Support integration with Koa

README.md

@@ -190,6 +190,21 @@ export default {
 };
 ```
 
+##### With [`Koa`](https://koajs.com/)
+
+```js
+import Koa from 'koa'; // yarn add koa
+import mount from 'koa-mount'; // yarn add koa-mount
+import { createHandler } from 'graphql-http/lib/use/koa';
+import { schema } from './previous-step';
+
+const app = new Koa();
+app.use(mount('/graphql', createHandler({ schema })));
+
+app.listen({ port: 4000 });
+console.log('Listening to port 4000');
+```
+
 #### Use the client
 
 ```js

package.json

@@ -55,6 +55,11 @@
       "require": "./lib/use/fastify.js",
       "import": "./lib/use/fastify.mjs"
     },
+    "./lib/use/koa": {
+      "types": "./lib/use/koa.d.ts",
+      "require": "./lib/use/koa.js",
+      "import": "./lib/use/koa.mjs"
+    },
     "./package.json": "./package.json"
   },
   "types": "lib/index.d.ts",
@@ -105,6 +110,8 @@
     "@types/express": "^4.17.15",
     "@types/glob": "^8.0.0",
     "@types/jest": "^29.2.4",
+    "@types/koa": "^2.13.5",
+    "@types/koa-mount": "^4.0.2",
     "@typescript-eslint/eslint-plugin": "^5.47.0",
     "@typescript-eslint/parser": "^5.47.0",
     "@whatwg-node/fetch": "^0.5.3",
@@ -116,6 +123,8 @@
     "graphql": "^16.6.0",
     "jest": "^29.3.1",
     "jest-jasmine2": "^29.3.1",
+    "koa": "^2.14.1",
+    "koa-mount": "^4.0.0",
     "node-fetch": "^3.3.0",
     "prettier": "^2.8.1",
     "rollup": "^3.8.1",

src/__tests__/use.ts

@@ -2,6 +2,8 @@ import { fetch } from '@whatwg-node/fetch';
 import http from 'http';
 import express from 'express';
 import fastify from 'fastify';
+import Koa from 'koa';
+import mount from 'koa-mount';
 import { createServerAdapter } from '@whatwg-node/server';
 import { startDisposableServer } from './utils/tserver';
 import { serverAudits } from '../audits';
@@ -11,6 +13,7 @@ import { createHandler as createNodeHandler } from '../use/node';
 import { createHandler as createExpressHandler } from '../use/express';
 import { createHandler as createFastifyHandler } from '../use/fastify';
 import { createHandler as createFetchHandler } from '../use/fetch';
+import { createHandler as createKoaHandler } from '../use/koa';
 
 describe('node', () => {
   const [url, dispose] = startDisposableServer(
@@ -90,3 +93,20 @@ describe('fetch', () => {
     });
   }
 });
+
+describe('koa', () => {
+  const app = new Koa();
+  app.use(mount('/', createKoaHandler({ schema })));
+
+  const [url, dispose] = startDisposableServer(app.listen(0));
+  afterAll(dispose);
+
+  for (const audit of serverAudits({ url, fetchFn: fetch })) {
+    it(audit.name, async () => {
+      const result = await audit.fn();
+      if (result.status !== 'ok') {
+        throw result.reason;
+      }
+    });
+  }
+});

src/use/koa.ts

@@ -0,0 +1,85 @@
+import type { Middleware } from 'koa';
+import type { IncomingMessage } from 'http';
+import {
+  createHandler as createRawHandler,
+  HandlerOptions,
+  OperationContext,
+} from '../handler';
+
+/**
+ * Create a GraphQL over HTTP Protocol compliant request handler for
+ * the Koa framework.
+ *
+ * ```js
+ * import Koa from 'koa'; // yarn add koa
+ * import mount from 'koa-mount'; // yarn add koa-mount
+ * import { createHandler } from 'graphql-http/lib/use/koa';
+ * import { schema } from './my-graphql-schema';
+ *
+ * const app = new Koa();
+ * app.use(mount('/', createHandler({ schema })));
+ *
+ * app.listen({ port: 4000 });
+ * console.log('Listening to port 4000');
+ * ```
+ *
+ * @category Server/koa
+ */
+export function createHandler<Context extends OperationContext = undefined>(
+  options: HandlerOptions<IncomingMessage, undefined, Context>,
+): Middleware {
+  const isProd = process.env.NODE_ENV === 'production';
+  const handle = createRawHandler(options);
+  return async function requestListener(ctx) {
+    try {
+      const [body, init] = await handle({
+        url: ctx.url,
+        method: ctx.method,
+        headers: ctx.headers,
+        body: () => {
+          if (ctx.body) {
+            // in case koa has a body parser
+            return ctx.body;
+          }
+          return new Promise<string>((resolve) => {
+            let body = '';
+            ctx.req.on('data', (chunk) => (body += chunk));
+            ctx.req.on('end', () => resolve(body));
+          });
+        },
+        raw: ctx.req,
+        context: undefined,
+      });
+      ctx.body = body;
+      ctx.response.status = init.status;
+      ctx.response.message = init.statusText;
+      if (init.headers) {
+        for (const [name, value] of Object.entries(init.headers)) {
+          ctx.response.set(name, value);
+        }
+      }
+    } catch (err) {
+      // The handler shouldnt throw errors.
+      // If you wish to handle them differently, consider implementing your own request handler.
+      console.error(
+        'Internal error occurred during request handling. ' +
+          'Please check your implementation.',
+        err,
+      );
+      ctx.response.status = 500;
+      if (!isProd) {
+        ctx.response.set('content-type', 'application/json; charset=utf-8');
+        ctx.body = {
+          errors: [
+            err instanceof Error
+              ? {
+                  message: err.message,
+                  stack: err.stack,
+                }
+              : err,
+          ],
+        };
+      }
+    }
+  };
+}