fix(mongo): JSON filter cannot match ObjectId / DateTime fields

CHANGELOG.md

@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+- **Mongo JSON filter ObjectId / DateTime (#783)** — Document list filter parses Extended JSON (`$oid`, `$date`) and wraps a 24-character hex `_id` as `ObjectId`. A leftover string `_id` with zero matches shows how to write `{ "_id": { "$oid": "…" } }`.
 - **Postgres open-transaction probe (#787)** — `BEGIN` + `SELECT` does not assign an XID, so `pg_current_xact_id_if_assigned` stayed NULL (SQL-tab badge off; autocommit-off prepended a second `BEGIN`). The session tracks BEGIN/COMMIT/ROLLBACK and otherwise probes `pg_stat_activity.xact_start` (PG 9+). Implicit BEGIN when autocommit is off stays a separate `execute`.
 - **Postgres Table Browser paging (#788)** — Browse stays on `PgSessionMode.readOnly`. `SELECT` uses `ORDER BY` primary-key columns when a PK exists. Row totals come from `pg_class.reltuples` instead of a blocking `COUNT(*)` before first paint (stale estimates below the current page are ignored so Next still works). Save / REFRESH stay on `tableWrite`.
 - **Postgres timestamptz / bytea / jsonb / arrays (#789)** — Table Browser and SQL results encode cells as PG literals (ISO timestamps, `\x` hex for bytea, JSON text for jsonb, `{1,2,3}` for arrays) instead of `Object.toString`. Schema uses `udt_name` so `ARRAY` / `USER-DEFINED` round-trip through `formatLiteral`.

lib/features/mongodb/mongo_documents_view.dart

@@ -1,10 +1,10 @@
 import 'dart:async' show unawaited;
-import 'dart:convert';
 
 import 'package:flutter/material.dart' as material;
 import 'package:querya_desktop/core/database/destructive_sql_detector.dart';
 import 'package:querya_desktop/core/database/mongodb_connection.dart';
 import 'package:querya_desktop/core/database/mongodb_service.dart';
+import 'package:querya_desktop/features/mongodb/mongo_ejson.dart';
 import 'package:querya_desktop/features/mongodb/mongo_field_codec.dart';
 import 'package:querya_desktop/features/workspace/destructive_query_dialog.dart';
 import 'package:querya_desktop/features/workspace/grid_cell_popover_inspector.dart';
@@ -47,6 +47,7 @@ class _MongoDocumentsViewState extends material.State<MongoDocumentsView> {
 
   final _filterController = material.TextEditingController();
   Map<String, dynamic>? _activeFilter;
+  String? _emptyFilterHint;
 
   @override
   void initState() {
@@ -94,6 +95,11 @@ class _MongoDocumentsViewState extends material.State<MongoDocumentsView> {
         _totalCount = count;
         _documents = docs;
         _loading = false;
+        _emptyFilterHint = docs.isEmpty &&
+                _activeFilter != null &&
+                mongoFilterNeedsObjectIdHint(_activeFilter!)
+            ? kMongoFilterIdStringHint
+            : null;
       });
     } catch (e) {
       if (mounted) {
@@ -111,21 +117,23 @@ class _MongoDocumentsViewState extends material.State<MongoDocumentsView> {
       _activeFilter = null;
     } else {
       try {
-        _activeFilter = json.decode(text) as Map<String, dynamic>;
+        _activeFilter = mongoFilterFromJson(text);
       } catch (e) {
         setState(() {
           _error = 'Invalid JSON filter: $e';
         });
         return;
       }
     }
+    _emptyFilterHint = null;
     _skip = 0;
     _load();
   }
 
   void _clearFilter() {
     _filterController.clear();
     _activeFilter = null;
+    _emptyFilterHint = null;
     _skip = 0;
     _load();
   }
@@ -258,7 +266,8 @@ class _MongoDocumentsViewState extends material.State<MongoDocumentsView> {
               ? material.Center(
                   child: material.Padding(
                     padding: const material.EdgeInsets.all(48),
-                    child: const Text('No documents found').muted(),
+                    child: Text(_emptyFilterHint ?? 'No documents found')
+                        .muted(),
                   ),
                 )
               : material.ListView.separated(
@@ -303,7 +312,9 @@ class _MongoDocumentsViewState extends material.State<MongoDocumentsView> {
           material.Expanded(
             child: TextField(
               controller: _filterController,
-              placeholder: const Text('Filter (JSON) e.g. {"name": "John"}'),
+              placeholder: const Text(
+                r'Filter (JSON / EJSON) e.g. {"_id": {"$oid": "…"}}',
+              ),
               onSubmitted: (_) => _applyFilter(),
             ),
           ),

lib/features/mongodb/mongo_ejson.dart

@@ -22,3 +22,34 @@ Map<String, dynamic> mongoDocumentFromEjson(String text) {
   }
   return EJsonCodec.eJson2Doc(Map<String, dynamic>.from(decoded));
 }
+
+/// Hint when a find filter's `_id` is still a JSON string (not ObjectId).
+const kMongoFilterIdStringHint =
+    'No documents matched. If `_id` is an ObjectId, use '
+    r'{"_id": {"$oid": "…"}} or a 24-character hex `_id`.';
+
+/// Parses a find filter: Extended JSON (`$oid`, `$date`, …) plus a 24-char
+/// hex `_id` string wrapped as [ObjectId].
+Map<String, dynamic> mongoFilterFromJson(String text) {
+  final decoded = json.decode(text);
+  if (decoded is! Map) {
+    throw const FormatException('Filter JSON must be an object');
+  }
+  final raw = Map<String, dynamic>.from(decoded);
+  Map<String, dynamic> doc;
+  try {
+    doc = EJsonCodec.eJson2Doc(Map<String, dynamic>.from(raw));
+  } catch (_) {
+    doc = raw;
+  }
+  final id = doc['_id'];
+  if (id is String && ObjectId.isValidHexId(id)) {
+    doc['_id'] = ObjectId.fromHexString(id);
+  }
+  return doc;
+}
+
+/// True when `_id` is still a JSON string (hex wrap did not apply).
+bool mongoFilterNeedsObjectIdHint(Map<String, dynamic> filter) {
+  return filter['_id'] is String;
+}

test/features/mongodb/mongo_ejson_test.dart

@@ -55,4 +55,47 @@ void main() {
       );
     });
   });
+
+  group('mongoFilterFromJson', () {
+    test('24-char hex _id becomes ObjectId, not a String', () {
+      const hex = '507f1f77bcf86cd799439011';
+      final filter = mongoFilterFromJson('{"_id": "$hex"}');
+      expect(filter['_id'], isA<ObjectId>());
+      expect(filter['_id'], isNot(isA<String>()));
+      expect((filter['_id'] as ObjectId).oid, hex);
+      expect(mongoFilterNeedsObjectIdHint(filter), isFalse);
+    });
+
+    test('Extended JSON \$oid _id is ObjectId', () {
+      const hex = '507f191e810c19729de860ea';
+      final filter = mongoFilterFromJson(
+        '{"_id": {"\$oid": "$hex"}}',
+      );
+      expect(filter['_id'], isA<ObjectId>());
+      expect((filter['_id'] as ObjectId).oid, hex);
+    });
+
+    test('Extended JSON \$date is DateTime', () {
+      final filter = mongoFilterFromJson(
+        '{"created": {"\$date": "2024-01-15T12:30:00.000Z"}}',
+      );
+      expect(filter['created'], isA<DateTime>());
+      expect(
+        (filter['created'] as DateTime).toUtc(),
+        DateTime.utc(2024, 1, 15, 12, 30),
+      );
+    });
+
+    test('non-hex _id string stays a string and needs the ObjectId hint', () {
+      final filter = mongoFilterFromJson('{"_id": "not-an-objectid"}');
+      expect(filter['_id'], 'not-an-objectid');
+      expect(mongoFilterNeedsObjectIdHint(filter), isTrue);
+    });
+
+    test('query operators like \$gt are kept', () {
+      final filter = mongoFilterFromJson('{"age": {"\$gt": 5}}');
+      expect(filter['age'], isA<Map>());
+      expect((filter['age'] as Map)[r'$gt'], 5);
+    });
+  });
 }