fix(network): improve error message when response.body() is called after navigation

packages/playwright-core/src/server/network.ts

@@ -16,6 +16,8 @@
 
 import { ManualPromise } from '@isomorphic/manualPromise';
 import { assert } from '@isomorphic/assert';
+import { rewriteErrorMessage } from '@isomorphic/stackTrace';
+import { isProtocolError } from './protocolError';
 import { BrowserContext } from './browserContext';
 import { APIRequestContext } from './fetch';
 import { SdkObject } from './instrumentation';
@@ -651,7 +653,13 @@ export class Response extends SdkObject {
           const { body, isBase64 } = this._request._responseBodyOverride;
           return Buffer.from(body, isBase64 ? 'base64' : 'utf-8');
         }
-        return this._getResponseBodyCallback();
+        try {
+          return await this._getResponseBodyCallback();
+        } catch (e) {
+          if (isProtocolError(e) && e.type === 'error')
+            rewriteErrorMessage(e, e.message + '\nResponse body is not available for a response that was navigated away from. Read response.body() before triggering any navigation.');
+          throw e;
+        }
       });
     }
     return this._contentPromise;

tests/page/page-network-response.spec.ts

@@ -450,3 +450,17 @@ it('Response.formData() should parse multipart/form-data in page context', async
   expect(result.filename).toBe('test.txt');
   expect(result.fileContent).toBe('hello');
 });
+
+it('should give a readable error when response.body() races with navigation', async ({ page, server, browserName }) => {
+  it.skip(browserName === 'firefox', 'Firefox has a separate eviction error path');
+  it.info().annotations.push({ type: 'issue', description: 'https://github.com/microsoft/playwright/issues/41512' });
+  const [response] = await Promise.all([
+    page.waitForResponse(server.EMPTY_PAGE),
+    page.goto(server.EMPTY_PAGE),
+  ]);
+  // Navigate away — the browser frees the network resource from the first page load
+  await page.goto(server.PREFIX + '/title.html');
+  const error = await response.body().catch(e => e);
+  expect(error).toBeInstanceOf(Error);
+  expect(error.message).toContain('navigated away');
+});