Building Unity project with Firebase Google Analytics SDK fails: "Could not load file or assembly 'UnityEditor.iOS.Extensions.Xcode"

Question

The Problem

I am trying to integrate Firebase Google Analytics into my existing Unity project (a mobile game for iOS and Android). I was following the instructions on https://firebase.google.com/docs/unity/setup (all the prerequisites are fullfilled). Unfortunately when trying to build the Android version on Windows I get the following errors:

BadImageFormatException: Could not resolve field token 0x040000dc, due to: Could not load type of field 'Firebase.Editor.XcodeProjectModifier:projectInfoDoc' (2) due to: Could not load file or assembly 'UnityEditor.iOS.Extensions.Xcode, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' or one of its dependencies. assembly:UnityEditor.iOS.Extensions.Xcode, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null type:<unknown type> member:(null) signature:<none> assembly:C:\Users\mform\Code\guessme\Assets\Firebase\Editor\Firebase.Editor.dll type:XcodeProjectModifier member:(null) signature:<none>
System.Reflection.MonoMethod.Invoke (System.Object obj, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at <567df3e0919241ba98db88bec4c6696f>:0)
Rethrow as TargetInvocationException: Exception has been thrown by the target of an invocation.
System.Reflection.MonoMethod.Invoke (System.Object obj, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at <567df3e0919241ba98db88bec4c6696f>:0)
System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) (at <567df3e0919241ba98db88bec4c6696f>:0)
UnityEditor.Build.BuildPipelineInterfaces+AttributeCallbackWrapper.OnPostprocessBuild (UnityEditor.Build.Reporting.BuildReport report) (at C:/buildslave/unity/build/Editor/Mono/BuildPipeline/BuildPipelineInterfaces.cs:158)
UnityEditor.Build.BuildPipelineInterfaces+<OnBuildPostProcess>c__AnonStorey2.<>m__1 (UnityEditor.Build.IPostprocessBuildWithReport bpp) (at C:/buildslave/unity/build/Editor/Mono/BuildPipeline/BuildPipelineInterfaces.cs:398)
UnityEditor.Build.BuildPipelineInterfaces.InvokeCallbackInterfacesPair[T1,T2] (System.Collections.Generic.List`1[T] oneInterfaces, System.Action`1[T] invocationOne, System.Collections.Generic.List`1[T] twoInterfaces, System.Action`1[T] invocationTwo, System.Boolean exitOnFailure) (at C:/buildslave/unity/build/Editor/Mono/BuildPipeline/BuildPipelineInterfaces.cs:356)
UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr) (at C:/buildslave/unity/build/Modules/IMGUI/GUIUtility.cs:179)

Error building Player: BadImageFormatException: Could not resolve field token 0x040000dc, due to: Could not load type of field 'Firebase.Editor.XcodeProjectModifier:projectInfoDoc' (2) due to: Could not load file or assembly 'UnityEditor.iOS.Extensions.Xcode, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' or one of its dependencies. assembly:UnityEditor.iOS.Extensions.Xcode, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null type:<unknown type> member:(null) signature:<none> assembly:C:\Users\mform\Code\guessme\Assets\Firebase\Editor\Firebase.Editor.dll type:XcodeProjectModifier member:(null) signature:<none>

I don't understand why it attempts to load this assembly, which is cleary only intended for iOS anyway. And I don't know how to prevent it or get rid of this bug.

The Setup

• Windows 10 Pro
• existing Unity project with working Android/iOS builds
• Unity 2019.2.16f1
• Using the OpenJDK and Android SDK/NDK packaged with Unity
  • OpenJDK 1.8
  • Android SDK tools 29.0.2
• current dependencies (all working as expected)
  • Google Admob SDK for Unity
  • Unity Analytics
  • Unity IAP
  • Sentry
  • PlayMaker
• I added Google Analytics as described in https://firebase.google.com/docs/unity/setup
  • I completed all the steps
  • When executed in the editor the CheckAndFixDependenciesAsync continuation is called and the Firebase Dependency status is "Available"

Build Settings

Player Settings

Solution Attempts

• I reset all changes via Git and started the steps again from the start, importing the SDK unity package anew
• Using the Play Service resolver
  • I updated the Version Handler
  • I forced resolving of the Android dependencies (which works)
• deleted the Library folder and rebuild

None of these helped unfortunately. I'd be very grateful for any pointers into the right direction.

Answer 1

Thanks to a hint by @Cœur (thanks a 1000 times) I installed the iOS module in the Unity editor (even though I was only trying to build the Android version on Windows). With the iOS module installed the Android build worked.