fix(connections): editing a connection of a missing extension or driver explains why nothing opens (#1314)

lib/features/connections/connection_creation_flow.dart

@@ -1,3 +1,4 @@
+import 'package:flutter/foundation.dart' show visibleForTesting;
 import 'package:flutter/material.dart' as material;
 import 'package:querya_desktop/core/extensions/extension_driver_catalog.dart';
 import 'package:querya_desktop/core/extensions/models/extension_contributions.dart';
@@ -9,6 +10,7 @@ import 'package:querya_desktop/features/mongodb/mongodb_connection_form.dart';
 import 'package:querya_desktop/features/mysql/mysql_connection_form.dart';
 import 'package:querya_desktop/features/postgresql/postgresql_connection_form.dart';
 import 'package:querya_desktop/features/redis/redis_connection_form.dart';
+import 'package:querya_desktop/shared/widgets/app_toast.dart';
 
 export 'package:querya_desktop/features/connections/connection_edit_secrets.dart';
 
@@ -74,9 +76,29 @@ Future<ConnectionRow?> promptEditConnection(
 
   if (ExtensionDriverCatalog.isExtensionDriverConnection(existing)) {
     final manifest = ExtensionDriverCatalog.manifestForConnection(existing);
-    if (manifest == null) return null;
-    final driver = _driverForConnection(existing, manifest.contributedDrivers);
-    if (driver == null) return null;
+    if (manifest == null) {
+      // Not a silent nothing (#1314): say what is missing.
+      final who = existing.extensionId?.trim().isNotEmpty == true
+          ? 'The extension "${existing.extensionId!.trim()}"'
+          : 'The extension for "${existing.type}" connections';
+      _explain(
+        dialogContext,
+        '$who that provides "${existing.name}" is not installed or is '
+        'disabled. Install or enable it in the extension manager, then edit '
+        'the connection.',
+      );
+      return null;
+    }
+    final driver = driverForConnection(existing, manifest.contributedDrivers);
+    if (driver == null) {
+      _explain(
+        dialogContext,
+        'The extension "${manifest.id}" no longer provides the driver '
+        '"${existing.type}" that "${existing.name}" uses. Update or '
+        'reinstall the extension to edit it.',
+      );
+      return null;
+    }
     return showExtensionConnectionForm(
       dialogContext,
       manifest: manifest,
@@ -112,19 +134,44 @@ Future<ConnectionRow?> promptEditConnection(
         folderId: existing.folderId,
         initial: existing,
       ),
-    _ => null,
+    _ => _explainUnknownType(dialogContext, existing),
   };
 }
 
-DriverContribution? _driverForConnection(
+ConnectionRow? _explainUnknownType(
+  material.BuildContext context,
+  ConnectionRow existing,
+) {
+  _explain(
+    context,
+    'Unknown connection type "${existing.type}": "${existing.name}" cannot '
+    'be edited here.',
+  );
+  return null;
+}
+
+/// A short error toast on [context], when it is still mounted.
+void _explain(material.BuildContext context, String message) {
+  if (!context.mounted) return;
+  showAppToast(
+    context: context,
+    variant: AppToastVariant.error,
+    message: message,
+  );
+}
+
+/// The driver of [row] in [drivers]: the one whose id is the row's type, or,
+/// when the extension contributes exactly one, that one. Never a different
+/// driver of an extension that has several (#1314).
+@visibleForTesting
+DriverContribution? driverForConnection(
   ConnectionRow row,
   Iterable<DriverContribution> drivers,
 ) {
   final type = row.type.trim().toLowerCase();
-  DriverContribution? first;
-  for (final driver in drivers) {
-    first ??= driver;
+  final all = drivers.toList();
+  for (final driver in all) {
     if (driver.driverId.trim().toLowerCase() == type) return driver;
   }
-  return first;
+  return all.length == 1 ? all.single : null;
 }

test/features/connections/edit_extension_connection_test.dart

@@ -0,0 +1,82 @@
+import 'package:flutter/material.dart' as material;
+import 'package:flutter_test/flutter_test.dart';
+import 'package:querya_desktop/core/extensions/models/extension_contributions.dart';
+import 'package:querya_desktop/core/storage/local_db.dart';
+import 'package:querya_desktop/features/connections/connection_creation_flow.dart';
+
+import '../../support/querya_theme_test_shell.dart';
+
+/// #1314: editing a connection whose extension or driver is missing says so.
+ConnectionRow _row({String? extensionId, String type = 'clickhouse'}) =>
+    ConnectionRow(
+      id: 7,
+      type: type,
+      name: 'Warehouse',
+      extensionId: extensionId,
+      createdAt: '2026-01-01T00:00:00Z',
+    );
+
+void main() {
+  group('driverForConnection', () {
+    const a = DriverContribution(driverId: 'clickhouse', displayName: 'CH');
+    const b = DriverContribution(driverId: 'duckdb', displayName: 'Duck');
+
+    test('the driver of the row\'s type', () {
+      expect(driverForConnection(_row(type: 'duckdb'), [a, b]), b);
+      expect(driverForConnection(_row(type: 'ClickHouse'), [a, b]), a);
+    });
+
+    test('the only driver of an extension, whatever the row says', () {
+      expect(driverForConnection(_row(type: 'legacy'), [a]), a);
+    });
+
+    test('never another driver of an extension that has several', () {
+      expect(driverForConnection(_row(type: 'legacy'), [a, b]), isNull);
+      expect(driverForConnection(_row(), const []), isNull);
+    });
+  });
+
+  testWidgets('editing a connection of a missing extension explains it',
+      (t) async {
+    ConnectionRow? result = _row();
+    await t.pumpWidget(queryaThemeTestShell(
+      child: material.Builder(
+        builder: (context) => material.TextButton(
+          onPressed: () async => result = await promptEditConnection(
+              context, _row(extensionId: 'acme.warehouse-driver')),
+          child: const material.Text('edit'),
+        ),
+      ),
+    ));
+
+    await t.tap(find.text('edit'));
+    await t.pump();
+    await t.pump(const Duration(milliseconds: 300));
+
+    expect(result, isNull);
+    expect(find.textContaining('acme.warehouse-driver'), findsOneWidget);
+    expect(find.textContaining('not installed or is disabled'),
+        findsOneWidget);
+    await t.pump(const Duration(seconds: 6));
+  });
+
+  testWidgets('an unknown connection type explains it too', (t) async {
+    await t.pumpWidget(queryaThemeTestShell(
+      child: material.Builder(
+        builder: (context) => material.TextButton(
+          onPressed: () => promptEditConnection(context, _row(type: 'cobol')),
+          child: const material.Text('edit'),
+        ),
+      ),
+    ));
+
+    await t.tap(find.text('edit'));
+    await t.pump();
+    await t.pump(const Duration(milliseconds: 300));
+
+    // `cobol` is no built-in type and no extension has it.
+    expect(find.textContaining('Unknown connection type "cobol"'),
+        findsOneWidget);
+    await t.pump(const Duration(seconds: 6));
+  });
+}