Fix saving a quit.blend on exit when a file failed to load

When a file passed in from the command line failed to load,
blender would exit & save the quit.blend.

Resolve by adding a `do_user_exit_actions` to WM_exit_ex which is
false in backgrounds mode or when an error has occurred.

source/blender/python/intern/bpy_interface_atexit.c

@@ -22,7 +22,7 @@ static PyObject *bpy_atexit(PyObject *UNUSED(self), PyObject *UNUSED(args), PyOb
   /* close down enough of blender at least not to crash */
   struct bContext *C = BPY_context_get();
 
-  WM_exit_ex(C, false);
+  WM_exit_ex(C, false, false);
 
   Py_RETURN_NONE;
 }

source/blender/windowmanager/WM_api.h

@@ -100,9 +100,17 @@ void WM_init_input_devices(void);
  */
 void WM_init(struct bContext *C, int argc, const char **argv);
 /**
+ * \param do_python: Free all data associated with Blender's Python integration.
+ * Also exit the Python interpreter (unless `WITH_PYTHON_MODULE` is enabled).
+ * \param do_user_exit_actions: When enabled perform actions associated with a user
+ * having been using Blender then exiting. Actions such as writing the auto-save
+ * and writing any changes to preferences.
+ * Set to false in background mode or when exiting because of failed command line argument parsing.
+ * In general automated actions where the user isn't making changes should pass in false too.
+ *
  * \note doesn't run exit() call #WM_exit() for that.
  */
-void WM_exit_ex(struct bContext *C, bool do_python);
+void WM_exit_ex(struct bContext *C, bool do_python, bool do_user_exit_actions);
 
 /**
  * \brief Main exit function to close Blender ordinarily.
@@ -111,6 +119,8 @@ void WM_exit_ex(struct bContext *C, bool do_python);
  *
  * \param exit_code: Passed to #exit, typically #EXIT_SUCCESS or #EXIT_FAILURE should be used.
  * With failure being used for an early exit when parsing command line arguments fails.
+ * Note that any exit-code besides #EXIT_SUCCESS calls #WM_exit_ex with its `do_user_exit_actions`
+ * argument set to false.
  */
 void WM_exit(struct bContext *C, int exit_code) ATTR_NORETURN;
 

source/blender/windowmanager/intern/wm_init_exit.cc

@@ -472,15 +472,21 @@ void wm_exit_schedule_delayed(const bContext *C)
 
 void UV_clipboard_free();
 
-void WM_exit_ex(bContext *C, const bool do_python)
+void WM_exit_ex(bContext *C, const bool do_python, const bool do_user_exit_actions)
 {
   wmWindowManager *wm = C ? CTX_wm_manager(C) : nullptr;
 
+  /* While nothing technically prevents saving user data in background mode,
+   * don't do this as not typically useful and more likely to cause problems
+   * if automated scripts happen to write changes to the preferences for e.g.
+   * Saving #BLENDER_QUIT_FILE is also not likely to be desired either. */
+  BLI_assert(G.background ? (do_user_exit_actions == false) : true);
+
   /* first wrap up running stuff, we assume only the active WM is running */
   /* modal handlers are on window level freed, others too? */
   /* NOTE: same code copied in `wm_files.cc`. */
   if (C && wm) {
-    if (!G.background) {
+    if (do_user_exit_actions) {
       struct MemFile *undo_memfile = wm->undo_stack ?
                                          ED_undosys_stack_memfile_get_active(wm->undo_stack) :
                                          nullptr;
@@ -514,7 +520,7 @@ void WM_exit_ex(bContext *C, const bool do_python)
       ED_screen_exit(C, win, WM_window_get_active_screen(win));
     }
 
-    if (!G.background) {
+    if (do_user_exit_actions) {
       if ((U.pref_flag & USER_PREF_FLAG_SAVE) && ((G.f & G_FLAG_USERPREF_NO_SAVE_ON_EXIT) == 0)) {
         if (U.runtime.is_dirty) {
           BKE_blendfile_userdef_write_all(nullptr);
@@ -692,7 +698,8 @@ void WM_exit_ex(bContext *C, const bool do_python)
 
 void WM_exit(bContext *C, const int exit_code)
 {
-  WM_exit_ex(C, true);
+  const bool do_user_exit_actions = G.background ? (exit_code == EXIT_SUCCESS) : false;
+  WM_exit_ex(C, true, do_user_exit_actions);
 
   printf("\nBlender quit\n");
 

source/creator/creator.c

@@ -594,7 +594,7 @@ int main(int argc,
 #ifdef WITH_PYTHON_MODULE
 void main_python_exit(void)
 {
-  WM_exit_ex((bContext *)evil_C, true);
+  WM_exit_ex((bContext *)evil_C, true, false);
   evil_C = NULL;
 }
 #endif