🚀 [all] Use modular import on macOS

[cbenhagen]

Using modular imports was added in #13400 and reverted for macOS in #16773. @russellwheatley, can you share why this was done or what issues you encountered with the modular imports on macOS? Hopefully @ncooke3 can help us fix those.

[SelaseKay]

cc @russellwheatley

[russellwheatley]

@cbenhagen - Modular headers are still there for auth iOS/macOS. Could you be more specific about what you want to be added back or even what you want and what problem it solves for you?

[cbenhagen]

@russellwheatley thanks for the quick reply!

#16773 changed the imports back to umbrella headers on macOS. For example here:

• PigeonParser.h

This makes it necessary to use forward declarations in the firebase-ios-sdk when enabling TOTP and SMS MFA. For example:

• FIRTOTPSecret.h

This one forward declaration would work for TOTP. But I'd rather find a solution as for SMS MFA it gets a lot trickier.

You must have had your reasons not to use modular imports and I hope to learn from them so we can find a solution. I tried to remove the conditional import and use modules everywhere needed but was unable to find a way to make it work so far.

[russellwheatley]

Ah, I see. It was a while ago so I couldn't tell you exactly the reason, but I'm pretty sure it was related to getting SPM & cocoapod builds working for macOS. If you're able to get modular headers working for macOS, I'd happily take a look at the PR /merge. There is no hard requirement for using import directives other than ensuring both build strategies worked.

Edit - looking at the PR you linked: firebase/firebase-ios-sdk#15112 (comment)

The "module not found" was probably the reason why we couldn't use modular headers for macOS.

[cbenhagen]

Yes, it seemed like a workaround for that problem I experienced. I analyzed the differences between the iOS and macOS builds but couldn't find a way to make it work so far. A simple ObjC demo project was able to compile without issues on both platforms with modular imports.

Any ideas welcome...