fix(server): unique context objects per request (#1246)

.changeset/violet-dancers-wash.md

@@ -0,0 +1,9 @@
+---
+"@whatwg-node/server": patch
+---
+
+Ensure unique context objects are sent per each request.
+
+For example in CloudFlare Workers,
+`fetch` receives `env` and `ctx`, and `env` is shared across requests. That causes the server receives the same context object for each request.
+Now the server creates a new context object for each request, even if the first argument is the same. Before, it always takes the first argument as the context object, then merges the following arguments into it.

benchmarks/server/tsconfig.json

@@ -4,7 +4,8 @@
     "baseUrl": "./",
     "outDir": "dist",
     "module": "Node16",
-    "moduleResolution": "node16"
+    "moduleResolution": "node16",
+    "skipLibCheck": true
   },
   "include": ["server.ts"],
   "exclude": []

packages/server/src/createServerAdapter.ts

@@ -313,7 +313,7 @@ function createServerAdapter<
     let waitUntilPromises: Promise<void>[] | undefined;
     const serverContext =
       filteredCtxParts.length > 1
-        ? completeAssign(...filteredCtxParts)
+        ? completeAssign({}, ...filteredCtxParts)
         : isolateObject(
             filteredCtxParts[0],
             filteredCtxParts[0] == null || filteredCtxParts[0].waitUntil == null

packages/server/test/adapter.fetch.spec.ts

@@ -227,4 +227,25 @@ describe('adapter.fetch', () => {
     controller.abort();
     await expect(promise).rejects.toThrow('This operation was aborted');
   });
+
+  it('should provide a unique context for each request', async () => {
+    const requestHandler = jest.fn((_req: Request, _ctx: any) =>
+      Response.json({
+        hello: 'world',
+      }),
+    );
+    const sharedCtxPart1 = { foo: 'bar' };
+    const sharedCtxPart2 = { bar: 'baz' };
+    const adapter = createServerAdapter(requestHandler);
+    const request1 = new Request('http://localhost:8080/');
+    const response1 = await adapter.fetch(request1, sharedCtxPart1, sharedCtxPart2);
+    const response1Body = await response1.json();
+    expect(response1Body).toEqual({ hello: 'world' });
+    const request2 = new Request('http://localhost:8080/');
+    const response2 = await adapter.fetch(request2, sharedCtxPart1, sharedCtxPart2);
+    const response2Body = await response2.json();
+    expect(response2Body).toEqual({ hello: 'world' });
+    expect(requestHandler).toHaveBeenCalledTimes(2);
+    expect(requestHandler.mock.calls[0][1]).not.toBe(requestHandler.mock.calls[1][1]);
+  });
 });

tsconfig.json

@@ -31,6 +31,6 @@
       "fetchache": ["packages/fetchache/src/index.ts"]
     }
   },
-  "include": ["packages", "examples", "uwsUtils.d.ts"],
+  "include": ["packages", "examples", "uwsUtils.d.ts", "scheduler-tracing.d.ts"],
   "exclude": ["**/node_modules", "**/test-files", "**/dist", "**/e2e", "**/benchmark"]
 }