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[J.I, generator] Fix GetPeerMembers for interfaces. - #486
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jpobst
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Aug 28, 2019
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Updated to address review feedback. |
jonpryor pushed a commit
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Aug 29, 2019
Context: dotnet/android#3533 Consider the following Java interface which contains a default interface method: // Java package com.xamarin.android; public interface DefaultMethodsInterface { default int foo () { return 0; } } This is bound as: // C# Binding public partial interface IDefaultMethodsInterface : IJavaPeerable { static readonly JniPeerMembers _members = new JniPeerMembers ( "java/DefaultMethodsInterface", typeof (IDefaultMethodsInterface)); [Register ("foo", "()V", "…")] virtual unsafe int Foo () { return _members.InstanceMethods.InvokeVirtualInt32Method ("foo.()V", this, null); } } If we "implement" the interface from C# *without* implementing `IDefaultMethodsInterface.Foo()`: // C# class ManagedOverrideDefault : Java.Lang.Object, IDefaultMethodsInterface { } Then invoke the default interface method: var over = new ManagedOverrideDefault (); (over as IDefaultMethodsInterface).Foo (); The attempt to invoke the default implementation of `IDefaultMethodsInterface.Foo()` causes a crash: Java.Lang.NoSuchMethodError : no non-static method "Ljava/lang/Object;.foo()I" The cause of the crash is as follows: `IDefaultMethodsInterface.Foo()` calls `JniPeerMembers.JniInstanceMethods.InvokeVirtualInt32Method()` tries to determine if the method is overridden, and if the method is *not* overridden -- as is the case here -- then we hit the non-virtual invocation path: // src/Java.Interop/Java.Interop/JniPeerMembers.JniInstanceMethods_Invoke.cs var j = Members.GetPeerMembers (self); var n = j.InstanceMethods.GetMethodInfo (encodedMember); return JniEnvironment.InstanceMethods.CallNonvirtualIntMethod (self.PeerReference, j.JniPeerType.PeerReference, n, parameters); `JniInstanceMethods.Members` will be the `IDefaultMethodsInterface._members` field, and `Members.GetPeerMembers()` would return `self.JniPeerMembers`. Because this is a C# class which inherits `Java.Lang.Object`, `Java.Lang.Object._members` is returned. We then attempt to resolve `foo()` from `java.lang.Object`, which *does not exist*, which is why the `NoSuchMethodError` is thrown. The fix is to "intercept" the `Members.GetPeerMembers()` invocation so that `j` refers to `IDefaultMethodsInterface._members`, *not* `Java.Lang.Object._members`. This would allow `n` to refer to `DefaultMethodsInterface.foo()`, which *does* exist, and *can* be invoked via `JniEnvironment.InstanceMethods.CallNonvirtualIntMethod()`. Add the following `JniPeerMembers` constructor overload: partial class JniPeerMembers { public JniPeerMembers (string jniPeerTypeName, Type managedPeerType, bool isInterface); } Update `JniPeerMembers.GetPeerMembers()` so that if `isInterface` is true, we return `this` (the *interface*s `JniPeerMembers` instance). Update `generator` so that `_members` construction within interfaces sets the `isInterface` parameter to true, resulting in: partial interface IDefaultMethodsInterface { static readonly JniPeerMembers _members = new JniPeerMembers ( "java/DefaultMethodsInterface", typeof (IDefaultMethodsInterface), isInterface: true); } This allows `(over as IDefaultMethodsInterface).Foo()` to work without an exception being thrown.
steveisok pushed a commit
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Aug 30, 2019
Context: dotnet/android#3533 Consider the following Java interface which contains a default interface method: // Java package com.xamarin.android; public interface DefaultMethodsInterface { default int foo () { return 0; } } This is bound as: // C# Binding public partial interface IDefaultMethodsInterface : IJavaPeerable { static readonly JniPeerMembers _members = new JniPeerMembers ( "java/DefaultMethodsInterface", typeof (IDefaultMethodsInterface)); [Register ("foo", "()V", "…")] virtual unsafe int Foo () { return _members.InstanceMethods.InvokeVirtualInt32Method ("foo.()V", this, null); } } If we "implement" the interface from C# *without* implementing `IDefaultMethodsInterface.Foo()`: // C# class ManagedOverrideDefault : Java.Lang.Object, IDefaultMethodsInterface { } Then invoke the default interface method: var over = new ManagedOverrideDefault (); (over as IDefaultMethodsInterface).Foo (); The attempt to invoke the default implementation of `IDefaultMethodsInterface.Foo()` causes a crash: Java.Lang.NoSuchMethodError : no non-static method "Ljava/lang/Object;.foo()I" The cause of the crash is as follows: `IDefaultMethodsInterface.Foo()` calls `JniPeerMembers.JniInstanceMethods.InvokeVirtualInt32Method()` tries to determine if the method is overridden, and if the method is *not* overridden -- as is the case here -- then we hit the non-virtual invocation path: // src/Java.Interop/Java.Interop/JniPeerMembers.JniInstanceMethods_Invoke.cs var j = Members.GetPeerMembers (self); var n = j.InstanceMethods.GetMethodInfo (encodedMember); return JniEnvironment.InstanceMethods.CallNonvirtualIntMethod (self.PeerReference, j.JniPeerType.PeerReference, n, parameters); `JniInstanceMethods.Members` will be the `IDefaultMethodsInterface._members` field, and `Members.GetPeerMembers()` would return `self.JniPeerMembers`. Because this is a C# class which inherits `Java.Lang.Object`, `Java.Lang.Object._members` is returned. We then attempt to resolve `foo()` from `java.lang.Object`, which *does not exist*, which is why the `NoSuchMethodError` is thrown. The fix is to "intercept" the `Members.GetPeerMembers()` invocation so that `j` refers to `IDefaultMethodsInterface._members`, *not* `Java.Lang.Object._members`. This would allow `n` to refer to `DefaultMethodsInterface.foo()`, which *does* exist, and *can* be invoked via `JniEnvironment.InstanceMethods.CallNonvirtualIntMethod()`. Add the following `JniPeerMembers` constructor overload: partial class JniPeerMembers { public JniPeerMembers (string jniPeerTypeName, Type managedPeerType, bool isInterface); } Update `JniPeerMembers.GetPeerMembers()` so that if `isInterface` is true, we return `this` (the *interface*s `JniPeerMembers` instance). Update `generator` so that `_members` construction within interfaces sets the `isInterface` parameter to true, resulting in: partial interface IDefaultMethodsInterface { static readonly JniPeerMembers _members = new JniPeerMembers ( "java/DefaultMethodsInterface", typeof (IDefaultMethodsInterface), isInterface: true); } This allows `(over as IDefaultMethodsInterface).Foo()` to work without an exception being thrown.
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The following DIM case currently fails:
with:
This adds a parameter to the
JniPeerMembersconstructor denoting this type is an Interface rather than a Class, so thatGetPeerMemberscan correctly resolve the method.