Can't call Java desugared static interface methods in android libraries before API-24

[Dolfik1]

Steps to Reproduce

1. Generate bindings to any library with static interface method
2. Set Minimum Android version to API Level 23 or lower
3. Call static interface method

WebRtcTest.zip

Expected Behavior

Method called successfully

Actual Behavior

Java.Lang.NoSuchMethodError: 'no static method "Lorg/webrtc/EglBase;.create()Lorg/webrtc/EglBase;"'

Other

There are fix for Gradle: react-native-webrtc/react-native-webrtc#720 (comment)

Version Information

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Version 16.5.2
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[jonpryor]

The problem is caused by "desugaring", which "moves things around." In particular, if you run dexdump classes.dex on the classes.dex contained within the .apk, the only create method with a "type" of ()Lorg/webrtc/EglBase; is declared in Lorg/webrtc/EglBase$-CC;:

$ $HOME/android-toolchain/sdk/build-tools/29.0.2/dexdump classes.dex
…
Class #1481            -
  Class descriptor  : 'Lorg/webrtc/EglBase$-CC;'
  Access flags      : 0x1011 (PUBLIC FINAL SYNTHETIC)
  Superclass        : 'Ljava/lang/Object;'
  Interfaces        -
  Static fields     -
  Instance fields   -
  Direct methods    -
    …
    #1              : (in Lorg/webrtc/EglBase$-CC;)
      name          : 'create'
      type          : '()Lorg/webrtc/EglBase;'
      access        : 0x0009 (PUBLIC STATIC)
      code          -
      registers     : 2
      ins           : 0
      outs          : 2
      insns size    : 8 16-bit code units
      catches       : (none)
      positions     : 
        0x0000 line=170
      locals        : 

EglBase$-CC is not a class present within the original classes.jar. Equally important, our code is looking for the create method on org/webrtc/EglBase, not org/webrtc/EglBase$-CC;, and while org/webrtc/EglBase exists in classes.dex, it does not contain the static create method.

This is why the Java.Lang.NoSuchMethodError is thrown.

Disabling desugar allow the app to run, but requires -- as you note in step (2) -- that the Minimum Android version to API Level be 24 or higher. 26 in this case, actually, to avoid a different build error:

D8 : error : Invoke-customs are only supported starting with Android O (--min-api 26)

---

I'm not entirely sure how to address this on our end. We could skip binding static interface methods/etc. unless building against Mono.Android.dll v7.0, which would avoid the NoSuchMethodException… by removing the method entirely. (This isn't a "fix.") I'm also not sure it would actually work, because all Mono.Android.dlls have an assembly version of 0.0.0.0, so we'd have to "somehow" ensure that the v7.0 bit makes it into the NuGet package? (I don't understand how that process works.)

The only other fix I can think of is to IL-rewrite the binding assembly to replace appropriate instances of Lorg/webrtc/EglBase; with Lorg/webrtc/EglBase$-CC;, which could be done but could be "brittle".

[Dolfik1]

@jonpryor is it possible fix that via transforms without IL rewriting?

I tried to use this code, but it doesn't worked for me:

<add-node path="/api/package[@name='org.webrtc']">
  <interface abstract="true" deprecated="not deprecated" final="false" name="EglBaseCustom" static="false" visibility="public" jni-signature="Lorg/webrtc/EglBase;">
    <method abstract="false" deprecated="not deprecated" final="false" name="create" jni-signature="()Lorg/webrtc/EglBase$-CC;" 
		  bridge="false" native="false" return="org.webrtc.EglBase" jni-return="Lorg/webrtc/EglBase;" static="true" synchronized="false" synthetic="false" visibility="public">
    </method>
  </interface>
</add-node>```

[Dolfik1]

I found workaround for this issue:

namespace Org.Webrtc
{
	[Register("org/webrtc/EglBase$-CC", DoNotGenerateAcw = true)]
	public abstract class EglBaseStatic : Java.Lang.Object
	{
		internal EglBaseStatic()
		{
		}

		// Metadata.xml XPath method reference: path="/api/package[@name='org.webrtc']/interface[@name='EglBase']/method[@name='create' and count(parameter)=0]"
		[Register("create", "()Lorg/webrtc/EglBase;", "")]
		public static unsafe global::Org.Webrtc.IEglBase Create()
		{
			const string __id = "create.()Lorg/webrtc/EglBase;";
			try
			{
				var __rm = _members.StaticMethods.InvokeObjectMethod(__id, null);
				return global::Java.Lang.Object.GetObject<global::Org.Webrtc.IEglBase>(__rm.Handle, JniHandleOwnership.TransferLocalRef);
			}
			finally
			{
			}
		}

		static readonly JniPeerMembers _members = new XAPeerMembers("org/webrtc/EglBase$-CC", typeof(EglBaseStatic));
	}
}

But this workaround works only in Debug configuration. I got this exception in Release configuration:

Java.Lang.IncompatibleClassChangeError: no static method "Lorg/webrtc/EglBase$-CC;.create()Lorg/webrtc/EglBase;"
      at Java.Interop.JniEnvironment+StaticMethods.GetStaticMethodID (Java.Interop.JniObjectReference type, System.String name, System.String signature) [0x0005b] in <3f76ba23ba894c92a0082c32427fb8a5>:0 
      at Java.Interop.JniType.GetStaticMethod (System.String name, System.String signature) [0x0000c] in <3f76ba23ba894c92a0082c32427fb8a5>:0 
      at Java.Interop.JniPeerMembers+JniStaticMethods.GetMethodInfo (System.String encodedMember) [0x00036] in <3f76ba23ba894c92a0082c32427fb8a5>:0 
      at Java.Interop.JniPeerMembers+JniStaticMethods.InvokeObjectMethod (System.String encodedMember, Java.Interop.JniArgumentValue* parameters) [0x00000] in <3f76ba23ba894c92a0082c32427fb8a5>:0 
      at Org.Webrtc.EglBaseStatic.Create () [0x0000a] in <e9145eeab3c54ba095bbc83c7d9b5f7a>:0 

@jonpryor what do you think about this?