Construct plugins with a static fromContext (#487)

Each plugin class now has a private constructor and a static async
fromContext(context) that loads its datastores, constructs the instance
and attaches its handlers and hooks. This replaces the public constructor
followed by init(), and AutoRestart's start().

Datastores are loaded before construction and passed to the constructor,
so the definite assignment assertions on them are gone. Tests build the
plugins through fromContext and pass a wrapped logger in the context
instead of overwriting plugin.logger before init().

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

exp_groups/instance.ts

@@ -18,9 +18,6 @@ export type IpcPlayerAssignments = {
 };
 
 export class InstancePlugin {
-    instance: Instance;
-    logger: lib.Logger;
-    name: string;
     // Once only, don't send permissions for these groups
     // This is used for groups created on this instance that only need the controller generated id
     skipSendingPermissions = new Set<string>(); 
@@ -29,23 +26,27 @@ export class InstancePlugin {
     // Track known online players so that we only apply assignment updates for them
     onlinePlayers = new Set<string>();
 
-    constructor(context: InstancePluginContext) {
-        this.instance = context.instance;
-        this.logger = context.logger;
-        this.name = context.plugin.name;
-    }
+    private constructor(
+        public instance: Instance,
+        public logger: lib.Logger,
+        public name: string,
+    ) {}
 
-    async init() {
-        this.instance.handle(messages.GroupUpdatedEvent, this.handleGroupUpdatedEvent.bind(this));
-        this.instance.handle(messages.ResolvedAssignmentUpdatedEvent, this.handleResolvedAssignmentUpdatedEvent.bind(this));
-        this.instance.server.handle(`exp_group:group_updated`, this.handleGroupUpdatedIPC.bind(this))
-        this.instance.server.handle(`exp_group:group_deleted`, this.handleGroupDeletedIPC.bind(this))
-        this.instance.server.handle(`exp_group:player_assignments`, this.handlePlayerAssignmentsIPC.bind(this))
+    static async fromContext(context: InstancePluginContext) {
+        const instance = context.instance;
+        const plugin = new InstancePlugin(instance, context.logger, context.plugin.name);
 
-        const hooks = this.instance.hooks;
-        hooks.instanceConfigFieldChanged.attach(this.name, this.onInstanceConfigFieldChanged.bind(this));
-        hooks.start.attach(this.name, this.onStart.bind(this));
-        hooks.playerEvent.attach(this.name, this.onPlayerEvent.bind(this));
+        instance.handle(messages.GroupUpdatedEvent, plugin.handleGroupUpdatedEvent.bind(plugin));
+        instance.handle(messages.ResolvedAssignmentUpdatedEvent, plugin.handleResolvedAssignmentUpdatedEvent.bind(plugin));
+        instance.server.handle(`exp_group:group_updated`, plugin.handleGroupUpdatedIPC.bind(plugin))
+        instance.server.handle(`exp_group:group_deleted`, plugin.handleGroupDeletedIPC.bind(plugin))
+        instance.server.handle(`exp_group:player_assignments`, plugin.handlePlayerAssignmentsIPC.bind(plugin))
+
+        const hooks = instance.hooks;
+        hooks.instanceConfigFieldChanged.attach(plugin.name, plugin.onInstanceConfigFieldChanged.bind(plugin));
+        hooks.start.attach(plugin.name, plugin.onStart.bind(plugin));
+        hooks.playerEvent.attach(plugin.name, plugin.onPlayerEvent.bind(plugin));
+        return plugin;
     }
 
     async onInstanceConfigFieldChanged(field: string, curr: unknown, prev: unknown) {
@@ -185,5 +186,5 @@ export class InstancePlugin {
 }
 
 export default async function (context: InstancePluginContext) {
-    await new InstancePlugin(context).init();
+    await InstancePlugin.fromContext(context);
 }