From e6102efb47c299406c73396454a705c6df54658e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Simon=20Z=C3=BCnd?= <szuend@chromium.org>
Date: Thu, 8 Jan 2026 10:11:07 +0100
Subject: [PATCH] chore: implement stack trace formatting for console messages

---
 src/formatters/consoleFormatter.ts            | 41 ++++++++++++++++++
 src/third_party/devtools.ts                   |  1 +
 .../consoleFormatter.test.js.snapshot         | 10 +++++
 tests/formatters/consoleFormatter.test.ts     | 43 +++++++++++++++++++
 4 files changed, 95 insertions(+)

diff --git a/src/formatters/consoleFormatter.ts b/src/formatters/consoleFormatter.ts
index 6111e3370..06071c197 100644
--- a/src/formatters/consoleFormatter.ts
+++ b/src/formatters/consoleFormatter.ts
@@ -15,6 +15,7 @@ export interface ConsoleMessageData {
   count?: number;
   description?: string;
   args?: string[];
+  stackTrace?: DevTools.StackTrace.StackTrace.StackTrace;
 }
 
 // The short format for a console message, based on a previous format.
@@ -46,6 +47,7 @@ export function formatConsoleEventVerbose(
     `ID: ${msg.consoleMessageStableId}`,
     `Message: ${msg.type}> ${aggregatedIssue ? formatIssue(aggregatedIssue, msg.description, context) : msg.message}`,
     aggregatedIssue ? undefined : formatArgs(msg),
+    formatStackTrace(msg.stackTrace),
   ].filter(line => !!line);
   return result.join('\n');
 }
@@ -163,3 +165,42 @@ export function formatIssue(
   if (result.length === 0) return 'No affected resources found';
   return result.join('\n');
 }
+
+function formatStackTrace(
+  stackTrace: DevTools.StackTrace.StackTrace.StackTrace | undefined,
+): string {
+  if (!stackTrace) {
+    return '';
+  }
+
+  return [
+    '### Stack trace',
+    formatFragment(stackTrace.syncFragment),
+    ...stackTrace.asyncFragments.map(formatAsyncFragment),
+  ].join('\n');
+}
+
+function formatFragment(
+  fragment: DevTools.StackTrace.StackTrace.Fragment,
+): string {
+  return fragment.frames.map(formatFrame).join('\n');
+}
+
+function formatAsyncFragment(
+  fragment: DevTools.StackTrace.StackTrace.AsyncFragment,
+): string {
+  const separatorLineLength = 40;
+  const prefix = `--- ${fragment.description || 'async'} `;
+  const separator = prefix + '-'.repeat(separatorLineLength - prefix.length);
+  return separator + '\n' + formatFragment(fragment);
+}
+
+function formatFrame(frame: DevTools.StackTrace.StackTrace.Frame): string {
+  let result = `at ${frame.name ?? '<anonymous>'}`;
+  if (frame.uiSourceCode) {
+    result += ` (${frame.uiSourceCode.displayName()}:${frame.line}:${frame.column})`;
+  } else if (frame.url) {
+    result += ` (${frame.url}:${frame.line}:${frame.column})`;
+  }
+  return result;
+}
diff --git a/src/third_party/devtools.ts b/src/third_party/devtools.ts
index 5e06db4ee..d4838b178 100644
--- a/src/third_party/devtools.ts
+++ b/src/third_party/devtools.ts
@@ -7,6 +7,7 @@
 export type {
   IssuesManagerEventTypes,
   CDPConnection,
+  StackTrace,
 } from '../../node_modules/chrome-devtools-frontend/mcp/mcp.js';
 export {
   AgentFocus,
diff --git a/tests/formatters/consoleFormatter.test.js.snapshot b/tests/formatters/consoleFormatter.test.js.snapshot
index d6803572e..411b28e53 100644
--- a/tests/formatters/consoleFormatter.test.js.snapshot
+++ b/tests/formatters/consoleFormatter.test.js.snapshot
@@ -10,6 +10,16 @@ exports[`consoleFormatter > formatConsoleEventShort > formats a console.log mess
 msgid=2 [log] Processing file: (1 args)
 `;
 
+exports[`consoleFormatter > formatConsoleEventVerbose > formats a console message with a stack trace 1`] = `
+ID: 5
+Message: log> Hello stack trace!
+### Stack trace
+at foo (foo.ts:10:2)
+at bar (foo.ts:20:2)
+--- setTimeout -------------------------
+at schedule (util.ts:5:2)
+`;
+
 exports[`consoleFormatter > formatConsoleEventVerbose > formats a console.error message 1`] = `
 ID: 4
 Message: error> Something went wrong
diff --git a/tests/formatters/consoleFormatter.test.ts b/tests/formatters/consoleFormatter.test.ts
index 8734a91fe..4c7e69b71 100644
--- a/tests/formatters/consoleFormatter.test.ts
+++ b/tests/formatters/consoleFormatter.test.ts
@@ -11,6 +11,7 @@ import {
   formatConsoleEventShort,
   formatConsoleEventVerbose,
 } from '../../src/formatters/consoleFormatter.js';
+import type {DevTools} from '../../src/third_party/index.js';
 import {getMockAggregatedIssue} from '../utils.js';
 
 describe('consoleFormatter', () => {
@@ -92,6 +93,48 @@ describe('consoleFormatter', () => {
       const result = formatConsoleEventVerbose(message);
       t.assert.snapshot?.(result);
     });
+
+    it('formats a console message with a stack trace', t => {
+      const message: ConsoleMessageData = {
+        consoleMessageStableId: 5,
+        type: 'log',
+        message: 'Hello stack trace!',
+        args: [],
+        stackTrace: {
+          syncFragment: {
+            frames: [
+              {
+                line: 10,
+                column: 2,
+                url: 'foo.ts',
+                name: 'foo',
+              },
+              {
+                line: 20,
+                column: 2,
+                url: 'foo.ts',
+                name: 'bar',
+              },
+            ],
+          },
+          asyncFragments: [
+            {
+              description: 'setTimeout',
+              frames: [
+                {
+                  line: 5,
+                  column: 2,
+                  url: 'util.ts',
+                  name: 'schedule',
+                },
+              ],
+            },
+          ],
+        } as unknown as DevTools.StackTrace.StackTrace.StackTrace,
+      };
+      const result = formatConsoleEventVerbose(message);
+      t.assert.snapshot?.(result);
+    });
   });
 
   it('formats a console.log message with issue type', t => {