feat(core): add snapshot mode to lifecycle (stop after didLoad phase)

Add `snapshot` option to EggCoreOptions and LifecycleOptions.
When enabled, lifecycle stops after didLoad phase completes,
skipping willReady, didReady, and serverDidReady hooks.
Used for V8 startup snapshot construction.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: killagu

packages/core/src/egg.ts

@@ -33,6 +33,12 @@ export interface EggCoreOptions {
   env?: string;
   /** Skip lifecycle hooks, only trigger loadMetadata for manifest generation */
   metadataOnly?: boolean;
+  /**
+   * When true, the application loads metadata only (plugins, configs, extensions,
+   * services, controllers) without starting servers, timers, or connections.
+   * Used for V8 startup snapshot construction.
+   */
+  snapshot?: boolean;
 }
 
 export type EggCoreInitOptions = Partial<EggCoreOptions>;
@@ -191,6 +197,7 @@ export class EggCore extends KoaApplication {
       baseDir: options.baseDir,
       app: this,
       logger: this.console,
+      snapshot: options.snapshot,
     });
     this.lifecycle.on('error', (err) => this.emit('error', err));
     this.lifecycle.on('ready_timeout', (id) => this.emit('ready_timeout', id));

packages/core/src/lifecycle.ts

@@ -69,6 +69,12 @@ export interface LifecycleOptions {
   baseDir: string;
   app: EggCore;
   logger: EggConsoleLogger;
+  /**
+   * When true, the lifecycle stops after didLoad phase completes.
+   * willReady, didReady, and serverDidReady hooks are NOT called.
+   * Used for V8 startup snapshot construction.
+   */
+  snapshot?: boolean;
 }
 
 export type FunWithFullPath = Fun & { fullPath?: string };
@@ -119,7 +125,7 @@ export class Lifecycle extends EventEmitter {
     });
 
     this.ready((err) => {
-      if (!this.#metadataOnly) {
+      if (!this.#metadataOnly && !this.options.snapshot) {
         void this.triggerDidReady(err);
       }
       debug('app ready');
@@ -372,6 +378,10 @@ export class Lifecycle extends EventEmitter {
       debug('trigger didLoad end');
       if (err) {
         this.ready(err);
+      } else if (this.options.snapshot) {
+        // In snapshot mode, stop after didLoad — skip willReady/didReady/serverDidReady
+        debug('snapshot mode: skipping willReady, marking ready after didLoad');
+        this.ready(true);
       } else {
         this.triggerWillReady();
       }