[generator] Don't generate unexpected NRT types like void? (#856)

Context: #850 (comment)
When a user binds a Java library that contains a Java interface which
implements another Java interface:
// Java; android.jar
public interface /* android.view. */ Menu {…}
// Java; androidx.core.core.jar
public interface /* androidx.core.internal.view. */ SupportMenu implements android.view.Menu {…}
then when we create the binding for the "leaf" interface:
// C# binding for androidx.core.core
namespace AndroidX.Core.Internal.View {
public interface ISupportMenu : Android.Views.IMenu {…}
internal partial class ISupportMenuInvoker : Java.Lang.Object, ISupportMenu {
// …
}
}
The generated `*Invoker` type implements all methods for all
implemented interfaces, e.g. methods from both `IMenu` and
`ISupportMenu`.
When:
1. The base interface (e.g. `IMenu`) comes from a referenced
assembly, *and*
2. `$(Nullable)`=Enable when binding the derived interface
then we interpret the return types on imported interface methods as
*always* being of a nullable type, even for types such as `void`:
// C# binding for androidx.core.core with $(Nullable)=Enable
partial class ISupportMenuInvoker : Java.Lang.Object, ISupportMenu {
public unsafe void? Clear () {…}
}
This results in errors from the C# compiler:
Error CS1519: Invalid token '?' in class, record, struct, or interface member declaration
Error CS1520: Method must have a return type
Error CS0535: 'ISupportMenuInvoker' does not implement interface member 'IMenu.Clear()'
The culprit is twofold:
- In `CecilApiImporter`, we set `Method.ManagedReturn` to
`System.Void` instead of `void`.
- In `CodeGenerationOptions`, we only check for `void` to omit the
null operator, not `System.Void`.
Note this also happens for all primitive types like
`System.Int32`/`int`.
This commit fixes both aspects:
- Change `Method.ManagedReturn` to contain primitive types instead
of fully qualified types.
- Update `CodeGenerationOptions.GetNullable()` to correctly handle
fully qualified types if one slips through.
With this change, all of AndroidX/GooglePlayServices/FaceBook/MLKit
can be successfully compiled with `<Nullable>enable</Nullable>`.

Author: jpobst

tests/generator-Tests/Unit-Tests/CodeGenerationOptionsTests.cs

@@ -51,5 +51,21 @@ public void GetOutputNameUseGlobal ()
 Assert.AreEqual("global::System.Collections.Generic.List<global::System.Collections.Generic.List<string>.Enumerator[]>",
 opt.GetOutputName("System.Collections.Generic.List<System.Collections.Generic.List<string>.Enumerator[]>"));
 }
+
+[Test]
+publicvoidGetTypeReferenceName_Nullable()
+{
+varopt=newCodeGenerationOptions{SupportNullableReferenceTypes=true};
+
+varsystem_void=newReturnValue(null,"void","System.Void",false,false);
+system_void.Validate(opt,null,null);
+
+Assert.AreEqual("void",opt.GetTypeReferenceName(system_void));
+
+varprimitive_void=newReturnValue(null,"void","void",false,false);
+primitive_void.Validate(opt,null,null);
+
+Assert.AreEqual("void",opt.GetTypeReferenceName(primitive_void));
+}
 }
 }

tests/generator-Tests/Unit-Tests/ManagedTests.cs

@@ -121,7 +121,7 @@ public void Method ()
 
 Assert.AreEqual("public",method.Visibility);
 Assert.AreEqual("void",method.Return);
-Assert.AreEqual("System.Void",method.ReturnType);
+Assert.AreEqual("void",method.ReturnType);
 Assert.AreEqual("Bar",method.Name);
 Assert.AreEqual("bar",method.JavaName);
 Assert.AreEqual("()V",method.JniSignature);
@@ -165,7 +165,7 @@ public void MethodWithParameters ()
 Assert.IsTrue(method.Validate(newCodeGenerationOptions(),newGenericParameterDefinitionList(),newCodeGeneratorContext()),"method.Validate failed!");
 Assert.AreEqual("(ZID)Ljava/lang/String;",method.JniSignature);
 Assert.AreEqual("java.lang.String",method.Return);
-Assert.AreEqual("System.String",method.ManagedReturn);
+Assert.AreEqual("string",method.ManagedReturn);
 
 varparameter=method.Parameters[0];
 Assert.AreEqual("a",parameter.Name);

tools/generator/CodeGenerationOptions.cs

@@ -141,21 +141,23 @@ string GetNullable (string s)
 switch(s){
 case"void":
 case"int":
-//case "int[]":
 case"bool":
-//case "bool[]":
 case"float":
-//case "float[]":
 case"sbyte":
-//case "sbyte[]":
 case"long":
-//case "long[]":
 case"char":
-//case "char[]":
 case"double":
-//case "double[]":
 case"short":
-//case "short[]":
+case"System.Boolean":
+case"System.Byte":
+case"System.Char":
+case"System.Double":
+case"System.Int16":
+case"System.Int32":
+case"System.Int64":
+case"System.Single":
+case"System.SByte":
+case"System.Void":
 case"Android.Graphics.Color":
 returnstring.Empty;
 }

tools/generator/Extensions/ManagedExtensions.cs

@@ -65,6 +65,25 @@ public static string StripArity (this string type)
 
 returntype;
 }
+
+// Convert a fully qualified type like "System.Void" to the primitive type "void" if applicable
+publicstaticstringFilterPrimitive(thisstringtype)
+{
+returntypeswitch{
+"System.Boolean"=>"bool",
+"System.Char"=>"char",
+"System.Byte"=>"byte",
+"System.SByte"=>"byte",
+"System.Int16"=>"short",
+"System.Int32"=>"int",
+"System.Int64"=>"long",
+"System.Single"=>"float",
+"System.Double"=>"double",
+"System.Void"=>"void",
+"System.String"=>"string",
+ _ =>type
+};
+}
 }
 #endif
 }

tools/generator/Java.Interop.Tools.Generator.Importers/CecilApiImporter.cs

@@ -196,8 +196,8 @@ public static Method CreateMethod (GenBase declaringType, MethodDefinition m)
 IsStatic=m.IsStatic,
 IsVirtual=m.IsVirtual,
 JavaName=reg_attr!=null?((string)reg_attr.ConstructorArguments[0].Value):m.Name,
-ManagedReturn=m.ReturnType.FullNameCorrected().StripArity(),
-Return=m.ReturnType.FullNameCorrected().StripArity(),
+ManagedReturn=m.ReturnType.FullNameCorrected().StripArity().FilterPrimitive(),
+Return=m.ReturnType.FullNameCorrected().StripArity().FilterPrimitive(),
 Visibility=m.Visibility()
 };