[Bug] Analytics does not work on iOS if frameworks are not statically linked

[p-lindberg]

[REQUIRED] Please fill in the following fields:

• Unity editor version: 2020.3.18f1
• Firebase Unity SDK version: 8.6.0
• Source you installed the SDK: .unitypackage
• Problematic Firebase Component: Analytics
• Other Firebase Components in use: None
• Additional SDKs you are using: None
• Platform you are using the Unity editor on: Mac
• Platform you are targeting: iOS
• Scripting Runtime: IL2CPP
• Cocoapods version: 1.11.2
• Xcode version: 13.1
• MacOS version: 11.6

[REQUIRED] Please describe the issue here:

After integrating Firebase Analytics into a project I'm working on, I discovered the following issues on iOS:

• No user-defined events gets reported, whereas the auto-reported events (session_start, user_engagement, etc) work fine. By user-defined events I mean those events that I am logging using FirebaseAnalytics.LogEvent().
• FirebaseAnalytics.SetUserId and FirebaseAnalytics.SetUserProperty does not work.

The above was verified by:

• Using the DebugView in Firebase to view incoming events: only auto-reported events show up.
• Exporting all events to BigQuery and querying for distinct event names as well as user ids: only auto-reported event names are present, and all user ids are null.
• Checking the device logs while running the app in Xcode: absolutely nothing is logged by Firebase when any of the above mentioned methods are called.

I then noticed that when the app starts, about 150 warnings of the following kind are printed to the log:

objc[2852]: Class FIRAAdExposureReporter is implemented in both /private/var/containers/Bundle/Application/2FDF37A0-448E-4A64-8018-80ECA33CF1D6/Test.app/Test (0x1023d9358) and /private/var/containers/Bundle/Application/2FDF37A0-448E-4A64-8018-80ECA33CF1D6/Test.app/Frameworks/UnityFramework.framework/UnityFramework (0x1061d9c00). One of the two will be used. Which one is undefined.

I found that enabling the option "Link frameworks statically" in the EDM4U iOS Resolver fixes both the warnings and the issues with Firebase Analytics. I can see how static linking resolves the duplicate implementation issue, but I'm uncertain as to why this is necessary, since the Firebase pods are only added to the UnityFramework target in the podfile. The podfile looks like this before applying the option:

source 'https://github.com/CocoaPods/Specs.git'
platform :ios, '11.0'

target 'UnityFramework' do
  pod 'Firebase/Analytics', '8.9.1'
  pod 'Firebase/Core', '8.9.1'
end
target 'Unity-iPhone' do
end
use_frameworks!

And with "Link frameworks statically" the last line is updated to

use_frameworks! :linkage => :static

Now, I'm reporting this as a bug because the Firebase Unity SDK is ostensibly broken out-of-the-box because of this. As far as I can tell, there is no indication in any setup instructions or guides that this option needs to be enabled for things to work - and the option is disabled by default. Even worse, the SDK will build just fine and everything seems to work until you notice that your custom events do not get reported on iOS.

I have verified that the exact same result is achieved when setting up the quickstart project according to the instructions given, so this is not specific to my project.

Steps to reproduce:

• Pull the quick-start repo
• Launch the analytics testapp
• Follow the instructions to add the Firebase SDK
• Build for iOS
• Observe that auto-reported events gets logged
• Observe that custom events do not get logged
• Toggle Link frameworks statically on in iOS Resolver settings and rebuild
• Observe how everything works as expected.

[chkuang-g]

Though it is recommended to link pods statically, I think it is not a requirement.
https://firebase.google.com/docs/ios/link-firebase-static-dynamic

Perhaps something changed at iOS SDK level. Let me consult with internal team about this.

[chkuang-g]

OK. I found an internal bug (b/196153528) about this matter.

Simply put, to link pods statically by default, you will also need to generate a dummy.swift file like the following, or the Xcode project generated by Unity may not link other 3rd party libraries, ex. Facebook, properly.

import Foundation

This seems to be a feature request for EDM4U side.

On the other hand, I need to consult with iOS team to understand why dynamic linkage failed in this case.

[DaveMariner]

As an addendum - this also affects SDKs as far back as 7.1.0.

Somewhat interestingly, there's at least one of our products where everything works just fine and we're (I believe) not linking statically - at least, not through the Podfile. Got more digging to do tomorrow.

[DaveMariner]

I did some more digging. It seems that adding '-ObjC' to 'OTHER_LDFLAGS' fixes the issue. We currently do this with a [PostProcessBuild] Editor script.

@p-lindberg: If this is still an issue for you, this is our minimal standalone fix.
@chkuang-g: Is something like this suitable for EDM?

using UnityEditor;
using UnityEditor.Callbacks;
using System.IO;

#if UNITY_IOS
using UnityEditor.iOS.Xcode;
#endif

public static class PostBuild
{
    [PostProcessBuild]
    public static void OnPostprocessBuild(BuildTarget buildTarget, string path)
    {
#if UNITY_IOS
        string projPath = path + "/Unity-iPhone.xcodeproj/project.pbxproj";

        PBXProject proj = new PBXProject();
        proj.ReadFromString(File.ReadAllText(projPath));

        string target = proj.GetUnityMainTargetGuid();
        string projectGuid = proj.ProjectGuid();

        // Set a custom link flag
        proj.AddBuildProperty(target, "OTHER_LDFLAGS", "-ObjC");
        File.WriteAllText(projPath, proj.WriteToString());
#endif
    }
}

[nostek]

@DaveMariner 's solution worked for us, example code is missing a ''File.WriteAllText(projPath, proj.WriteToString());" in the end.

@p-lindberg thanks for reporting :)

[DaveMariner]

@nostek: Good catch - have added that into the example code for anyone else with the same issue. Glad it helped!