Overriding constructors for classes inheriting from Java

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#367 5 comments 0 reactions 1 assignee View on GitHub

@timfel is already working on this.

Since Jan 20, 2025.

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Description

As of the latest version (23.1.0), GraalPy does not support overriding constructors for Python classes that inherit from Java.

The example below throws an error when we try to create a custom Exception wrapper in Python:

package my.pack;

import org.graalvm.polyglot.Value;
import org.graalvm.polyglot.Context;

public class Main {

    static Context context = Context.newBuilder().allowAllAccess(true).build();
    static Value clz;

    public static void main(String[] args) {
        context.eval("python", """
            import java
            class ParseException(java.lang.Exception):
                def __init__(self, message):
                    self.__super__(message)
            """);

        clz = context.getBindings("python").getMember("ParseException");
        Value obj = clz.newInstance("Hello from Java");
    }
}
Result
// error
Exception in thread "main" TypeError: ParseException.__init__() missing 1 required positional argument: 'message'
        at org.graalvm.sdk/org.graalvm.polyglot.Value.newInstance(Value.java:933)
        at my.pack.Main.main(Main.java:18)
Dominant language
Python
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