Add version to block script data

In the plugin, add a new constant for the current data version. This
will start in 0 and be bumped each time the data format changes.

In the BlockScriptData resource, add an integer version field which
defaults to zero. The version will be set to the current version when
the resource is saved.

The actual migration is TBD. Only a warning is printed for now.

https://phabricator.endlessm.com/T35547

Author: manuq

addons/block_code/block_script_data/block_script_data.gd

@@ -4,9 +4,11 @@ extends Resource
 @export var script_inherits: String
 @export var block_trees: SerializedBlockTreeNodeArray
 @export var generated_script: String
+@export var version: int
 
 
-func _init(p_script_inherits: String = "", p_block_trees: SerializedBlockTreeNodeArray = null, p_generated_script: String = ""):
+func _init(p_script_inherits: String = "", p_block_trees: SerializedBlockTreeNodeArray = null, p_generated_script: String = "", p_version = 0):
 	script_inherits = p_script_inherits
 	block_trees = p_block_trees
 	generated_script = p_generated_script
+	version = p_version

addons/block_code/ui/constants.gd

@@ -1,5 +1,7 @@
 extends Object
 
+const CURRENT_DATA_VERSION = 0
+
 const KNOB_X = 10.0
 const KNOB_W = 20.0
 const KNOB_H = 5.0

addons/block_code/ui/main_panel.gd

@@ -15,6 +15,8 @@ extends Control
 @onready var _icon_collapse := EditorInterface.get_editor_theme().get_icon("Back", "EditorIcons")
 @onready var _icon_expand := EditorInterface.get_editor_theme().get_icon("Forward", "EditorIcons")
 
+const Constants = preload("res://addons/block_code/ui/constants.gd")
+
 var _current_block_code_node: BlockCode
 var _block_code_nodes: Array
 var _collapsed: bool = false
@@ -82,6 +84,14 @@ func _on_delete_dialog_confirmed(block_code_node: BlockCode):
 	undo_redo.commit_action()
 
 
+func _try_migration():
+	var version: int = _current_block_code_node.block_script.version
+	if version == Constants.CURRENT_DATA_VERSION:
+		# No migration needed.
+		return
+	push_warning("Migration not implemented from %d to %d" % [version, Constants.CURRENT_DATA_VERSION])
+
+
 func switch_scene(scene_root: Node):
 	_title_bar.scene_selected(scene_root)
 
@@ -90,6 +100,8 @@ func switch_block_code_node(block_code_node: BlockCode):
 	var block_script: BlockScriptData = block_code_node.block_script if block_code_node else null
 	_current_block_code_node = block_code_node
 	_delete_node_button.disabled = _current_block_code_node == null
+	if _current_block_code_node != null:
+		_try_migration()
 	_picker.bsd_selected(block_script)
 	_title_bar.bsd_selected(block_script)
 	_block_canvas.bsd_selected(block_script)
@@ -129,6 +141,7 @@ func save_script():
 	var generated_script = _block_canvas.generate_script_from_current_window(block_script.script_inherits)
 	block_script.block_trees = block_trees
 	block_script.generated_script = generated_script
+	block_script.version = Constants.CURRENT_DATA_VERSION
 
 	undo_redo.add_do_property(_current_block_code_node.block_script, "block_trees", block_trees)
 	undo_redo.add_do_property(_current_block_code_node.block_script, "generated_script", generated_script)