Can't continue after finishing quest then quitting from Fray's End

[wjt]

Description

Steps to reproduce:

1. Start a new game
2. Embark on a quest
3. Complete the quest
4. In Fray's End, interact with the Eternal Loom
5. Complete three rounds of Sokoban (hint: hit reset 5 times then hit skip)
6. In Fray's End, click through the “Thank you, StoryWeaver! The fabric of the world slowly heals!” dialogue, then press Pause, Exit to Title
7. On the title screen, pick Continue

Expected result:

The title screen fades out, and the game resumes from Fray's End.

Actual result:

The title screen is displayed again.

The following errors are shown in the Debugger tab:

E 0:00:05:409   _load: Resource file not found: res:// (expected type: unknown)
  <C++ Error>   Method/function failed. Returning: Ref<Resource>()
  <C++ Source>  core/io/resource_loader.cpp:351 @ _load()
E 0:00:06:393   scene_switcher.gd:144 @ change_to_packed(): Can't change to a null scene. Use unload_current_scene() if you wish to unload it.
  <C++ Error>   Required object "rp_scene" is null.
  <C++ Source>  scene/main/scene_tree.cpp:1688 @ change_scene_to_packed()
  <Stack Trace> scene_switcher.gd:144 @ change_to_packed()
                scene_switcher.gd:113 @ <anonymous lambda>()
                transitions.gd:92 @ do_transition()
                transitions.gd:72 @ _leave_scene()
                transitions.gd:63 @ _do_tween()

XP Summary (total 275)

Subdomain	Skill	XP
Engineering: Gameplay & Systems Programming	Problem Solving	75
Engineering: Gameplay & Systems Programming	Creativity & Design Thinking	50
Engineering: Gameplay & Systems Programming	Technical Literacy	150

[wjt]

game state:

https://gist.github.com/wjt/0024758a8dfa995b47243b1236ccf4d7

Here's what I think is happening:

1. When returning to Fray's End in step 6, eternal_loom.gd calls GameState.mark_quest_completed():

threadbare/scenes/game_elements/props/eternal_loom/components/eternal_loom.gd

Line 46 in bd01765

GameState.mark_quest_completed()

2. mark_quest_completed() calls _clear_quest_state():

threadbare/scenes/globals/game_state/game_state.gd

Lines 193 to 202 in bd01765

	func mark_quest_completed() -> void:
	if current_quest:
	var quest_name := current_quest.resource_path
	if quest_name not in completed_quests:
	completed_quests.append(quest_name)
	_state.set_value(GLOBAL_SECTION, COMPLETED_QUESTS_KEY, completed_quests)
	current_quest = null
	_clear_quest_state()
	_save()

3. _clear_quest_state() erases the entire [quest] section of the game state:

threadbare/scenes/globals/game_state/game_state.gd

Lines 185 to 188 in bd01765

	## Clear all quest-related state from the config file.
	func _clear_quest_state() -> void:
	if _state.has_section(QUEST_SECTION):
	_state.erase_section(QUEST_SECTION)

4. The current scene is stored in the [quest] section. So GameState.restore() returns a dictionary whose "scene_path" key is empty string:

threadbare/scenes/globals/game_state/game_state.gd

Lines 315 to 339 in bd01765

	## Restore the persisted state.
	func restore() -> Dictionary:
	inventory.clear()
	for item_type: InventoryItem.ItemType in _state.get_value(
	INVENTORY_SECTION, INVENTORY_ITEMS_KEY, []
	):
	var item := InventoryItem.with_type(item_type)
	inventory.append(item)
	if _state.has_section_key(QUEST_SECTION, QUEST_PATH_KEY):
	current_quest = load(_state.get_value(QUEST_SECTION, QUEST_PATH_KEY)) as Quest
	var scene_path: String = _state.get_value(QUEST_SECTION, QUEST_CURRENTSCENE_KEY, "")
	current_spawn_point = _state.get_value(QUEST_SECTION, QUEST_SPAWNPOINT_KEY, ^"")
	incorporating_threads = _state.get_value(
	GLOBAL_SECTION, GLOBAL_INCORPORATING_THREADS_KEY, false
	)
	completed_quests = _state.get_value(GLOBAL_SECTION, COMPLETED_QUESTS_KEY, [] as Array[String])
	# Restore lives from saved state, default to MAX_LIVES if not found
	current_lives = _state.get_value(GLOBAL_SECTION, LIVES_KEY, MAX_LIVES)
	if DEBUG_LIVES:
	prints("[LIVES DEBUG] State restored. Lives:", current_lives)
	return {"scene_path": scene_path, "spawn_point": current_spawn_point}

5. And so the main menu tries to change scene to "":

threadbare/scenes/menus/title/components/title_screen.gd

Lines 17 to 27 in bd01765

	func _on_main_menu_continue_pressed() -> void:
	var saved_scene: Dictionary = GameState.restore()
	(
	SceneSwitcher
	. change_to_file_with_transition(
	saved_scene["scene_path"],
	saved_scene["spawn_point"],
	Transition.Effect.FADE,
	Transition.Effect.FADE,
	)
	)

[wjt]

IMO the bug is that the current scene is stored in the quest state, but it should instead be [global].

This problem does not occur if you abandon a quest, because immediately after clearing the quest state via GameState.abandon_quest(), the scene is changed to Fray's End, setting that field again:

threadbare/scenes/globals/pause/pause_overlay.gd

Lines 35 to 40 in bd01765

	func _on_abandon_quest_pressed() -> void:
	toggle_pause()
	GameState.abandon_quest()
	SceneSwitcher.change_to_file_with_transition(
	frays_end, ^"", Transition.Effect.FADE, Transition.Effect.FADE
	)

[wjt]

Turns out I need to fix this while prototyping a change in #2021