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Fixes: #1155
Context: https://docs.oracle.com/javase/tutorial/java/generics/bridgeMethods.html
A *bridge method* is a Java compiler-generated method "overload"
which deals with type coercion, to support Java type erasure:
package com.google.mlkit.vision.objects;
// https://developers.google.com/android/reference/com/google/mlkit/vision/objects/ObjectDetectorOptionsBase
public class ObjectDetectorOptionsBase {
/** @hide */ public static class Builder<B extends Builder> {
public B setDetectorMode(int detectorMode) {…}
}
}
package com.google.mlkit.vision.objects.defaults;
public class ObjectDetectorOptions {
// https://developers.google.com/android/reference/com/google/mlkit/vision/objects/defaults/ObjectDetectorOptions.Builder
public static class Builder extends ObjectDetectorOptionsBase.Builder<Builder> {
public Builder setDetectorMode(int detectorMode) {…}
}
}
It *looks like* there is only one
`ObjectDetectorOptions.Builder.setDetectorMode()` method, but there
are in fact *two*. The first is the bridge method (`ACC_BRIDGE`),
the second method is the "real" method; they differ on return type:
% javap -cp classes.jar -s -v 'com/google/mlkit/vision/objects/defaults/ObjectDetectorOptions$Builder'
…
public final com.google.mlkit.vision.objects.ObjectDetectorOptionsBase$Builder setDetectorMode(int);
descriptor: (I)Lcom/google/mlkit/vision/objects/ObjectDetectorOptionsBase$Builder;
flags: (0x1051) ACC_PUBLIC, ACC_FINAL, ACC_BRIDGE, ACC_SYNTHETIC
…
public com.google.mlkit.vision.objects.defaults.ObjectDetectorOptions$Builder setDetectorMode(int);
descriptor: (I)Lcom/google/mlkit/vision/objects/defaults/ObjectDetectorOptions$Builder;
flags: (0x0001) ACC_PUBLIC
This is represented within `class-parse` XML as:
<method abstract="false" deprecated="not deprecated" final="false" name="setDetectorMode" jni-signature="(I)Lcom/google/mlkit/vision/objects/defaults/ObjectDetectorOptions$Builder;" bridge="false" native="false" return="com.google.mlkit.vision.objects.defaults.ObjectDetectorOptions.Builder" jni-return="Lcom/google/mlkit/vision/objects/defaults/ObjectDetectorOptions$Builder;" static="false" synchronized="false" synthetic="false" visibility="public" return-not-null="true">
<parameter name="detectorMode" type="int" jni-type="I" />
</method>
<method abstract="false" deprecated="not deprecated" final="true" name="setDetectorMode" jni-signature="(I)Lcom/google/mlkit/vision/objects/ObjectDetectorOptionsBase$Builder;" bridge="true" native="false" return="java.lang.Object" jni-return="Lcom/google/mlkit/vision/objects/ObjectDetectorOptionsBase$Builder;" static="false" synchronized="false" synthetic="true" visibility="public" return-not-null="true">
<parameter name="p0" type="int" jni-type="I" />
</method>
The method with `bridge="true"` is the bridge method.
When bound in C#, this causes an issue because two methods cannot
have the same method name and parameter types:
// C# binding
public partial class ObjectDetectorOptions {
public partial class Builder {
public virtual MLKit.Vision.Objects.Defaults.ObjectDetectorOptions.Builder SetDetectorMode (int detectorMode);
public virtual MLKit.Vision.Objects.ObjectDetectorOptionsBase.Builder SetDetectorMode (int p0);
}
}
We can set `managedName` metadata to rename one of these methods:
<attr path="//method[@name='setDetectorMode' and @bridge='true']" name="managedName>SetDetectorMode2</attr>
However, we generate the callback delegate field with the algorithm
`$"cb_{JavaName}{IDSignature}"`, so this identifier is still used
twice, preventing C# compilation:
// C# binding
public partial class ObjectDetectorOptions {
public partial class Builder {
static Delegate cb_setDetectorMode_I;
static Delegate cb_setDetectorMode_I;
}
}
The solution is to add both the _managed_ name and the return type to
the callback naming algorithm to ensure that it will always be unique
for a method: `$"cb_{JavaName}_{Name}{IDSignatureWithReturnType}"`:
// C# binding
public partial class ObjectDetectorOptions {
public partial class Builder {
static Delegate cb_setDetectorMode_SetDetectorMode_I_Lcom_google_mlkit_vision_objects_defaults_ObjectDetectorOptions$Builder_;
static Delegate cb_setDetectorMode_SetDetectorMode2_I_Lcom_google_mlkit_vision_objects_ObjectDetectorOptions$Builder_;
}
}
Copy file name to clipboardExpand all lines: tests/generator-Tests/Unit-Tests/CodeGeneratorExpectedResults/Common/WriteInterfaceRedeclaredDefaultMethod.txt
Copy file name to clipboardExpand all lines: tests/generator-Tests/Unit-Tests/CodeGeneratorExpectedResults/XAJavaInterop1-NRT/WriteMethodWithCharSequenceArrays.txt
+4-4Lines changed: 4 additions & 4 deletions
Original file line number
Diff line number
Diff line change
@@ -29,13 +29,13 @@ public partial class MyClass : Java.Lang.Object {
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