fix(grid): result grids leak through a PiiMaskingController listener (#1555)

lib/features/workspace/result_grid_view.dart

@@ -159,12 +159,20 @@ class _VirtualResultGridState extends material.State<VirtualResultGrid> {
   ResultGridColumnWindow? _currentWindow;
   double _currentRowsViewportHeight = 0.0;
 
+  /// Handlers that live in `extension _Grid* on _VirtualResultGridState`. Tearing
+  /// off an extension method makes a new closure each time and two of them are
+  /// never equal, so `removeListener(_onPiiMaskingChanged)` would not find what
+  /// `addListener(_onPiiMaskingChanged)` stored (#1555). Keep one closure and
+  /// pass that to both.
+  late final void Function() _piiMaskingListener = _onPiiMaskingChanged;
+  late final void Function() _horizontalScrollListener = _onHorizontalScroll;
+
   @override
   void initState() {
     super.initState();
-    _horizontalController.addListener(_onHorizontalScroll);
+    _horizontalController.addListener(_horizontalScrollListener);
     _verticalController.addListener(_onVerticalScroll);
-    PiiMaskingController.instance.addListener(_onPiiMaskingChanged);
+    PiiMaskingController.instance.addListener(_piiMaskingListener);
     widget.stagingBuffer?.addListener(_onStagingBufferChanged);
     _lastKnownStagedRowCount = _baseRows.length;
     _updateSortedRows();
@@ -389,11 +397,11 @@ class _VirtualResultGridState extends material.State<VirtualResultGrid> {
   void dispose() {
     _hideCellTooltip();
     _selectionValuesDebounce?.cancel();
-    PiiMaskingController.instance.removeListener(_onPiiMaskingChanged);
+    PiiMaskingController.instance.removeListener(_piiMaskingListener);
     _stopAutoScroll();
     _rowWidgets.clear();
     widget.stagingBuffer?.removeListener(_onStagingBufferChanged);
-    _horizontalController.removeListener(_onHorizontalScroll);
+    _horizontalController.removeListener(_horizontalScrollListener);
     _horizontalController.dispose();
     _verticalController.removeListener(_onVerticalScroll);
     _verticalController.dispose();

test/features/workspace/result_grid_listener_leak_test.dart

@@ -0,0 +1,44 @@
+import 'package:flutter/material.dart' as material;
+import 'package:flutter_test/flutter_test.dart';
+import 'package:querya_desktop/core/security/pii_masking_controller.dart';
+import 'package:querya_desktop/features/workspace/result_grid_view.dart';
+
+import '../../support/querya_theme_test_shell.dart';
+
+material.Widget _shell({required material.Widget child}) {
+  return queryaThemeTestShell(child: material.Scaffold(body: child));
+}
+
+void main() {
+  group('VirtualResultGrid listeners (#1555)', () {
+    testWidgets('disposing a grid removes its listener from PiiMaskingController',
+        (tester) async {
+      // ignore: invalid_use_of_protected_member
+      final before = PiiMaskingController.instance.hasListeners;
+
+      await tester.pumpWidget(
+        _shell(
+          child: const material.SizedBox(
+            width: 800,
+            height: 400,
+            child: VirtualResultGrid(
+              columns: ['id', 'name'],
+              rows: [
+                ['1', 'Alice'],
+              ],
+            ),
+          ),
+        ),
+      );
+      await tester.pumpAndSettle();
+      // ignore: invalid_use_of_protected_member
+      expect(PiiMaskingController.instance.hasListeners, isTrue);
+
+      await tester.pumpWidget(_shell(child: const material.SizedBox()));
+      await tester.pumpAndSettle();
+
+      // ignore: invalid_use_of_protected_member
+      expect(PiiMaskingController.instance.hasListeners, before);
+    });
+  });
+}

test/guards/no_extension_method_listeners_test.dart

@@ -0,0 +1,58 @@
+import 'dart:io';
+
+import 'package:flutter_test/flutter_test.dart';
+
+/// #1555: an extension method torn off twice gives two different closures, so
+/// `removeListener(_onX)` never removes what `addListener(_onX)` stored and the
+/// listener keeps its owner alive. Handlers passed to `addListener` /
+/// `removeListener` must be class members or a stored closure.
+void main() {
+  test('addListener / removeListener never take an extension method', () {
+    final extensionBody = RegExp(
+      r'^extension\s+\w+(?:<[^>]*>)?\s+on\s+[^{]+\{',
+      multiLine: true,
+    );
+    final methodDecl = RegExp(
+      r'^  (?:[\w<>?,\s]+\s)?(_?\w+)\s*\([^)]*\)\s*(?:async\s*)?(?:\{|=>)',
+      multiLine: true,
+    );
+    final listenerArg = RegExp(r'\b(?:add|remove)Listener\(\s*(_?\w+)\s*[,)]');
+
+    final extensionMethods = <String>{};
+    final files = <File>[];
+    for (final f in Directory('lib').listSync(recursive: true)) {
+      if (f is! File || !f.path.endsWith('.dart')) continue;
+      files.add(f);
+      final src = f.readAsStringSync();
+      for (final m in extensionBody.allMatches(src)) {
+        // Extensions are declared at the top level; their members are indented
+        // by two spaces up to the first closing brace in column zero.
+        final end = src.indexOf('\n}', m.end);
+        final body = src.substring(m.end, end < 0 ? src.length : end);
+        for (final d in methodDecl.allMatches(body)) {
+          extensionMethods.add(d.group(1)!);
+        }
+      }
+    }
+
+    // Comments may quote the pattern they warn about.
+    final commentLine = RegExp(r'^\s*//.*$', multiLine: true);
+
+    final offenders = <String>[];
+    for (final f in files) {
+      final code = f.readAsStringSync().replaceAll(commentLine, '');
+      for (final m in listenerArg.allMatches(code)) {
+        final name = m.group(1)!;
+        if (extensionMethods.contains(name)) offenders.add('${f.path}: $name');
+      }
+    }
+
+    expect(
+      offenders,
+      isEmpty,
+      reason: 'Extension methods passed to addListener / removeListener: '
+          '$offenders. Declare them in the class or keep one closure in a '
+          'field.',
+    );
+  });
+}