[Java.Interop] Fix JNI signature generating #249
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Commit dotnet@cb161d2 introduced a regression described in dotnet/android#1149 (comment) The signature of the `InitializeCreator` method was wrongly calculated as `()Ljava/lang/Object;` instead of original `()Lmd59b7a7576784821ea63294fbca8600da1/Creator_1;` The reason for that is, that dotnet@cb161d2#diff-9e153905b02dbe50c0e0b874ba40bf3eR262 started using `IEnumerable<T>::OfType<T>`, which traverses inheritance, unlike the original `Type::GetCustomAttributes` called with `inherit = false`. Thus for the `Creator<Player>` we got the `RegisterAttribute` from the parent type `Java.Lang.Object` which led to non-null result from `ToJniNameFromAttributes` method. At the end the result was used here dotnet@cb161d2#diff-9e153905b02dbe50c0e0b874ba40bf3eR361 instead of returning `ToJniName (type, exportKind)` result.
jonpryor
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Jan 9, 2018
Fixes: dotnet/android#1149 Commit cb161d2 broke the use of `[Java.Interop.ExportAttribute]` and `[Java.Interop.ExportFieldAttribute]`. Repro: 1. [Create a class with an `[Export]` or `[ExportField]` method][0]: partial class MyParcelable : Java.Lang.Object, IParcelable { [ExportField ("CREATOR")] public static MyParcelableCreator InitializeCreator () { /* ... */ } } 2. Launch the app, and cause the `MyParcelable` Java Callable Wrapper (JCW) to be initialized: // Will eventually cause JCW MyParcelable.class to be init'd var whatever = new MyParcelable(); Expected result: It works! Actual result: System.InvalidOperationException: Specified managed method 'InitializeCreator' was not found. Signature: ()Lmd5<<whatever>>/MyParcelableCreator; at Android.Runtime.JNIEnv.RegisterJniNatives (System.IntPtr typeName_ptr, System.Int32 typeName_len, System.IntPtr jniClass, System.IntPtr methods_ptr, System.Int32 methods_len) [0x001d2] in <36a2bb1be1a64b51b22cbef15eee5437>:0 at (wrapper managed-to-native) Java.Interop.NativeMethods.java_interop_jnienv_alloc_object(intptr,intptr&,intptr) at Java.Interop.JniEnvironment+Object.AllocObject (Java.Interop.JniObjectReference type) [0x00027] in <8e80eb3ca41f4c3eb745bd7c73458796>:0 at Java.Interop.JniType.AllocObject () [0x0000c] in <8e80eb3ca41f4c3eb745bd7c73458796>:0 at Java.Interop.JniPeerMembers+JniInstanceMethods.StartCreateInstance (System.String constructorSignature, System.Type declaringType, Java.Interop.JniArgumentValue* parameters) [0x0003e] in <8e80eb3ca41f4c3eb745bd7c73458796>:0 at Java.Lang.Object..ctor () [0x00034] in <36a2bb1be1a64b51b22cbef15eee5437>:0 ... [0]: https://github.com/xamarin/monodroid-samples/blob/f944f42001fa134915069fa7bbb9cb493bfd446d/ExportAttribute/ExportAttributeTest/MainActivity.cs#L52-L86 The `InvalidOperationException` is thrown from [`JNIEnv.RegisterJniNatives()` for `__export__` methods][reg], which requires that `JavaNativeTypeManager.GetJniSignature(MethodInfo)` return the same value as what the Java Callable Wrapper contains. [reg]: https://github.com/xamarin/xamarin-android/blob/master/src/Mono.Android/Android.Runtime/JNIEnv.cs#L172-L178 Rephrased: we require that the Reflection-based `JavaNativeTypeManager.GetJniSignature(MethodInfo)` generate identical values as the Cecil-based `JavaNativeTypeManager.GetJniSignature(MethodDefinition)`: the former used by `JNIEnv.RegisterJniNatives()`, the latter by `JavaCallableWrapperGenerator`. These *must* be consistent. The problem is, they weren't: `JavaNativeTypeManager.ToJniNameFromAttributes(Type)` -- called by `JavaNativeTypeManager.GetJniSignature(MethodInfo)` and others -- was erroneously updated to check for custom attributes on the specified `Type` *and all base classes*. Checking base classes would eventually cause `Java.Lang.Object` to be checked, causing *everything* to become `java.lang.Object` unless explicitly overridden in the inheritance chain (e.g. `Activity`, which has its own `[Register]` attribute). The result is that `JavaNativeTypeManager.GetJniSignature(MethodInfo)` for `MyParcelable.InitializeCreator()` was returning: ()Ljava/lang/Object; while `JavaNativeTypeManager.GetJniSignature(MethodDefinition)` was generating: ()Lmd5<<whatever>>/MyParcelableCreator; Because these didn't match, `InvalidOperationException` was thrown. Fix `JavaNativeTypeManager.ToJniNameFromAttributes(Type)` so that base classes are *not* searched for custom attributes, restoring prior behavior.
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Commit
cb161d2
introduced a regression described in
dotnet/android#1149 (comment)
The signature of the
InitializeCreatormethod was wrongly calculatedas
()Ljava/lang/Object;instead of original()Lmd59b7a7576784821ea63294fbca8600da1/Creator_1;The reason for that is, that
cb161d2#diff-9e153905b02dbe50c0e0b874ba40bf3eR262
started using
IEnumerable<T>::OfType<T>, which traversesinheritance, unlike the original
Type::GetCustomAttributescalledwith
inherit = false.Thus for the
Creator<Player>we got theRegisterAttributefrom theparent type
Java.Lang.Objectwhich led to non-null result fromToJniNameFromAttributesmethod. At the end the result was used herecb161d2#diff-9e153905b02dbe50c0e0b874ba40bf3eR361
instead of returning
ToJniName (type, exportKind)result.