How are we going to handle _AndroidNativeLibraryForFastDev in the .net 6 world? This is used when we fast deploy most native libraries to the override directory rather than include them in the apk.

Hopefully some test will fail here, as this was removed for .NET 6:

<_AndroidNativeLibraryForFastDev Condition=" '$(_InstantRunEnabled)' == 'True' And '$(AndroidUseDebugRuntime)' == 'True' And '$(_AndroidCheckedBuild)' == '' " Include="%(_TargetLibDir.Identity)\libxamarin-debug-app-helper.so" />

I'll need to add an equivalent for these.

libxamarin-debug-app-helper.so is in our runtime packs and will end up as a @(FrameworkNativeLibrary), and those items aren't fast deployed. Before fb727f0, these files were hard coded in the <BuildApk/> task.

It looks like only @(AndroidNativeLibrary) items are added to @(_AndroidNativeLibraryForFastDev): https://github.com/xamarin/monodroid/blob/27736a7ffc48d606ab45598f761e873f8572f46a/tools/msbuild/Xamarin.Android.Common.Debugging.targets#L224.

Maybe we should look at fast deploying @(FrameworkNativeLibrary) in a future PR? If we try to fast deploy both customer libs and framework libs we'll need to rework: https://github.com/xamarin/xamarin-android/blob/aaa37c3df94490ee9befb8381f4dd7aa18226355/src/Xamarin.Android.Build.Tasks/Tasks/BuildApk.cs#L589

As for the three $(_AndroidNativeLibraryForFastDev) items explicitly mentioned here, two files are used for native static code analysis (which I don't think we ever need to put into customer apps). The other one is for the interpreter, and I am not sure if that is available in .NET 6? I am not sure if we need to worry about any of these in a .NET 6 context?

certain native libs still need to be in the apk even when fast deploying. specifically monodroid.so and its immediate dependencies. This is because it is loaded as part of the runtime startup. So we can't just fast dev everything.

The latest changes shouldn't change the current logic for .NET 6, except the block:

<!-- HACK remove any unexpected runtime components -->
<FrameworkNativeLibrary
    Remove="@(ResolvedFileToPublish)"
    Condition="  $([System.Text.RegularExpressions.Regex]::IsMatch('%(FullPath)', '.*linux-.*'))  "
/>

Instead of silently ignoring, you get a XA4301 warning now.

The tests we have for Fast Deployment should be passing, so I don't think there is actually anything broken?

This message isn't actionable; what should the user do to fix this?

For that matter, what's it mean? This reads like two separate bits of information: we can't determine the ABI, a'la "normal" XA4301_ABI, in which case the library needs to be moved into a different directory (?), but what's that have to do with RuntimeIdentifier?

This message isn't actionable; what should the user do to fix this?

I don't think there is much they can do? I could log the name of the NuGet package it came from, and suggest they remove it?

See details here: dotnet/runtime#45927

Basically, if you add a NuGet package that is missing android-* RID for native libraries, the dotnet/sdk will potentially fall back to including linux-* native libraries. I tried to get them to change the behavior, but it is setup this way for other reasons.

Looking closer at the item metadata available:

We don't even have %(RuntimeIdentifier), so I changed the message to be:

warning XA4301: Cannot determine ABI of native library 'C:\src\xamarin-android\packages\sqlitepclraw.lib.e_sqlite3.linux\1.1.11\runtimes\linux-arm64\native\libe_sqlite3.so'. Remove the 'SQLitePCLRaw.lib.e_sqlite3.linux' NuGet package, or notify the library author.

Let me know if you have other ideas, thanks.

…especially when I look at this: XA4301_ABI_RID won't be emitted if the lib is in a directory named after an ABI we know about, %(RuntimeIdentifier) be damned.

Presumably if %(RuntimeIdentifier) doesn't "match", it's unusable, e.g. trying to use a "desktop" Linux .so on Android is doomed, because libc.so is in the wrong location (among other things). Should we "fail early" and error, and check before calling MonoAndroidHelper.GetNativeLibraryAbi()? Or should we "fail at runtime" and warn -- as is done in this PR -- if the .so can't actually be used?

Which dovetails back with the warning message: if an unsupported %(RuntimeIdentifier) means "this has no chance of working", then the message needs to state that, and the fix is to remove the offending .so file. If it has a chance of working, then XA4301_ABI_RID should mirror XA4301_ABI, and mention that moving the .so into a directory with the ABI name will work.

As-is, the XA4301_ABI_RID warning means nothing.

I don't believe the %(RuntimeIdentifier) metadata would be present in user projects. It would only be present from NuGet packages.

Do you think the existing checks here needs to be changed?

https://github.com/xamarin/xamarin-android/blob/866085a611579ae270289751e46d7388c97f4251/src/Xamarin.Android.Build.Tasks/Utilities/MonoAndroidHelper.cs#L286-L313

I think it will already check %(RuntimeIdentifier) before directory names.