correct fix for bug #23871, __main__ module was being overwritten in nested functions, so on returning from calling operators the __main__ module could be cleared and imported modules turn into None

calling
  bpy.ops.wm.read_factory_settings()
... would clear a scripts namespace if running directly, not in a module.


Fix by backing up and restoring the __main__ module.

Also found BKE_reportf wasnt printing all reports in background mode as BKE_report() was doing.

source/blender/python/generic/py_capi_utils.c

@@ -282,6 +282,10 @@ PyObject *PyC_UnicodeFromByte(const char *str)
   for 'pickle' to work as well as strings like this...
  >> foo = 10
  >> print(__import__("__main__").foo)
+*
+* note: this overwrites __main__ which gives problems with nested calles.
+* be sure to run PyC_MainModule_Backup & PyC_MainModule_Restore if there is
+* any chance that python is in the call stack.
 *****************************************************************************/
 PyObject *PyC_DefaultNameSpace(const char *filename)
 {
@@ -297,6 +301,20 @@ PyObject *PyC_DefaultNameSpace(const char *filename)
 	return PyModule_GetDict(mod_main);
 }
 
+/* restore MUST be called after this */
+void PyC_MainModule_Backup(PyObject **main_mod)
+{
+	PyInterpreterState *interp= PyThreadState_GET()->interp;
+	*main_mod= PyDict_GetItemString(interp->modules, "__main__");
+	Py_XINCREF(*main_mod); /* dont free */
+}
+
+void PyC_MainModule_Restore(PyObject *main_mod)
+{
+	PyInterpreterState *interp= PyThreadState_GET()->interp;
+	PyDict_SetItemString(interp->modules, "__main__", main_mod);
+	Py_XDECREF(main_mod);
+}
 
 /* Would be nice if python had this built in */
 void PyC_RunQuicky(const char *filepath, int n, ...)

source/blender/python/generic/py_capi_utils.h

@@ -39,4 +39,7 @@ const char *	PyC_UnicodeAsByte(PyObject *py_str, PyObject **coerce); /* coerce m
 /* name namespace function for bpy & bge */
 PyObject *		PyC_DefaultNameSpace(const char *filename);
 void			PyC_RunQuicky(const char *filepath, int n, ...);
+
+void PyC_MainModule_Backup(PyObject **main_mod);
+void PyC_MainModule_Restore(PyObject *main_mod);
 #endif // PY_CAPI_UTILS_H

source/blender/python/intern/bpy_interface.c

@@ -328,6 +328,7 @@ typedef struct {
 
 static int python_script_exec(bContext *C, const char *fn, struct Text *text, struct ReportList *reports)
 {
+	PyObject *main_mod= NULL;
 	PyObject *py_dict= NULL, *py_result= NULL;
 	PyGILState_STATE gilstate;
 
@@ -339,6 +340,8 @@ static int python_script_exec(bContext *C, const char *fn, struct Text *text, st
 
 	bpy_context_set(C, &gilstate);
 
+	PyC_MainModule_Backup(&main_mod);
+
 	if (text) {
 		char fn_dummy[FILE_MAXDIR];
 		bpy_text_filename_get(fn_dummy, text);
@@ -413,10 +416,10 @@ static int python_script_exec(bContext *C, const char *fn, struct Text *text, st
 #endif
 
 #undef PYMODULE_CLEAR_WORKAROUND
-		/* normal */
-		PyDict_SetItemString(PyThreadState_GET()->interp->modules, "__main__", Py_None);
 	}
 
+	PyC_MainModule_Restore(main_mod);
+
 	bpy_context_clear(C, &gilstate);
 
 	return (py_result != NULL);
@@ -446,6 +449,7 @@ int BPY_button_exec(bContext *C, const char *expr, double *value)
 	PyGILState_STATE gilstate;
 	PyObject *py_dict, *mod, *retval;
 	int error_ret = 0;
+	PyObject *main_mod= NULL;
 	
 	if (!value || !expr) return -1;
 
@@ -455,7 +459,9 @@ int BPY_button_exec(bContext *C, const char *expr, double *value)
 	}
 
 	bpy_context_set(C, &gilstate);
-	
+
+	PyC_MainModule_Backup(&main_mod);
+
 	py_dict= PyC_DefaultNameSpace("<blender button>");
 
 	mod = PyImport_ImportModule("math");
@@ -506,7 +512,7 @@ int BPY_button_exec(bContext *C, const char *expr, double *value)
 		BPy_errors_to_report(CTX_wm_reports(C));
 	}
 
-	PyDict_SetItemString(PyThreadState_GET()->interp->modules, "__main__", Py_None);
+	PyC_MainModule_Backup(&main_mod);
 	
 	bpy_context_clear(C, &gilstate);
 	
@@ -516,6 +522,7 @@ int BPY_button_exec(bContext *C, const char *expr, double *value)
 int BPY_string_exec(bContext *C, const char *expr)
 {
 	PyGILState_STATE gilstate;
+	PyObject *main_mod= NULL;
 	PyObject *py_dict, *retval;
 	int error_ret = 0;
 
@@ -527,6 +534,8 @@ int BPY_string_exec(bContext *C, const char *expr)
 
 	bpy_context_set(C, &gilstate);
 
+	PyC_MainModule_Backup(&main_mod);
+
 	py_dict= PyC_DefaultNameSpace("<blender string>");
 
 	retval = PyRun_String(expr, Py_eval_input, py_dict, py_dict);
@@ -540,8 +549,8 @@ int BPY_string_exec(bContext *C, const char *expr)
 		Py_DECREF(retval);
 	}
 
-	PyDict_SetItemString(PyThreadState_GET()->interp->modules, "__main__", Py_None);
-	
+	PyC_MainModule_Restore(main_mod);
+
 	bpy_context_clear(C, &gilstate);
 	
 	return error_ret;