{LYN-4372} fix for Python exit crash (#1600)

There is a crash when sys.exit() was being called since embedded Python
should not have control of the application lifetime. The Py_InspectFlag
puts the Python VM into 'inspection mode' which prevents the app
shutdown when any sys.exit() is invoked.

Notes:
* skips 'regset' extra command line in PythonBindingsExample
* added methods for handling PythonBindingsExample errors

Test: added Application_SystemExit_Blocked and
fixed up Application_Run_Fails now is Application_Run_Works

Code/Tools/PythonBindingsExample/source/Application.h

@@ -28,6 +28,18 @@ namespace PythonBindingsExample
         void TearDown();
         bool RunWithParameters(const ApplicationParameters& params);
 
+        inline void GetErrorCount(int& exceptionCount, int& errorCount)
+        {
+            exceptionCount = m_pythonExceptionCount;
+            errorCount = m_pythonErrorCount;
+        }
+
+        inline void ResetErrorCount()
+        {
+            m_pythonExceptionCount = 0;
+            m_pythonErrorCount = 0;
+        }
+
     protected:
         ////////////////////////////////////////////////////////////////////////////////////////////
         // TraceMessageBus

Code/Tools/PythonBindingsExample/source/ApplicationParameters.cpp

@@ -60,6 +60,10 @@ PythonBindingsExample.exe --file path/to/file.py --arg one --arg two
             {
                 m_interactiveMode = true;
             }
+            else if (switchItem.m_option.starts_with("regset"))
+            {
+                // skip
+            }
             else
             {
                 AZ_Warning("python_app", false, "Unknown switch %s \n", switchItem.m_option.c_str());

Code/Tools/PythonBindingsExample/tests/ApplicationTests.cpp

@@ -58,9 +58,9 @@ namespace PythonBindingsExample
 
     AZStd::unique_ptr<PythonBindingsExample::Application> PythonBindingsExampleTest::s_application;
 
-    TEST_F(PythonBindingsExampleTest, Application_Run_Fails)
+    TEST_F(PythonBindingsExampleTest, Application_Run_Works)
     {
-        EXPECT_FALSE(s_application->Run());
+        EXPECT_TRUE(s_application->Run());
     }
 
     TEST_F(PythonBindingsExampleTest, Application_RunWithParameters_Works)
@@ -90,4 +90,37 @@ namespace PythonBindingsExample
         EXPECT_TRUE(s_application->RunWithParameters(params));
     }
 
+    TEST_F(PythonBindingsExampleTest, Application_SystemExit_Blocked)
+    {
+        int exceptions = 0;
+        int errors = 0;
+
+        s_application->GetErrorCount(exceptions, errors);
+        ASSERT_EQ(exceptions, 0);
+        ASSERT_EQ(errors, 0);
+
+        // expects a clean "error" from this statement
+        // the whole program should not exit()
+        {
+            ApplicationParameters params;
+            params.m_pythonStatement = "import sys; sys.exit(0)";
+            EXPECT_FALSE(s_application->RunWithParameters(params));
+
+            s_application->GetErrorCount(exceptions, errors);
+            EXPECT_EQ(exceptions, 0);
+            EXPECT_GE(errors, 1);
+        }
+        s_application->ResetErrorCount();
+
+        // should be able to run more statements
+        {
+            ApplicationParameters params;
+            params.m_pythonStatement = "import sys";
+            EXPECT_TRUE(s_application->RunWithParameters(params));
+
+            s_application->GetErrorCount(exceptions, errors);
+            EXPECT_EQ(exceptions, 0);
+            EXPECT_EQ(errors, 0);
+        }
+    }
 }

Gems/EditorPythonBindings/Code/Source/PythonSystemComponent.cpp

@@ -496,6 +496,7 @@ namespace EditorPythonBindings
             // ignore system location for sites site-packages
             Py_IsolatedFlag = 1; // -I - Also sets Py_NoUserSiteDirectory.  If removed PyNoUserSiteDirectory should be set.
             Py_IgnoreEnvironmentFlag = 1; // -E
+            Py_InspectFlag = 1; // unhandled SystemExit will terminate the process unless Py_InspectFlag is set
 
             const bool initializeSignalHandlers = true;
             pybind11::initialize_interpreter(initializeSignalHandlers);