[4.x] Duplicating a global named script class (i.e. in `script_extension.gd`) causes `"hides a global script class"` error

[ColdCalzone]

In the process of extending a script, this is run:

godot-mod-loader/addons/mod_loader/internal/script_extension.gd

Lines 100 to 106 in e3e795b

	# We want to save scripts for resetting later
	# All the scripts are saved in order already
	if not ModLoaderStore.saved_scripts.has(parent_script_path):
	ModLoaderStore.saved_scripts[parent_script_path] = []
	# The first entry in the saved script array that has the path
	# used as a key will be the duplicate of the not modified script
	ModLoaderStore.saved_scripts[parent_script_path].append(parent_script.duplicate())

This causes an error, Parser Error: Class "ClassName" hides a global script class."

[KANAjetzt]

is this the cause for #338?

[KANAjetzt]

commenting this part out:

static func apply_extension(extension_path: String) -> Script:
	# Check path to file exists
	if not FileAccess.file_exists(extension_path):
		ModLoaderLog.error("The child script path '%s' does not exist" % [extension_path], LOG_NAME)
		return null

	var child_script: Script = ResourceLoader.load(extension_path)
	# Adding metadata that contains the extension script path
	# We cannot get that path in any other way
	# Passing the child_script as is would return the base script path
	# Passing the .duplicate() would return a '' path
	child_script.set_meta("extension_script_path", extension_path)

	# Force Godot to compile the script now.
	# We need to do this here to ensure that the inheritance chain is
	# properly set up, and multiple mods can chain-extend the same
	# class multiple times.
	# This is also needed to make Godot instantiate the extended class
	# when creating singletons.
	# The actual instance is thrown away.
	child_script.new()

	var parent_script: Script = child_script.get_base_script()
	var parent_script_path: String = parent_script.resource_path

	# We want to save scripts for resetting later
	# All the scripts are saved in order already
#	if not ModLoaderStore.saved_scripts.has(parent_script_path):
#		ModLoaderStore.saved_scripts[parent_script_path] = []
#		# The first entry in the saved script array that has the path
#		# used as a key will be the duplicate of the not modified script
#		ModLoaderStore.saved_scripts[parent_script_path].append(parent_script.duplicate())
#
#	ModLoaderStore.saved_scripts[parent_script_path].append(child_script)

	ModLoaderLog.info(
		"Installing script extension: %s <- %s" % [parent_script_path, extension_path], LOG_NAME
	)
	child_script.take_over_path(parent_script_path)

	return child_script

Results in a silent crash for me, in the console this error is logged:

ERROR: FATAL: Condition "!exists" is true.
   at: operator[] (./core/templates/hash_map.h:504)

*Edit
It crashes with the second script_extension in _check_inheritances -> var b_stack := cached_inheritances_stack(extension_b)

godot-mod-loader/addons/mod_loader/internal/script_extension.gd

Line 65 in d5f0733

var parent_script: Script = load(extension_path)

Log dump

Godot Engine v4.1.2.stable.official.399c9dc39 - https://godotengine.org
Vulkan API 1.3.242 - Forward+ - Using Vulkan Device #0: NVIDIA - NVIDIA GeForce RTX 3080
 
INFO ModLoader:Store: Applying options override with feature tag "editor".
DEBUG ModLoader: Autoload order
[
  "ModLoaderStore",
  "ModLoader",
  "Utils",
  "DebugService",
  "SceneManager",
  "TextManager",
  "PartService",
  "EffectService",
  "AudioManager",
  "RunData",
  "PlayerManager",
  "OnlineService",
  "ControllerIcons",
  "InputService",
  "MultiplayerInput"
]
INFO ModLoader: game_install_directory: res://
  Can't open mod folder res://mods
INFO ModLoader: No zipped mods found
SUCCESS ModLoader: DONE: Setup 4 mods
DEBUG ModLoader:UserProfile: Updated the active state of all mods, based on the current user profile "default"
INFO ModLoader:ModData: Loading mod_manifest (manifest.json) for -> GodotModding-ModConfig
DEBUG ModLoader:ModData: GodotModding-ModConfig loaded manifest data -> { "name": "ModConfig", "namespace": "GodotModding", "version_number": "0.1.0", "description": "Example Mod for User Profiles", "website_url": "https://github.com/GodotModding", "dependencies": [], "extra": { "godot": { "authors": ["GodotModding"], "optional_dependencies": [], "compatible_game_version": [], "compatible_mod_loader_version": ["6.0.0"], "incompatibilities": [], "load_before": [], "tags": [], "config_schema": { "title": "Config", "description": "Config for this Mod", "type": "object", "properties": { "material_settings": { "title": "Material Settings", "type": "object", "properties": { "square_scale": { "type": "number", "title": "Square Scale", "minimum": 0, "maximum": 0.3, "multipleOf": 0.001, "default": 0.1 }, "animate": { "type": "boolean", "title": "Animate", "default": false }, "bluer_amount": { "type": "number", "title": "Bluer Amount", "minimum": 0, "maximum": 10, "multipleOf": 0.1, "default": 5.1 }, "mix_amount": { "type": "number", "title": "Mix Amount", "minimum": 0, "maximum": 1, "multipleOf": 0.01, "default": 0.71 }, "color": { "type": "array", "title": "Color Over", "prefixItems": [{ "type": "number", "minimum": 0, "maximum": 255 }, { "type": "number", "minimum": 0, "maximum": 255 }, { "type": "number", "minimum": 0, "maximum": 255 }, { "type": "number", "minimum": 0, "maximum": 255 }], "items": false, "minItems": 3, "maxItems": 4, "default": [0, 0, 0, 255] } } } } }, "description_rich": "", "image": <null> } } }
DEBUG ModLoader:UserProfile: Set the "current_config" of "GodotModding-ModConfig" to "default" in user profile "default" 
INFO ModLoader:ModData: Loading mod_manifest (manifest.json) for -> GodotModding-UserProfile
DEBUG ModLoader:ModData: GodotModding-UserProfile loaded manifest data -> { "name": "UserProfile", "namespace": "GodotModding", "version_number": "0.2.0", "description": "Example Mod for User Profiles", "website_url": "https://github.com/GodotModding", "dependencies": [], "extra": { "godot": { "authors": ["GodotModding"], "optional_dependencies": [], "compatible_game_version": [], "compatible_mod_loader_version": ["6.0.0"], "incompatibilities": [], "load_before": [], "tags": ["test1", "test2"], "config_schema": { "$schema": "https://json-schema.org/draft/2020-12/schema", "title": "Config", "description": "Config for this Mod", "type": "object", "properties": { "select_profile_text": { "title": "Select profile text:", "type": "string", "default": "Select Profile" }, "material_settings": { "title": "Material Settings", "type": "object", "properties": { "square_scale": { "type": "number", "title": "Square Scale", "minimum": 0, "maximum": 0.3, "multipleOf": 0.001, "default": 0.1 }, "animate": { "type": "boolean", "title": "Animate", "default": false }, "blur_amount": { "type": "number", "title": "Blur Amount", "minimum": 0, "maximum": 10, "multipleOf": 0.1, "default": 5.1 }, "mix_amount": { "type": "number", "title": "Mix Amount", "minimum": 0, "maximum": 1, "multipleOf": 0.01, "default": 0.71 }, "color": { "type": "string", "title": "Color Over", "format": "color", "default": "#f7000000" } } } } }, "description_rich": "", "image": <null> } } }
DEBUG ModLoader:UserProfile: Set the "current_config" of "GodotModding-UserProfile" to "test1" in user profile "default" 
INFO ModLoader:ModData: Loading mod_manifest (manifest.json) for -> KANA-VersionNumber
DEBUG ModLoader:ModData: KANA-VersionNumber loaded manifest data -> { "dependencies": [], "description": "Description of your mod...", "extra": { "godot": { "authors": ["KANA"], "compatible_game_version": ["0.0.1"], "compatible_mod_loader_version": ["6.2.0"], "config_schema": {  }, "description_rich": "", "image": <null>, "incompatibilities": [], "load_before": [], "optional_dependencies": [], "tags": [] } }, "name": "VersionNumber", "namespace": "KANA", "version_number": "0.0.1", "website_url": "https://github.com/exampleauthor/examplemod" }
INFO ModLoader:ModData: Loading mod_manifest (manifest.json) for -> KANA-VersionNumber2
DEBUG ModLoader:ModData: KANA-VersionNumber2 loaded manifest data -> { "dependencies": ["KANA-VersionNumber"], "description": "Description of your mod...", "extra": { "godot": { "authors": ["KANA"], "compatible_game_version": ["0.0.1"], "compatible_mod_loader_version": ["6.2.0"], "config_schema": {  }, "description_rich": "", "image": <null>, "incompatibilities": [], "load_before": [], "optional_dependencies": [], "tags": [] } }, "name": "VersionNumber2", "namespace": "KANA", "version_number": "0.0.1", "website_url": "https://github.com/exampleauthor/examplemod" }
SUCCESS ModLoader: DONE: Loaded all meta data
DEBUG ModLoader:Dependency: Checking dependencies - mod_id: GodotModding-ModConfig optional dependencies: []
DEBUG ModLoader:Dependency: Checking dependencies - mod_id: GodotModding-UserProfile optional dependencies: []
DEBUG ModLoader:Dependency: Checking dependencies - mod_id: KANA-VersionNumber optional dependencies: []
DEBUG ModLoader:Dependency: Checking dependencies - mod_id: KANA-VersionNumber2 optional dependencies: []
DEBUG ModLoader:Dependency: Checking dependencies - mod_id: GodotModding-ModConfig required dependencies: []
DEBUG ModLoader:Dependency: Checking dependencies - mod_id: GodotModding-UserProfile required dependencies: []
DEBUG ModLoader:Dependency: Checking dependencies - mod_id: KANA-VersionNumber required dependencies: []
DEBUG ModLoader:Dependency: Checking dependencies - mod_id: KANA-VersionNumber2 required dependencies: ["KANA-VersionNumber"]
DEBUG ModLoader:Dependency: Required dependency -> KANA-VersionNumber importance -> 1
INFO ModLoader: mod_load_order -> 1) KANA-VersionNumber
INFO ModLoader: mod_load_order -> 2) GodotModding-ModConfig
INFO ModLoader: mod_load_order -> 3) GodotModding-UserProfile
INFO ModLoader: mod_load_order -> 4) KANA-VersionNumber2
INFO ModLoader: Initializing -> KANA-VersionNumber
DEBUG ModLoader: Loading script from -> res://mods-unpacked/KANA-VersionNumber/mod_main.gd
DEBUG ModLoader: Loaded script -> <GDScript#-9223371983570336508>
DEBUG ModLoader: Adding child -> KANA-VersionNumber:<Node#53636760837>
INFO ModLoader: Initializing -> GodotModding-ModConfig
DEBUG ModLoader: Loading script from -> res://mods-unpacked/GodotModding-ModConfig/mod_main.gd
DEBUG ModLoader: Loaded script -> <GDScript#-9223371982999911158>
INFO GodotModding-ModConfig: Init
DEBUG ModLoader: Adding child -> GodotModding-ModConfig:<Node#54391735563>
INFO ModLoader: Initializing -> GodotModding-UserProfile
DEBUG ModLoader: Loading script from -> res://mods-unpacked/GodotModding-UserProfile/mod_main.gd
DEBUG ModLoader: Loaded script -> <GDScript#-9223371982194604783>
INFO GodotModding-UserProfile: Init
DEBUG ModLoader: Adding child -> GodotModding-UserProfile:<Node#55280928019>
INFO ModLoader: Initializing -> KANA-VersionNumber2
DEBUG ModLoader: Loading script from -> res://mods-unpacked/KANA-VersionNumber2/mod_main.gd
DEBUG ModLoader: Loaded script -> <GDScript#-9223371981305412328>

*Edit 2:
Basically, as soon as a second script is loaded that extends the same named class as a previous "script_extension," it crashes.

[ColdCalzone]

is this the cause for #338?

Nope. I can recreate that error when directly using take_over_path in a test project.

[KANAjetzt]

Here is a minimal reproduction project that replicates the issue:
Godot v4.1.2.stable.official
Script Extending.zip

As described above, loading the second script that extends the same-named class causes a crash, with the only hint being this error if the editor is run with the console window:

ERROR: FATAL: Condition "!exists" is true.
   at: operator[] (./core/templates/hash_map.h:504)

func _init() -> void:
	var extend_0 = load("res://extends/extend0.gd")
	extend_0.new()
	extend_0.take_over_path("res://base.gd")
	var extend_1 = load("res://extends/extend1.gd")
	extend_1.new()
	extend_1.take_over_path("res://base.gd")

*Edit:
Same result in Godot v4.2.beta1.official

[KANAjetzt]

I opened an issue, let's hope we find answers there 👀
godotengine/godot#83542

I will hunt for a workaround in the meantime. I don't expect that this behavior will change anytime soon. Not being able to extend a script two times renders pretty much the whole mod loader useless.

[ZackeryRSmith]

I will hunt for a workaround in the meantime.

I have limited Godot knowledge but I thought: "why not mess around with this". I'm wondering how feasible it is to modify the file causing errors at runtime. For example modifying extender.gd slightly to remove a line at runtime, fixes the crash.

func _init() -> void:
	var file = FileAccess.open("res://base.gd", FileAccess.READ_WRITE)
	file.seek(0)
	file.store_string(' '.repeat(len("class_name Base")))
	file.close()
	
	var extend_0 = load("res://extends/extend0.gd")
	extend_0.new()
	extend_0.take_over_path("res://base.gd")
	
	var extend_1 = load("res://extends/extend1.gd")
	extend_1.new()
	extend_1.take_over_path("res://base.gd")

However this does create an annoying popup in the editor, but other than that the file seems unaffected. As far as adding back in the functionality of class_name I'm a bit unsure on. You may have to modify the last extension being made to include the class_name? Regardless, I hope this could be of some use!

As an extra note I'm using Godot v4.1.3
Script Extending Workaround.zip

[kakaroto]

The specific issue here doesn't seem to be related to take_over_path but rather to calling parent_script.duplicate() because duplicating the script causes a new (duplicate) script with the same class_name statement, which is why we get the Parser Error: Class "ClassName" hides a global script class." error.
I tried to dynamically update the script's source code, which does fix the duplicate issue. I wanted to assign the class_name to the new child_script, but that causes the same error, since it looks like the global class doesn't get deregistered once we reload the script with the class_name directive.
This is the new code:

	if not ModLoaderStore.saved_scripts.has(parent_script_path):
		ModLoaderStore.saved_scripts[parent_script_path] = []
		# If the parent script has a global class name, then remove it and set it on the child script instead
		# This prevents a "Class X hides a global script class" error when calling duplicate()
		# and (potentially) fixes a take_over_path bug in Godot 4.
		if parent_script.has_source_code() and parent_script is GDScript:
			# Regexp to find a GDScript class name
			var class_name_regex : RegEx = RegEx.create_from_string(r"(?m)^\s*class_name\s+(\S+)")
			var source: String = parent_script.source_code
			var _match: RegExMatch = class_name_regex.search(source)
			if _match:
				var global_name = _match.get_string(1) # Godot 4.3 has parent_script.get_global_name(), but we also don't need to know it
				source = class_name_regex.sub(source, "#$0")
				parent_script.source_code = source
				parent_script.reload()
				# Set the class_name directive on the child instead
                # This doesn't work because the global class is still registered in the engine
				#if child_script.has_source_code():
					#source = _match.get_string(0) + "\n" + child_script.source_code
					#child_script.source_code = source
					#child_script.reload()
		# The first entry in the saved script array that has the path
		# used as a key will be the duplicate of the not modified script
		ModLoaderStore.saved_scripts[parent_script_path].append(parent_script.duplicate())

The idea was to always keep the topmost script with the class_name directive in its source code, and registered as the global class, so remove_specific_extension_from_script would restore things (removing the comment on the line).
Note that Godot 4 doesn't seem to use ProjectSetting _global_script_classes setting anymore, but only has a get_global_class_list method, so we can't register/deregister classes via an API (as far as I could see).

(Unrelated, but this also means that ModLoaderMod.register_global_classes_from_array doesn't work anymore, i.e: #335)