The DefaultStackTraceElementObject.getExecutableName breaks the contract of InteropLibrary

[radeusgd]

I've been encountering this issue running the OpenJDK Runtime Environment GraalVM CE 17.0.7+7.1 (build 17.0.7+7-jvmci-23.0-b12) version, but I can confirm that it is still present in the latest sources on the master branch.

graal/truffle/src/com.oracle.truffle.api.interop/src/com/oracle/truffle/api/interop/InteropLibrary.java

Lines 274 to 297 in f2bd761

	/**
	* Returns {@code true} if the receiver has an executable name. Invoking this message does not
	* cause any observable side-effects. Returns {@code false} by default.
	*
	* @see #getExecutableName(Object)
	* @since 20.3
	*/
	@Abstract(ifExported = {"getExecutableName"})
	public boolean hasExecutableName(Object receiver) {
	return false;
	}
	/**
	* Returns executable name of the receiver. Throws {@code UnsupportedMessageException} when the
	* receiver is has no {@link #hasExecutableName(Object) executable name}. The return value is an
	* interop value that is guaranteed to return <code>true</code> for {@link #isString(Object)}.
	*
	* @see #hasExecutableName(Object)
	* @since 20.3
	*/
	@Abstract(ifExported = {"hasExecutableName"})
	public Object getExecutableName(Object receiver) throws UnsupportedMessageException {
	throw UnsupportedMessageException.create();
	}

The contract of InteropLibrary says that if the receiver has no executable name (i.e. hasExecutableName(receiver) == false), then getExecutableName throws UnsupportedMessageException. It also says that otherwise, "The return value is an interop value that is guaranteed to return true for isString".

However, the code for DefaultStackTraceElementObject violates this contract:

graal/truffle/src/com.oracle.truffle.api.exception/src/com/oracle/truffle/api/exception/DefaultStackTraceElementObject.java

Lines 53 to 74 in f2bd761

	final class DefaultStackTraceElementObject implements TruffleObject {
	private final RootNode rootNode;
	private final SourceSection sourceSection;
	DefaultStackTraceElementObject(RootNode rootNode, SourceSection sourceSection) {
	this.rootNode = rootNode;
	this.sourceSection = sourceSection;
	}
	@ExportMessage
	@TruffleBoundary
	@SuppressWarnings("static-method")
	boolean hasExecutableName() {
	return rootNode.getName() != null;
	}
	@ExportMessage
	@TruffleBoundary
	Object getExecutableName() {
	return rootNode.getName();
	}

When the rootNode.getName() == null, it does report hasExecutableName to be false, but asking for it, instead of throwing UnsupportedMessageException as required by contract, it returns null - which is not an interop value that "is guaranteed to return true for isString".

Thus code relying on the contract of InteropLibrary, assuming that getExecutableName either returns a valid text value or throws an exception, breaks when it encounters a DefaultStackTraceElementObject whose rootNode.getName() == null.