Fix saving generator exception state

Author: msimacek

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/nodes/bytecode/PBytecodeGeneratorRootNode.java

@@ -83,6 +83,15 @@ public PBytecodeGeneratorRootNode(PythonLanguage language, PBytecodeRootNode roo
     @Override
     public Object execute(VirtualFrame frame) {
         calleeContext.enter(frame);
+        MaterializedFrame generatorFrame = PArguments.getGeneratorFrame(frame);
+        /*
+         * This copying of exceptions is necessary because we need to remember the exception state
+         * in the generator, but we don't want to remember the state that is "inherited" from the
+         * outer frame as that can change with each invocation.
+         */
+        PException localException = PArguments.getException(generatorFrame);
+        PException outerException = PArguments.getException(frame);
+        PArguments.setException(frame, localException == null ? outerException : localException);
         Object result;
         try {
             result = rootNode.executeFromBci(frame, resumeBci, resumeStackTop);
@@ -93,10 +102,13 @@ public Object execute(VirtualFrame frame) {
             throw raise.raise(RuntimeError, pe.setCatchingFrameAndGetEscapedException(frame, this), ErrorMessages.GENERATOR_RAISED_STOPITER);
         } finally {
             calleeContext.exit(frame, this);
+            PException exception = PArguments.getException(frame);
+            if (exception != outerException && exception != PException.NO_EXCEPTION) {
+                PArguments.setException(generatorFrame, exception);
+            }
         }
         if (returnProfile.profile(result == null)) {
             // Null result indicates a generator return
-            MaterializedFrame generatorFrame = PArguments.getGeneratorFrame(frame);
             PBytecodeRootNode.FrameInfo info = (PBytecodeRootNode.FrameInfo) generatorFrame.getFrameDescriptor().getInfo();
             Object returnValue = info.getGeneratorReturnValue(generatorFrame);
             if (returnValue != PNone.NONE) {

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/nodes/util/ExceptionStateNodes.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2019, 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2019, 2022, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * The Universal Permissive License (UPL), Version 1.0
@@ -109,8 +109,14 @@ public PException execute(VirtualFrame frame) {
                 if (e == null) {
                     e = PException.NO_EXCEPTION;
                 }
-                // Set into frame to avoid doing the stack walk again
-                PArguments.setException(frame, e);
+                /*
+                 * Set into frame to avoid doing the stack walk again. We cannot do this for
+                 * generators because exception state inherited from outer frame needs to be treated
+                 * differently from local exception state.
+                 */
+                if (PArguments.getGeneratorFrame(frame) == null) {
+                    PArguments.setException(frame, e);
+                }
             }
             return ensure(e);
         }