happy-dom 20.11.2: VirtualConsolePrinter buffers console logs, destructively drains on read/readAsString calls, filters by log level, formats group indentation and collapsed group suppression, dispatches lifecycle events, and is exposed on Window via happyDOM.virtualConsolePrinter.

# happy-dom VirtualConsolePrinter

## Discovery
The solution search returned `NO_SAFE_MATCH` for `happy-dom.VirtualConsolePrinter` on `happy-dom@20.11.2`.

## Pinned Release
- `happy-dom`: `20.11.2`

## Observed Behavior
`VirtualConsolePrinter` manages captured virtual console logs in Happy-DOM:

1. **Destructive Buffer Reads**: Both `.read()` and `.readAsString()` empty the internal buffer (`#logEntries = []`) when called. A developer expecting `.read()` or `.readAsString()` to be non-destructive inspection calls will find subsequent reads returning empty arrays `[]` or empty strings `""`.
2. **Log Level Filtering Drains Buffer**: `.readAsString(minLogLevel)` filters output to include only entries whose level is greater than or equal to `minLogLevel` (using `VirtualConsoleLogLevelEnum`), but because it delegates to `.read()`, all buffered entries are drained, discarding lower-severity entries from the buffer as well.
3. **Group Formatting & Collapsed Suppression**: Log entries within a `console.group()` are indented with two spaces per level and prefixed with `▼ `. Entries within a `console.groupCollapsed()` are prefixed with `▶ ` for the group header, but any messages logged inside the collapsed group return empty strings and are suppressed from `.readAsString()`.
4. **Lifecycle & Events**: Dispatches synchronous DOM `Event` objects (`'print'` on `print()`, `'clear'` on `clear()`). Unsupported event names throw an error. Calling `.close()` sets `.closed` to `true`, clears all listeners and buffered entries, and causes subsequent calls to `.print()`, `.clear()`, and listener additions to be ignored.
5. **Window Integration**: Each `BrowserPage` creates a default `VirtualConsolePrinter`, accessible on detached `Window` instances via `window.happyDOM.virtualConsolePrinter`.

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import assert from 'node:assert/strict';
import {
  VirtualConsolePrinter,
  VirtualConsole,
  VirtualConsoleLogLevelEnum,
  Window
} from 'happy-dom';

// 1. Destructive read() and readAsString() buffer draining
{
  const printer = new VirtualConsolePrinter();
  const vc = new VirtualConsole(printer);

  vc.log('first message');
  vc.log('second message');

  // Initial read returns all buffered log entries
  const entries = printer.read();
  assert.strictEqual(entries.length, 2);
  assert.strictEqual(entries[0].message[0], 'first message');
  assert.strictEqual(entries[1].message[0], 'second message');

  // Immediately reading again returns an empty array because read() drained the buffer
  const secondRead = printer.read();
  assert.deepStrictEqual(secondRead, []);

  // readAsString() also drains the buffer
  vc.log('third message');
  const strOutput = printer.readAsString();
  assert.strictEqual(strOutput, 'third message\n');

  const secondStrOutput = printer.readAsString();
  assert.strictEqual(secondStrOutput, '');
}

// 2. Log level filtering in readAsString() drains all entries including skipped ones
{
  const printer = new VirtualConsolePrinter();
  const vc = new VirtualConsole(printer);

  vc.log('debug/log level text'); // level 0 (log)
  vc.info('info level text');      // level 1 (info)
  vc.warn('warn level text');      // level 2 (warn)
  vc.error('error level text');    // level 3 (error)

  // Request only warn and error (level >= 2)
  const warnAndAbove = printer.readAsString(VirtualConsoleLogLevelEnum.warn);
  assert.strictEqual(warnAndAbove, 'warn level text\nerror level text\n');

  // Buffer is completely drained — even the log/info messages were consumed and are gone
  assert.deepStrictEqual(printer.read(), []);
}

// 3. Group formatting, tabbing, and collapsed group suppression
{
  const printer = new VirtualConsolePrinter();
  const vc = new VirtualConsole(printer);

  // Expanded group
  vc.group('Active Group');
  vc.log('nested item');
  vc.groupEnd();
  vc.log('root item');

  const expandedOutput = printer.readAsString();
  assert.strictEqual(expandedOutput, '▼ Active Group\n  nested item\nroot item\n');

  // Collapsed group suppresses nested log output in readAsString
  vc.groupCollapsed('Hidden Group');
  vc.log('this message will be suppressed in readAsString');
  vc.groupEnd();
  vc.log('visible after groupEnd');

  const collapsedOutput = printer.readAsString();
  assert.strictEqual(collapsedOutput, '▶ Hidden Group\nvisible after groupEnd\n');
}

// 4. Event listeners for 'print' and 'clear'
{
  const printer = new VirtualConsolePrinter();
  const vc = new VirtualConsole(printer);

  const printEvents = [];
  const clearEvents = [];

  const onPrint = (event) => printEvents.push(event.type);
  const onClear = (event) => clearEvents.push(event.type);

  printer.addEventListener('print', onPrint);
  printer.addEventListener('clear', onClear);

  vc.log('event trigger 1');
  vc.warn('event trigger 2');
  assert.strictEqual(printEvents.length, 2);
  assert.strictEqual(printEvents[0], 'print');
  assert.strictEqual(printEvents[1], 'print');

  vc.clear();
  assert.strictEqual(clearEvents.length, 1);
  assert.strictEqual(clearEvents[0], 'clear');

  // Removing listener
  printer.removeEventListener('print', onPrint);
  vc.log('event trigger 3');
  assert.strictEqual(printEvents.length, 2);

  // Unsupported event type throws
  assert.throws(() => {
    printer.addEventListener('invalidEvent', () => {});
  }, /Event type "invalidEvent" is not supported\./);
}

// 5. Lifecycle and close() behavior
{
  const printer = new VirtualConsolePrinter();
  const vc = new VirtualConsole(printer);

  let eventFired = false;
  printer.addEventListener('print', () => { eventFired = true; });

  assert.strictEqual(printer.closed, false);
  vc.log('pre-close log');

  printer.close();
  assert.strictEqual(printer.closed, true);

  // Buffer is emptied on close
  assert.deepStrictEqual(printer.read(), []);

  // Operations on closed printer are no-ops
  eventFired = false;
  vc.log('post-close log');
  assert.strictEqual(eventFired, false);
  assert.deepStrictEqual(printer.read(), []);
  assert.strictEqual(printer.readAsString(), '');
}

// 6. Access via Window and happyDOM.virtualConsolePrinter
{
  const window = new Window();
  assert.ok(window.happyDOM.virtualConsolePrinter instanceof VirtualConsolePrinter);

  window.console.log('window log message');
  const windowOutput = window.happyDOM.virtualConsolePrinter.readAsString();
  assert.strictEqual(windowOutput, 'window log message\n');

  window.happyDOM.close();
}