fix(jest-console): buffer console output in CustomConsole for reporters

CustomConsole.getBuffer() returned undefined, causing TestResult.console
to be empty when verbose mode was active. Reporters relying on
TestResult.console (e.g. custom reporters) received no console data.

Added buffer tracking to CustomConsole so it both prints live to stdout
(preserving verbose UX) and populates the buffer for reporters.

Closes #6441

Author: ahnpnl

CHANGELOG.md

@@ -1,5 +1,9 @@
 ## main
 
+### Fixes
+
+- `[jest-console]` `CustomConsole` now buffers console output so `TestResult.console` is populated for reporters when `verbose` is enabled ([#16155](https://github.com/jestjs/jest/pull/16155))
+
 ## 30.4.2
 
 ### Fixes

packages/jest-console/src/CustomConsole.ts

@@ -15,15 +15,22 @@ import {
   inspect,
 } from 'node:util';
 import chalk from 'chalk';
-import {clearLine, formatTime} from 'jest-util';
-import type {LogCounters, LogMessage, LogTimers, LogType} from './types';
+import {ErrorWithStack, clearLine, formatTime, invariant} from 'jest-util';
+import type {
+  ConsoleBuffer,
+  LogCounters,
+  LogMessage,
+  LogTimers,
+  LogType,
+} from './types';
 
 type Formatter = (type: LogType, message: LogMessage) => string;
 
 export default class CustomConsole extends Console {
   private readonly _stdout: WriteStream;
   private readonly _stderr: WriteStream;
   private readonly _formatBuffer: Formatter;
+  private readonly _buffer: ConsoleBuffer = [];
   private _counters: LogCounters = {};
   private _timers: LogTimers = {};
   private _groupDepth = 0;
@@ -46,15 +53,31 @@ export default class CustomConsole extends Console {
     super.log(
       this._formatBuffer(type, '  '.repeat(this._groupDepth) + message),
     );
+    this._addToBuffer(type, message);
   }
 
   private _logError(type: LogType, message: string) {
     clearLine(this._stderr);
     super.error(
       this._formatBuffer(type, '  '.repeat(this._groupDepth) + message),
     );
+    this._addToBuffer(type, message);
   }
 
+  private readonly _addToBuffer = (type: LogType, message: string) => {
+    const rawStack = new ErrorWithStack(undefined, this._addToBuffer).stack;
+
+    invariant(rawStack != null, 'always have a stack trace');
+
+    const origin = rawStack.split('\n').slice(3).filter(Boolean).join('\n');
+
+    this._buffer.push({
+      message: '  '.repeat(this._groupDepth) + message,
+      origin,
+      type,
+    });
+  };
+
   override assert(value: unknown, message?: string | Error): asserts value {
     try {
       assert.ok(value, message);
@@ -159,7 +182,7 @@ export default class CustomConsole extends Console {
     this._logError('warn', format(firstArg, ...args));
   }
 
-  getBuffer(): undefined {
-    return undefined;
+  getBuffer(): ConsoleBuffer | undefined {
+    return this._buffer.length > 0 ? this._buffer : undefined;
   }
 }

packages/jest-console/src/__tests__/CustomConsole.test.ts

@@ -241,4 +241,62 @@ describe('CustomConsole', () => {
       expect(_console.Console).toBeDefined();
     });
   });
+
+  describe('getBuffer', () => {
+    test('should return undefined when no messages have been logged', () => {
+      expect(_console.getBuffer()).toBeUndefined();
+    });
+
+    test('should return buffer with log entries after logging', () => {
+      _console.log('Hello world!');
+
+      const buffer = _console.getBuffer();
+      expect(buffer).toBeDefined();
+      expect(buffer).toHaveLength(1);
+      expect(buffer![0].message).toBe('Hello world!');
+      expect(buffer![0].type).toBe('log');
+      expect(buffer![0].origin).toBeDefined();
+    });
+
+    test('should buffer error messages', () => {
+      _console.error('Some error');
+
+      const buffer = _console.getBuffer();
+      expect(buffer).toBeDefined();
+      expect(buffer).toHaveLength(1);
+      expect(buffer![0].message).toBe('Some error');
+      expect(buffer![0].type).toBe('error');
+    });
+
+    test('should buffer warn messages', () => {
+      _console.warn('Some warning');
+
+      const buffer = _console.getBuffer();
+      expect(buffer).toBeDefined();
+      expect(buffer).toHaveLength(1);
+      expect(buffer![0].message).toBe('Some warning');
+      expect(buffer![0].type).toBe('warn');
+    });
+
+    test('should accumulate multiple log entries', () => {
+      _console.log('first');
+      _console.error('second');
+      _console.warn('third');
+
+      const buffer = _console.getBuffer();
+      expect(buffer).toHaveLength(3);
+      expect(buffer![0].type).toBe('log');
+      expect(buffer![1].type).toBe('error');
+      expect(buffer![2].type).toBe('warn');
+    });
+
+    test('should still print to stdout/stderr while buffering', () => {
+      _console.log('to stdout');
+      _console.error('to stderr');
+
+      expect(_stdout).toBe('to stdout\n');
+      expect(_stderr).toBe('to stderr\n');
+      expect(_console.getBuffer()).toHaveLength(2);
+    });
+  });
 });

packages/jest-reporters/src/DefaultReporter.ts

@@ -227,7 +227,7 @@ export default class DefaultReporter extends BaseReporter {
     }
 
     this.log(getResultHeader(result, this._globalConfig, config));
-    if (result.console) {
+    if (result.console && !this._globalConfig.verbose) {
       this.log(
         `  ${TITLE_BULLET}Console\n\n${getConsoleOutput(result.console, config, this._globalConfig)}`,
       );