🐛 Explain cancelled browser operations

src/browser-control.js

@@ -7,12 +7,9 @@ import { nativeCapabilities, normalizeNative } from './native.js';
 import { createObserver } from './observer.js';
 
 let problem = (status, message) => Object.assign(new Error(message), { status });
+let contextFields = Object.freeze(['executionId', 'documentId', 'revision', 'width', 'height']);
 let sameContext = (left, right) =>
-  left &&
-  right &&
-  ['executionId', 'documentId', 'revision', 'width', 'height'].every(
-    (key) => left[key] === right[key],
-  );
+  left && right && contextFields.every((key) => left[key] === right[key]);
 let commands = [
   'pause',
   'continue',
@@ -207,24 +204,28 @@ export function createBrowserControl({ artifactsDir, workerId = '0', onReplaced
       throw problem(409, 'This managed browser has moved to another run.');
     return connection;
   };
-  let discard = async (record, includeCommitted = false) => {
+  let discard = async (
+    record,
+    includeCommitted = false,
+    reason = problem(409, 'Screenshot context ended.'),
+  ) => {
     if (record.status === 'accepted') return;
-    record.controller.abort(problem(409, 'Screenshot context ended.'));
+    record.controller.abort(reason);
     if (record.status !== 'committed' || includeCommitted) {
       records.delete(record.id);
       await rm(record.partial, { force: true });
       await rm(record.file, { force: true });
     }
   };
-  let invalidate = (runId, endingRun = false) => {
+  let invalidate = (runId, endingRun = false, reason) => {
     contexts.delete(runId);
     for (let request of nativeRequests.values())
       if (request.runId === runId && (endingRun || request.kind !== 'key'))
         request.controller.abort(problem(409, 'The native input context ended.'));
     for (let record of records.values()) {
       if (record.runId !== runId || record.status === 'accepted') continue;
       if (record.status === 'committed' && !endingRun) continue;
-      void track(discard(record, endingRun)).catch(() => {});
+      void track(discard(record, endingRun, reason)).catch(() => {});
     }
   };
   let active = (record) =>
@@ -468,7 +469,21 @@ export function createBrowserControl({ artifactsDir, workerId = '0', onReplaced
             assignment.id === input.context.executionId && assignment.status !== 'released' && !run.tests[assignment.index].skipReason)))
           throw problem(409, 'This execution does not own an active test assignment.');
         let previous = contexts.get(input.runId);
-        if (!sameContext(previous, input.context)) invalidate(input.runId);
+        if (!sameContext(previous, input.context)) {
+          let changes = contextFields
+            .filter((key) => previous?.[key] !== input.context?.[key])
+            .map((key) => `${key}: ${previous?.[key] ?? 'none'} → ${input.context?.[key] ?? 'none'}`);
+          let describe = (viewport) =>
+            `${viewport?.width} × ${viewport?.height} at DPR ${viewport?.pixelRatio}`;
+          let viewportChange = input.viewportChange
+            ? ` Browser viewport: ${describe(input.viewportChange.previous)} → ${describe(input.viewportChange.measured)}.`
+            : '';
+          invalidate(
+            input.runId,
+            false,
+            problem(409, `Screenshot context changed (${changes.join(', ')}).${viewportChange}`),
+          );
+        }
         if (input.context) {
           if (
             !validViewport(input.context, Number.MAX_SAFE_INTEGER) ||

src/browser-session.js

@@ -131,7 +131,11 @@ export async function createBrowserPool(plan, { size = 1, signal, onExit = () =>
         catch { /* Channel closure still rejects and removes this request below. */ }
       }
       requests.delete(id);
-      request.reject(new Error(`Browser ${method} cancelled or exceeded its deadline.`, { cause: deadline.reason }));
+      let reason = deadline.reason;
+      let message = reason?.name === 'TimeoutError'
+        ? `Browser ${method} exceeded its deadline.`
+        : `Browser ${method} cancelled: ${reason?.message ?? String(reason)}`;
+      request.reject(new Error(message.replaceAll(server.wsEndpoint(), '[private browser connection]'), { cause: reason }));
     };
     deadline.addEventListener('abort', abort, { once: true });
     try {

src/browser/shell.js

@@ -146,9 +146,11 @@ let context = (current) =>
         ...state.viewport,
       }
     : null;
-let syncContext = (current) => {
+let syncContext = (current, viewportChange) => {
   let value = context(current);
-  contextSync = contextSync.catch(() => {}).then(() => post('context', { context: value }));
+  contextSync = contextSync.catch(() => {}).then(() =>
+    post('context', { context: value, ...(viewportChange ? { viewportChange } : {}) }),
+  );
   return contextSync;
 };
 let assertCurrent = (current, documentId, revision, metrics, operation = 'screenshot') => {
@@ -418,9 +420,11 @@ window.addEventListener('message', (event) => {
   if (message.kind === 'resize' && message.executionId === resource?.id) {
     let measured = { ...appSize(), pixelRatio: appWindow.devicePixelRatio };
     if (Object.keys(measured).every((key) => measured[key] === observedViewport[key])) return;
+    let previous = observedViewport;
     observedViewport = measured;
     update({ type: 'browser.resized', viewport: appSize() });
-    if (runId) void syncContext(resource).catch((error) => console.error(error));
+    if (runId)
+      void syncContext(resource, { previous, measured }).catch((error) => console.error(error));
   }
 });
 window.addEventListener('pagehide', () => {

tests/native/pool.test.js

@@ -252,7 +252,7 @@ test('cancelling queued viewport work closes the pool before it can be reused',
   let cancel = new AbortController();
   let resizing = workers[0].resize({ width: 400, height: 300 }, cancel.signal);
   cancel.abort(new Error('Viewport request ended'));
-  await assert.rejects(resizing, /cancelled/);
+  await assert.rejects(resizing, /cancelled: Viewport request ended/);
   await assert.rejects(opening);
   await assert.rejects(workers[1].open(origin), /closed/);
   await assert.rejects(pool.createWorker('c'), /closed/);