Add sys.exception()

Fixes #467

Author: msimacek

graalpython/com.oracle.graal.python.test/src/tests/unittest_tags/test_sys.txt

@@ -1,6 +1,9 @@
 test.test_sys.ActiveExceptionTests.test_exc_info_no_exception @ darwin-arm64,darwin-x86_64,linux-aarch64,linux-x86_64,win32-AMD64
 test.test_sys.ActiveExceptionTests.test_exc_info_with_exception_instance @ darwin-arm64,darwin-x86_64,linux-aarch64,linux-x86_64,win32-AMD64
 test.test_sys.ActiveExceptionTests.test_exc_info_with_exception_type @ darwin-arm64,darwin-x86_64,linux-aarch64,linux-x86_64,win32-AMD64
+test.test_sys.ActiveExceptionTests.test_sys_exception_no_exception @ linux-x86_64
+test.test_sys.ActiveExceptionTests.test_sys_exception_with_exception_instance @ linux-x86_64
+test.test_sys.ActiveExceptionTests.test_sys_exception_with_exception_type @ linux-x86_64
 test.test_sys.DisplayHookTest.test_custom_displayhook @ darwin-arm64,darwin-x86_64,linux-aarch64,linux-x86_64,win32-AMD64
 test.test_sys.DisplayHookTest.test_lost_displayhook @ darwin-arm64,darwin-x86_64,linux-aarch64,linux-x86_64,win32-AMD64
 test.test_sys.DisplayHookTest.test_original_displayhook @ darwin-arm64,darwin-x86_64,linux-aarch64,linux-x86_64,win32-AMD64

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/modules/SysModuleBuiltins.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2017, 2025, 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
@@ -863,6 +863,25 @@ static PTuple run(VirtualFrame frame,
         }
     }
 
+    @Builtin(name = "exception", needsFrame = true)
+    @GenerateNodeFactory
+    abstract static class ExceptionNode extends PythonBuiltinNode {
+
+        @Specialization
+        static Object run(VirtualFrame frame,
+                        @Bind("this") Node inliningTarget,
+                        @Cached GetEscapedExceptionNode getEscapedExceptionNode,
+                        @Cached GetCaughtExceptionNode getCaughtExceptionNode) {
+            AbstractTruffleException currentException = getCaughtExceptionNode.execute(frame);
+            assert currentException != PException.NO_EXCEPTION;
+            if (currentException == null) {
+                return PNone.NONE;
+            } else {
+                return getEscapedExceptionNode.execute(inliningTarget, currentException);
+            }
+        }
+    }
+
     // ATTENTION: this is intentionally a PythonBuiltinNode and not PythonUnaryBuiltinNode,
     // because we need a guarantee that this builtin will get its own stack frame in order to
     // be able to count how many frames down the call stack we need to walk