Calling toString on an Enso object implementing a Java interface causes Panic

[radeusgd]

Sometimes when passing Enso objects to Java, we can make them implement some interface by ensuring that the Enso object has all methods of that interface. This makes it easier to interact with Enso objects on the Java side (once can just use the interface instead of Polyglot methods).

It seems that toString which is expected from all Java objects is not picked up properly.

I'm not exactly sure if this is a bug in Enso or Graal itself.

Repro

Let's create a file Foo.java:

package foo;

public class Foo {
    public static interface Fooable {
        public long foo();
    }

    public static long callFoo(Fooable f) {
        long x = f.foo();
        System.out.println("Foo.foo() returned " + x);
        return x;
    }

    public static void showObject(Object o) {
        System.out.println("Object = " + o.toString());
    }

    public static long callFooAndShow(Fooable f) {
        long x = f.foo();
        System.out.println("{" + f.toString() + "}.foo() returned " + x);
        return x;
    }
}

and then put it in a polyglot project, with src/Main.enso being:

from Standard.Base import all

polyglot java import foo.Foo

type My_Fooable_Implementation
    Instance x

    foo : Integer
    foo self = 100+self.x

main =
   fooable = My_Fooable_Implementation.Instance 23
   IO.println fooable.foo
   IO.println fooable.to_text
   IO.println (Foo.callFoo fooable)
   IO.println (Foo.showObject fooable)
   IO.println (Foo.callFooAndShow fooable)

Actual behaviour

The project as described above, when run yields:

123
(Instance 23)
Foo.foo() returned 123
123
Object = (Instance 23)
Nothing
Execution finished with an error: Method `toString` of type My_Fooable_Implementation could not be found.
        at <java> org.graalvm.truffle/com.oracle.truffle.polyglot.PolyglotObjectProxyHandler.invoke(PolyglotObjectProxyHandler.java:105)
        at <java> jdk.proxy5/jdk.proxy5.$Proxy44.toString(Unknown Source)
        at <java> foo.Foo.callFooAndShow(Foo.java:20)
        at <enso> Main.main<arg-1>(src\Main.enso:17:16-41)
        at <enso> Main.main(src\Main.enso:17:4-42)

Expected behaviour

The program should execute without errors and yield:

123
(Instance 23)
Foo.foo() returned 123
123
Object = (Instance 23)
Nothing
{(Instance 23)}.foo() returned 123
123

The toString call on the Proxy object should delegate to the to_text method of the Enso object. As we can see, if we pass it as an Object that correctly happens. But if we pass it as this 'interface proxy' - that fails.

[JaroslavTulach]

Exposing java.lang.Object methods to guest languages is considered as security problem. I fixed that by designing HostAccess. Enso is using HostAccess.PUBLIC, but even that doesn't allow access to methods like getClass(), hashCode() and toString().

I understand that logging is problematic when toString() doesn't return anything at all. But I am not sure whether there is something to do about it.

[JaroslavTulach]

Here is a small program that demonstrates the behavior on Python object:

import org.graalvm.polyglot.Context;
import org.graalvm.polyglot.HostAccess;

public class ToString {
    public interface WithX {
        int x();
    }

    public static void main(String[] args) {
        try (
            var ctx = Context.newBuilder()
                .allowHostAccess(HostAccess.ALL)
                .build()
        ) {
            var obj = ctx.eval("python", """
            class WithX:
                def __init__(self, v):
                    self.x = v

            WithX(42)
            """).as(WithX.class);

            System.out.println("obj.x: " + obj.x());
            var txt = obj.toString();
            System.out.println("obj  : " + txt);
        }
    }
}

when executed as graalvm-17/bin/java ToString.java it works and it prints:

obj.x: 42
obj  : <__main__.WithX object at 0x254cc548>

Something else must be wrong in the Enso case...

[JaroslavTulach]

Probably related to PolyglotObjectProxyHandler that caches UnsupportedOperationException and then handles Object.toString in a special way. But we throw different exception:

    @Override
    public Object invoke(Object proxy, Method method, Object[] arguments) throws Throwable {
        CompilerAsserts.neverPartOfCompilation();
        Object[] resolvedArguments = arguments == null ? EMPTY : arguments;
        try {
            return invoke.call(languageContext, obj, method, resolvedArguments);
        } catch (UnsupportedOperationException e) {
            try {
                return PolyglotFunctionProxyHandler.invokeDefault(this, proxy, method, resolvedArguments);
            } catch (Exception innerE) {
                e.addSuppressed(innerE);
                throw e;
            }
        }
    }

[radeusgd]

when executed as graalvm-17/bin/java ToString.java it works and it prints:

so that sounds like we should be able to fix this issue in Enso, because it's not a Graal issue, right? :) That sounds nice

[enso-bot]

Jaroslav Tulach reports a new STANDUP for yesterday (2023-08-02):

Progress: - Investigating toString(): #7437 (comment)

• Got approvals for BigInteger: Adopting GraalVM's support for BigInteger #7420 (comment)
• review round builtin: Implement Number.round as a builtin #7460 (review)
• review equals/hash: Respect database backend naming limitations when generating table/column names and validate user-provided names to avoid silent name clashes; process JDBC warnings reported from backends #7428 (review)
• standups & meetings It should be finished by 2023-08-04.

Next Day: Benchmarking BigInteger and working on toString()

[enso-bot]

Jaroslav Tulach reports a new STANDUP for yesterday (2023-08-03):

Progress: - toString PR: #7487

• BigInteger PR integrated: Adopting GraalVM's support for BigInteger #7420
• JMH diff: https://github.com/enso-org/enso/pull/7101/files#r1283141063
• Pair debugging with GregT: https://github.com/enso-org/enso/pull/7460/files#r1283283587
• Trying to understand why EnsoContext.get isn't compilation constant
• discussion with GraalVM guys: https://graalvm.slack.com/archives/CNQSB2DHD/p1691076832287559
• PR with benchmarks: Exclusive context policy ensures EnsoContext.get returns compilation constant #7493 It should be finished by 2023-08-04.

Next Day: Finish toString() & other bugfixing

GitHub

Invoke all Enso benchmarks via JMH by Akirathan · Pull Request #7101 · enso-org/enso

Closes #7323 Pull Request Description Motivation There are a lot of Enso-only benchmarks in test/Benchmarks project. These benchmarks are not run on the CI (they are, but only in dry-run). We want ...

GitHub

Implement Number.round as a builtin by GregoryTravis · Pull Request #7460 · enso-org/enso

Checklist Please ensure that the following checklist has been satisfied before submitting the PR:

The documentation has been updated, if necessary.
Screenshots/screencasts have been attached, if...

Slack

[enso-bot]

Jaroslav Tulach reports a new STANDUP for yesterday (2023-08-04):

Progress: - Investigating toString exception: 1c3f396

• Test for EnsoContext: Exclusive context policy ensures EnsoContext.get returns compilation constant #7493 (comment)
• bug of EnsoContext for GraalVM guys: Cached.isAdoptable() = false prevents compile time constant access to ContextReference oracle/graal#7131
• workarounding EnsoContext: 9659ca0
• meeting Pawel B. - Sentry logging, reusing program-manager (but S3 and DB)
• standups It should be finished by 2023-08-04.

Next Day: Finish toString()

[enso-bot]

Jaroslav Tulach reports a new 🔴 DELAY for yesterday (2023-08-06):

Summary: There is 7 days delay in implementation of the Calling toString on an Enso object implementing a Java interface causes Panic (#7437) task.
It will cause 7 days delay for the delivery of this weekly plan.

Got additional requests to fix

Delay Cause: Additional fixes were needed. More than originally estimated.

Possible solutions: Working over weekend fixed all the issues (review pending).

[enso-bot]

Jaroslav Tulach reports a new 🔴 DELAY for yesterday (2023-08-06):

Summary: There is 7 days delay in implementation of the Calling toString on an Enso object implementing a Java interface causes Panic (#7437) task.
It will cause 7 days delay for the delivery of this weekly plan.

Got additional requests to fix

Delay Cause: Additional fixes were needed. More than originally estimated.

Possible solutions: Working over weekend fixed all the issues (review pending).

[enso-bot]

Jaroslav Tulach reports a new STANDUP for yesterday (2023-08-06):

Progress: - toString() is (almost) green: #7487 (comment)

• GraalVM prepares big changes: https://graalvm.slack.com/archives/CNBFR78F9/p1691320449364759?thread_ts=1691241119.810719&cid=CNBFR78F9
• building Enso on my Mac
• reporting test failure: Unit tests fail on Mac OSX (x64) #7505 It should be finished by 2023-08-18.

Next Day: EnsoContext & other bugfixes

[enso-bot]

Jaroslav Tulach reports a new STANDUP for yesterday (2023-08-07):

Progress: - demo & other meetings It should be finished by 2023-08-18.

Next Day: EnsoContext & other bugfixes