It is impossible to catch Panics in the GUI

[radeusgd]

I would like to be able to catch a panic for example in order to inspect its stack trace.

Ideally, the visualization should allow to show a stack trace for a panic by default, but that's probably another thing.

Expected behaviour

The same operations in the REPL work and allow to catch a Panic:

Uncaught panic

> r = Panic.throw "foo"
null:: warning: Unused variable r.
Evaluation failed with: foo
java.lang.Exception: foo
        at <enso>.Panic.throw(Unknown Source)
        at <enso>.<eval>(Unknown Source)
        at <enso>.Debug.breakpoint(Unknown Source)
        at <enso>.Rrepl::Rrepl::main(Rrepl.enso:46)
        at <unknown>.org.graalvm.polyglot.Value<Function>.execute(Unknown Source)

> r
null:: error: The name `r` could not be found.
Evaluation failed with: Compilation aborted due to errors.
java.lang.Exception: Compilation aborted due to errors.
        at <enso>.Debug.breakpoint(Unknown Source)
        at <enso>.Rrepl::Rrepl::main(Rrepl.enso:46)
        at <unknown>.org.graalvm.polyglot.Value<Function>.execute(Unknown Source)

Panic recovered as dataflow error

> r = Panic.recover Any (Panic.throw "foo")
null:: warning: Unused variable r.
>>> Nothing
> r
>>> (Error: 'foo')
> r.catch
>>> foo

Caught panic

> r = Panic.catch Any (Panic.throw "foo") c->c.payload
null:: warning: Unused variable r.
>>> Nothing
> r
>>> foo

[radeusgd]

Added a triage label because while the issue is showing up in the GUI, it likely may be an issue in the runtime.

[4e6]

I encountered this issue today. In the expression

Panic.catch Any (Panic.throw 42) _.payload

• when the Panic.throw 42 sub-expression is instrumented, the Panic.catch expression is ignored and the whole expression results in a panic
• when the Panic.throw 42 sub-expression is not instrumented, the whole expression results in 42 correctly

I created a test reproducing this issue on the wip/db/9402-catch-panic-instrumented branch

[4e6]

The issue might be that we're unwinding too early

enso/engine/runtime-instrument-id-execution/src/main/java/org/enso/interpreter/instrument/id/execution/IdExecutionInstrument.java

Lines 254 to 256 in f05997d

	if (info.isPanic()) {
	throw context.createUnwind(result);
	}

[JaroslavTulach]

The code runs fine from CLI. The project seems to work for me, when "booted". Only later it "diverges from regular run flow":

Yes, the problem is likely in the instrument.

[JaroslavTulach]

The instrument converts PanicException to a sentinel and the catch node then ignores it. The following seems to help:

index 53a716f4fb..6d29469fad 100644
--- engine/runtime/src/main/java/org/enso/interpreter/node/expression/builtin/error/CatchPanicNode.java
+++ engine/runtime/src/main/java/org/enso/interpreter/node/expression/builtin/error/CatchPanicNode.java
@@ -20,6 +20,7 @@ import org.enso.interpreter.runtime.EnsoContext;
 import org.enso.interpreter.runtime.callable.argument.CallArgumentInfo;
 import org.enso.interpreter.runtime.data.atom.AtomNewInstanceNode;
 import org.enso.interpreter.runtime.error.PanicException;
+import org.enso.interpreter.runtime.error.PanicSentinel;
 import org.enso.interpreter.runtime.state.State;
 
 @BuiltinMethod(
@@ -61,7 +62,11 @@ public abstract class CatchPanicNode extends Node {
       @CachedLibrary(limit = "3") InteropLibrary interop) {
     try {
       // Note [Tail call]
-      return thunkExecutorNode.executeThunk(frame, action, state, BaseNode.TailStatus.NOT_TAIL);
+      var ret = thunkExecutorNode.executeThunk(frame, action, state, BaseNode.TailStatus.NOT_TAIL);
+      if (ret instanceof PanicSentinel sentinel) {
+        throw sentinel.getPanic();
+      }
+      return ret;
     } catch (PanicException e) {
       panicBranchProfile.enter();
       Object payload = e.getPayload();

[enso-bot]

Jaroslav Tulach reports a new STANDUP for yesterday (2024-09-26):

Progress: .

• Simple fix for JVM crashes, so we can proceed with release/2024.4: Test parallelism in EnsoParser. Using synchronized to avoid it. #11174 (comment)
• reviewing Kaz's parser changes: Stateless parser API #11147 (comment)
• Fix for It is impossible to catch Panics in the GUI #9402 merged Special treatment of PanicSentinel in CatchPanicNode #11167
• Fix for Two IR objects aren't the same after de-serialization #10985: STRUCTURE_COMPARATOR PR: Use IR.STRUCTURE_COMPARATOR to compare two IR objects #11178
• merging polyglot/java with Pavel's JPMS: 6fdd11c
• deps for std-bits: cfdda7b
• setting up Windows external disk and building Enso
• helping Martha with Windows sbt build (not clean git repo)
• libs standup It should be finished by 2024-09-27.

[enso-bot]

Jaroslav Tulach reports a new STANDUP for yesterday (2024-09-27):

Progress: .

• updating to new IGV: Fixing Enso project classpath while updating to IGV 1.20 #11195
• review of Migrate some passes to Mini passes #11191
• Ydoc expression updates updated Deliver expression updates via Ydoc AST elements #11159
• starting discussion https://discord.com/channels/401396655599124480/1289197532370571356/1289197909107281986
• GraalVM Insight is working in the IDE: Deliver expression updates via Ydoc AST elements #11159 (comment) It should be finished by 2024-09-27.

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