API: Add methods for deprecation + API Folder (#156)

* API: Add methods for deprecation

* API: Deprecated - Lints

* API: Deprecated - PR review amends

addons/mod_loader/api/deprecated.gd

@@ -0,0 +1,34 @@
+class_name ModLoaderDeprecated
+extends Node
+
+# API methods for deprecating funcs. Can be used by mods with public APIs.
+
+const LOG_NAME := "ModLoader:Deprecated"
+
+
+# A method has changed its name/class
+static func deprecated_changed(old_method: String, new_method: String, since_version: String, show_removal_note: bool = true):
+	ModLoaderUtils.log_fatal(str(
+		"DEPRECATED: ",
+		"The method \"%s\" has been deprecated since version %s. " % [old_method, since_version],
+		"Please use \"%s\" instead. " % new_method,
+		"The old method will be removed with the next major update, and will break your code if not changed. " if show_removal_note else ""
+	), LOG_NAME)
+
+
+# A method has been entirely removed, with no replacement
+# (should never be needed but good to have just in case)
+static func deprecated_removed(old_method: String, since_version: String, show_removal_note: bool = true):
+	ModLoaderUtils.log_fatal(str(
+		"DEPRECATED: ",
+		"The method \"%s\" has been deprecated since version %s, and is no longer available. " % [old_method, since_version],
+		"There is currently no replacement method. ",
+		"The method will be removed with the next major update, and will break your code if not changed. " if show_removal_note else ""
+	), LOG_NAME)
+
+
+# Freeform deprecation message.
+# Allows you to add a deprecation comment without specifying the old/new method
+static func deprecated_message(msg: String, since_version: String = ""):
+	var since_text := " (since version %s)" % since_version if since_version else ""
+	ModLoaderUtils.log_fatal(str("DEPRECATED: ", msg, since_text), LOG_NAME)

addons/mod_loader/mod_loader_setup.gd

@@ -40,6 +40,11 @@ const new_global_classes := [
 		"class": "ModLoaderOptionsProfile",
 		"language": "GDScript",
 		"path": "res://addons/mod_loader/options/classes/options_profile.gd"
+	}, {
+		"base": "Node",
+		"class": "ModLoaderDeprecated",
+		"language": "GDScript",
+		"path": "res://addons/mod_loader/api/deprecated.gd"
 	}
 ]