Restore Content-Length header in inspector-proxy JSON responses

Summary:
Changelog: [General][Fixed] Re-enable listing Hermes debugger targets in chrome://inspect, broken in 0.74 RC

Fixes #43259.

Reverts D52958725 and fixes the original `Content-Length` Unicode bug using a different approach.

Reviewed By: fabriziocucci

Differential Revision: D54409847

fbshipit-source-id: ed5bb464ab67f37535947646b124814d8bbf797c

packages/dev-middleware/src/__tests__/InspectorProxyHttpApi-test.js

@@ -14,11 +14,13 @@ import type {
   JsonVersionResponse,
 } from '../inspector-proxy/types';
 
-import {fetchJson} from './FetchUtils';
+import {fetchJson, fetchLocal} from './FetchUtils';
 import {createDeviceMock} from './InspectorDeviceUtils';
 import {withAbortSignalForEachTest} from './ResourceUtils';
 import {withServerForEachTest} from './ServerUtils';
 
+import nullthrows from 'nullthrows';
+
 // Must be greater than or equal to PAGES_POLLING_INTERVAL in `InspectorProxy.js`.
 const PAGES_POLLING_DELAY = 1000;
 
@@ -309,5 +311,67 @@ describe('inspector proxy HTTP API', () => {
         }
       });
     });
+
+    test('handles Unicode data safely', async () => {
+      const device = await createDeviceMock(
+        `${serverRef.serverBaseWsUrl}/inspector/device?device=device1&name=foo&app=bar`,
+        autoCleanup.signal,
+      );
+      try {
+        device.getPages.mockImplementation(() => [
+          {
+            app: 'bar-app 📱',
+            id: 'page1 🛂',
+            title: 'bar-title 📰',
+            vm: 'bar-vm 🤖',
+          },
+        ]);
+
+        jest.advanceTimersByTime(PAGES_POLLING_DELAY);
+
+        const json = await fetchJson<JsonPagesListResponse>(
+          `${serverRef.serverBaseUrl}${endpoint}`,
+        );
+        expect(json).toEqual([
+          expect.objectContaining({
+            description: 'bar-app 📱',
+            deviceName: 'foo',
+            id: 'device1-page1 🛂',
+            title: 'bar-title 📰',
+            vm: 'bar-vm 🤖',
+          }),
+        ]);
+      } finally {
+        device.close();
+      }
+    });
+
+    test('includes a valid Content-Length header', async () => {
+      // NOTE: This test is needed because chrome://inspect's HTTP client is picky
+      // and doesn't accept responses without a Content-Length header.
+      const device = await createDeviceMock(
+        `${serverRef.serverBaseWsUrl}/inspector/device?device=device1&name=foo&app=bar`,
+        autoCleanup.signal,
+      );
+      try {
+        device.getPages.mockImplementation(() => [
+          {
+            app: 'bar-app',
+            id: 'page1',
+            title: 'bar-title',
+            vm: 'bar-vm',
+          },
+        ]);
+
+        jest.advanceTimersByTime(PAGES_POLLING_DELAY);
+
+        const response = await fetchLocal(
+          `${serverRef.serverBaseUrl}${endpoint}`,
+        );
+        expect(response.headers.get('Content-Length')).not.toBeNull();
+      } finally {
+        device.close();
+      }
+    });
   });
 });

packages/dev-middleware/src/inspector-proxy/InspectorProxy.js

@@ -167,6 +167,7 @@ export default class InspectorProxy implements InspectorProxyQueries {
     response.writeHead(200, {
       'Content-Type': 'application/json; charset=UTF-8',
       'Cache-Control': 'no-cache',
+      'Content-Length': Buffer.byteLength(data).toString(),
       Connection: 'close',
     });
     response.end(data);