Android.Runtime.ResourceIdManager.UpdateIdValues() called multiple times, adds 23 seconds to application startup

[jalbertSyncroTech]

Description

When both an Android application and a library project include Android Resources, the Application's Resource.UpdateIdValues() is called to update all of the library project's static resource id's with the constant resource id's from the application.

This function is triggered by a call to Android.Runtime.ResourceIdManager.UpdateIdValues() in the static constructor of Resource.Designer.cs, and also by all of it's child classes eg. Drawable, Layout, etc.

The ResourceIdManager.UpdateIdValues() function has an "id_initialized" flag that's supposed to prevent the function getting called twice, however this flag isn't set until after UpdateIdValues() is complete.
https://github.com/xamarin/xamarin-android/blob/52417bdb6bf156a11a391abfc25f84cd5e18cec2/src/Mono.Android/Android.Runtime/ResourceIdManager.cs#L30

Because all of the child classes (Drawable, Layout, etc.) also call UpdateIdValues() in their static constructors, this function is triggered again each time the original call accesses one of the static child classes to update its resource id's, recursively triggering this function call again.

For example, in my Xamarin.Forms w/GooglePlay project I count this function being called 36 times during startup, for a total duration of 23 seconds, where as one call would have only taken 2 seconds.

A simple fix would be to set id_initialized to true immediately the first time the function is called, before the rest of the function is processed.

Steps to Reproduce

1. Create a solution that includes both an Android Application and a Library project.
2. Include Resources in both projects (or reference a NuGet package that includes Android Resources).
3. When debugging, put a break point on the UpdateIdValues() function in the the Application's Resource.Designer.cs file. Observe that it is called multiple times, once for each of the static children classes.

Expected Behavior

The UpdateIdValues() function in the the Application's Resource.Designer.cs file should only be called once.

Actual Behavior

The UpdateIdValues() function is unnecessarily called multiple times, adding ~23 seconds to the application startup time in the case of my project.

Basic Information

Microsoft Visual Studio Enterprise 2017
Version 15.6.5
VisualStudio.15.Release/15.6.5+27428.2027
Microsoft .NET Framework
Version 4.7.02556

Xamarin.Android SDK 8.2.0.16 (HEAD/a78295902)
Xamarin.Android Reference Assemblies and MSBuild support.

[jalbertSyncroTech]

Accidentally submitted to Xamarin.Forms originally, closed that issue
xamarin/Xamarin.Forms#2435

[jalbertSyncroTech]

Two updates:

1. This is trivially caused by using Android Resources in a library project that also references Xamarin.Forms. The first time one of those resources is accessed from that library's assembly it triggers the recursive call to UpdateIdValues(). The specific culprits are the Xamarin.Android.Support references, which add hundreds of lines to the UpdateIdValues() generated function in the Android application.

2. This appears to be related to another bug I opened Visual Studio 15.6.1 regression Android.Util.AndroidRuntimeException Activity did not call through to super.onCreate() #1399 Visual Studio 15.6.1 regression Android.Util.AndroidRuntimeException Activity did not call through to super.onCreate(). As a test I moved all of our solution's Android Resources into the application project which in addition to removing the 23s startup hit also fixed the super.onCreate() exception.

[jonathanpeppers]

@jalbertSyncroTech I apologize no one has looked at this, this seems pretty bad...

I can repro with VS 2017 15.7.4.