feat: add types

.github/workflows/ci.yml

@@ -31,6 +31,9 @@ jobs:
       - name: Lint code
         run: npm run lint
 
+      - name: Check types
+        run: npm run test-types
+
   test:
     name: Test - Node.js ${{ matrix.node-version }}
     runs-on: ubuntu-latest

index.d.ts

@@ -0,0 +1,20 @@
+/// <reference types="node" />
+
+import { IncomingMessage, ServerResponse } from "node:http";
+
+declare function finalhandler(
+  req: IncomingMessage,
+  res: ServerResponse,
+  options?: finalhandler.Options
+): (err?: any) => void;
+
+declare namespace finalhandler {
+  interface Options {
+    env?: string | undefined;
+    onerror?:
+      | ((err: any, req: IncomingMessage, res: ServerResponse) => void)
+      | undefined;
+  }
+}
+
+export = finalhandler;

package.json

@@ -5,6 +5,9 @@
   "author": "Douglas Christopher Wilson <[email protected]>",
   "license": "MIT",
   "repository": "pillarjs/finalhandler",
+  "type": "commonjs",
+  "main": "index.js",
+  "types": "index.d.ts",
   "dependencies": {
     "debug": "^4.4.0",
     "encodeurl": "^2.0.0",
@@ -14,21 +17,27 @@
     "statuses": "^2.0.1"
   },
   "devDependencies": {
+    "@arethetypeswrong/cli": "^0.17.4",
+    "@tsconfig/node18": "^18.2.4",
+    "@types/node": "^22.13.10",
     "eslint": "7.32.0",
     "eslint-config-standard": "14.1.1",
     "eslint-plugin-import": "2.26.0",
     "eslint-plugin-markdown": "2.2.1",
     "eslint-plugin-node": "11.1.0",
     "eslint-plugin-promise": "5.2.0",
     "eslint-plugin-standard": "4.1.0",
+    "expect-type": "^1.2.0",
     "mocha": "^11.0.1",
     "nyc": "^17.1.0",
-    "supertest": "^7.0.0"
+    "supertest": "^7.0.0",
+    "typescript": "^5.8.2"
   },
   "files": [
     "LICENSE",
     "HISTORY.md",
-    "index.js"
+    "index.js",
+    "index.d.ts"
   ],
   "engines": {
     "node": ">= 0.8"
@@ -38,6 +47,7 @@
     "test": "mocha --reporter spec --check-leaks test/",
     "test-ci": "nyc --reporter=lcovonly --reporter=text npm test",
     "test-cov": "nyc --reporter=html --reporter=text npm test",
-    "test-inspect": "mocha --reporter spec --inspect --inspect-brk test/"
+    "test-inspect": "mocha --reporter spec --inspect --inspect-brk test/",
+    "test-types": "tsc --noEmit && attw --pack"
   }
 }

test/types.ts

@@ -0,0 +1,46 @@
+import { IncomingMessage, ServerResponse, createServer } from "node:http";
+import { expectTypeOf } from "expect-type";
+import finalhandler, { Options } from "..";
+
+const req = {} as IncomingMessage;
+const res = {} as ServerResponse;
+
+const options: Options = {
+  env: "anEnv",
+  onerror: (err, req, res) => {
+    expectTypeOf(err).toBeAny();
+    expectTypeOf(req).toEqualTypeOf<IncomingMessage>();
+    expectTypeOf(res).toEqualTypeOf<ServerResponse>();
+  },
+};
+
+expectTypeOf(options.env).toEqualTypeOf<string | undefined>();
+
+// finalhandler without options
+{
+  const result = finalhandler(req, res);
+  expectTypeOf(result).toBeFunction();
+  expectTypeOf(result).parameters.toEqualTypeOf<[any?]>();
+  expectTypeOf(result).returns.toBeVoid();
+  expectTypeOf(result).toBeCallableWith(new Error());
+}
+
+// finalhandler with options
+{
+  const result = finalhandler(req, res, options);
+  expectTypeOf(result).toBeFunction();
+  expectTypeOf(result).parameters.toEqualTypeOf<[any?]>();
+  expectTypeOf(result).returns.toBeVoid();
+  expectTypeOf(result).toBeCallableWith(new Error());
+}
+
+// serve-static-like request handler
+declare function requestHandler(
+  request: IncomingMessage,
+  response: ServerResponse,
+  next: (err?: any) => void
+): any;
+
+createServer((req, res) => {
+  requestHandler(req, res, finalhandler(req, res));
+});

tsconfig.json

@@ -0,0 +1,4 @@
+{
+  "extends": "@tsconfig/node18/tsconfig.json",
+  "include": ["index.d.ts", "test/types.ts"]
+}