fix: remove delegates from Context (#15)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

## Release Notes

- **Documentation**
- Updated documentation for Koa `Response` object, adding method to
append headers

- **Dependencies**
  - Removed `delegates` dependency
  - Added `@eggjs/bin`
  - Updated `@types/node` and `mm` dependency versions

- **Type Improvements**
- Enhanced type safety across `Application`, `Context`, `Request`, and
`Response` classes
  - Introduced more flexible generic type handling

- **Code Refactoring**
  - Removed delegation mechanism in `Context` class
- Added direct method and property definitions for request and response
handling

- **Testing**
- Added new test cases for context subclassing and application behavior

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

docs/api/response.md

@@ -14,7 +14,6 @@
 
   Response header object. Alias as `response.header`.
 
-
 ### response.socket
 
   Response socket. Points to net.Socket instance as `request.socket`.
@@ -214,6 +213,7 @@ ctx.set('Cache-Control', 'no-cache');
 ```
 
 ### response.append(field, value)
+
   Append additional header `field` with value `val`.
 
 ```js

example/extend/middleware.ts

@@ -1,4 +1,4 @@
-import { MiddlewareFunc, Context, type ContextDelegation } from '../../src/index.js';
+import { MiddlewareFunc, Context } from '../../src/index.js';
 
 class CustomContext extends Context {
   // Add your custom properties and methods here
@@ -7,9 +7,7 @@ class CustomContext extends Context {
   }
 }
 
-type ICustomContext = CustomContext & ContextDelegation;
-
-export const middleware: MiddlewareFunc<ICustomContext> = async (ctx, next) => {
+export const middleware: MiddlewareFunc<CustomContext> = async (ctx, next) => {
   console.log('middleware start, %s', ctx.hello, ctx.writable);
   await next();
   console.log('middleware end');

package.json

@@ -9,8 +9,11 @@
   },
   "description": "Koa web app framework for https://eggjs.org",
   "scripts": {
-    "test": "npm run lint -- --fix && egg-bin test",
-    "ci": "npm run lint && egg-bin cov && npm run prepublishOnly && attw --pack",
+    "pretest": "npm run lint -- --fix",
+    "test": "egg-bin test",
+    "preci": "npm run lint",
+    "ci": "egg-bin cov",
+    "postci": "npm run prepublishOnly && attw --pack",
     "lint": "eslint src test --cache",
     "authors": "git log --format='%aN <%aE>' | sort -u > AUTHORS",
     "prepublishOnly": "tshy && tshy-after"
@@ -35,7 +38,6 @@
     "content-disposition": "~0.5.4",
     "content-type": "^1.0.5",
     "cookies": "^0.9.1",
-    "delegates": "^1.0.0",
     "destroy": "^1.0.4",
     "encodeurl": "^1.0.2",
     "escape-html": "^1.0.3",
@@ -53,12 +55,12 @@
   },
   "devDependencies": {
     "@arethetypeswrong/cli": "^0.17.1",
+    "@eggjs/bin": "^7.0.1",
     "@eggjs/tsconfig": "^1.3.3",
     "@types/accepts": "^1.3.7",
     "@types/content-disposition": "^0.5.8",
     "@types/content-type": "^1.1.8",
     "@types/cookies": "^0.9.0",
-    "@types/delegates": "^1.0.3",
     "@types/destroy": "^1.0.3",
     "@types/encodeurl": "^1.0.2",
     "@types/escape-html": "^1.0.4",
@@ -67,17 +69,16 @@
     "@types/http-errors": "^2.0.4",
     "@types/koa-compose": "^3.2.8",
     "@types/mocha": "^10.0.1",
-    "@types/node": "^20.2.5",
+    "@types/node": "22",
     "@types/on-finished": "^2.3.4",
     "@types/parseurl": "^1.3.3",
     "@types/statuses": "^2.0.5",
     "@types/supertest": "^6.0.2",
     "@types/type-is": "^1.6.6",
     "@types/vary": "^1.1.3",
-    "egg-bin": "^6.4.0",
     "eslint": "^8.41.0",
     "eslint-config-egg": "14",
-    "mm": "^3.3.0",
+    "mm": "^4.0.1",
     "supertest": "^3.1.0",
     "tsd": "^0.31.0",
     "tshy": "3",

src/application.ts

@@ -11,7 +11,7 @@ import onFinished from 'on-finished';
 import statuses from 'statuses';
 import compose from 'koa-compose';
 import { HttpError } from 'http-errors';
-import { Context, type ContextDelegation } from './context.js';
+import { Context } from './context.js';
 import { Request } from './request.js';
 import { Response } from './response.js';
 import type { CustomError, AnyProto } from './types.js';
@@ -21,13 +21,13 @@ const debug = debuglog('@eggjs/koa/application');
 export type ProtoImplClass<T = object> = new(...args: any[]) => T;
 export type Next = () => Promise<void>;
 type _MiddlewareFunc<T> = (ctx: T, next: Next) => Promise<void> | void;
-export type MiddlewareFunc<T = ContextDelegation> = _MiddlewareFunc<T> & { _name?: string };
+export type MiddlewareFunc<T extends Context = Context> = _MiddlewareFunc<T> & { _name?: string };
 
 /**
  * Expose `Application` class.
  * Inherits from `Emitter.prototype`.
  */
-export class Application extends Emitter {
+export class Application<T extends Context = Context> extends Emitter {
   [key: symbol]: unknown;
   /**
    * Make HttpError available to consumers of the library so that consumers don't
@@ -41,14 +41,14 @@ export class Application extends Emitter {
   proxyIpHeader: string;
   maxIpsCount: number;
   protected _keys?: string[];
-  middleware: MiddlewareFunc[];
-  ctxStorage: AsyncLocalStorage<ContextDelegation>;
+  middleware: MiddlewareFunc<T>[];
+  ctxStorage: AsyncLocalStorage<T>;
   silent: boolean;
-  ContextClass: ProtoImplClass<ContextDelegation>;
+  ContextClass: ProtoImplClass<T>;
   context: AnyProto;
-  RequestClass: ProtoImplClass<Request>;
+  RequestClass: ProtoImplClass<Request<T>>;
   request: AnyProto;
-  ResponseClass: ProtoImplClass<Response>;
+  ResponseClass: ProtoImplClass<Response<T>>;
   response: AnyProto;
 
   /**
@@ -84,11 +84,11 @@ export class Application extends Emitter {
     this.middleware = [];
     this.ctxStorage = getAsyncLocalStorage();
     this.silent = false;
-    this.ContextClass = class ApplicationContext extends Context {} as any;
+    this.ContextClass = class ApplicationContext extends Context {} as ProtoImplClass<T>;
     this.context = this.ContextClass.prototype;
-    this.RequestClass = class ApplicationRequest extends Request {};
+    this.RequestClass = class ApplicationRequest extends Request {} as ProtoImplClass<Request<T>>;
     this.request = this.RequestClass.prototype;
-    this.ResponseClass = class ApplicationResponse extends Response {};
+    this.ResponseClass = class ApplicationResponse extends Response {} as ProtoImplClass<Response<T>>;
     this.response = this.ResponseClass.prototype;
   }
 
@@ -151,7 +151,7 @@ export class Application extends Emitter {
   /**
    * Use the given middleware `fn`.
    */
-  use(fn: MiddlewareFunc) {
+  use(fn: MiddlewareFunc<T>) {
     if (typeof fn !== 'function') throw new TypeError('middleware must be a function!');
     const name = fn._name || fn.name || '-';
     if (isGeneratorFunction(fn)) {
@@ -196,7 +196,7 @@ export class Application extends Emitter {
    * Handle request in callback.
    * @private
    */
-  protected async handleRequest(ctx: ContextDelegation, fnMiddleware: (ctx: ContextDelegation) => Promise<void>) {
+  protected async handleRequest(ctx: T, fnMiddleware: (ctx: T) => Promise<void>) {
     this.emit('request', ctx);
     const res = ctx.res;
     res.statusCode = 404;
@@ -219,7 +219,7 @@ export class Application extends Emitter {
    * Initialize a new context.
    * @private
    */
-  protected createContext(req: IncomingMessage, res: ServerResponse) {
+  createContext(req: IncomingMessage, res: ServerResponse) {
     const context = new this.ContextClass(this, req, res);
     return context;
   }
@@ -246,7 +246,7 @@ export class Application extends Emitter {
   /**
    * Response helper.
    */
-  protected _respond(ctx: ContextDelegation) {
+  protected _respond(ctx: T) {
     // allow bypassing koa
     if (ctx.respond === false) return;
 
@@ -303,5 +303,3 @@ export class Application extends Emitter {
     res.end(body);
   }
 }
-
-export default Application;