecated and Xcode suggested using UTType instead. I did that but with same result as before.

I ended up providing a dictionary of path extensions and mime types. I added the dictionary as a fallback in case UTTypeCreatePreferredIdentifierForTag returns nil.

Issue environment:

• Machine: M1 Mac (Apple Silicon)
• iOS Simulator: 14.0+

Sample projects:

• Referencing version 4.0.1 of @capacitor/ios that shows blank screen: https://github.com/arnold-plakolli/BlankScreenIssueDemo
• Referencing the fixed version in this PR of @capacitor/ios that works: https://github.com/arnold-plakolli/BlankScreenFixedIssueDemo

closes #5793

[jcesarmobile]

have you tried turning off Open using Rosetta (uncheck the checkbox) and restarting the computer?
for me just unchecking the checkbox had no effect, I had to restart the computer.
Also needed to do a Product -> Clean Build Folder from Xcode before running

[arnold-plakolli]

have you tried turning off Open using Rosetta (uncheck the checkbox) and restarting the computer? for me just unchecking the checkbox had no effect, I had to restart the computer. Also needed to do a Product -> Clean Build Folder from Xcode before running

@jcesarmobile I did that for the blank Ionic project and it did work. The simulator loaded the app and it did not get stuck on the white screen.

However when I ran the project, in which I initially had this bug on, it still showed the white screen.

When I looked at the project build settings, I noticed that it was forcing architecture x86_64 for simulators and that's when UTTypeCreatePreferredIdentifierForTag returns nil.

So it seems this fix is still valid for projects:

• With checked Open using Rosetta option for Xcode
• With unchecked Open using Rosetta option for Xcode
  • Forcing architecture x86_64 for simulator builds

I'll update the PR description as well to reflect these findings.

Thanks @jcesarmobile

[jcesarmobile]

You mean the project you shared or a different project?

where is that setting for using x86_64 on simulators?

[arnold-plakolli]

@jcesarmobile

The project I originally encountered the bug on is a different project not the one I shared.

I updated the PR description that points to two sample projects which both force arch x86_64 for simulator builds. One of the projects points to version 4.0.1 of @capacitor/ios and the other one points to the fixed version in this PR. You can run them both with Open using Rosetta unchecked and you can see that the one that points to version 4.0.1 shows a blank screen. At least that's what I encountered on my tests.