fix(firestore): allow null value to isEqualsTo & isNotEqualsTo in where() query

packages/cloud_firestore/cloud_firestore/example/integration_test/query_e2e.dart

@@ -1813,6 +1813,56 @@ void runQueryTests() {
         expect(snapshot.docs.length, equals(1));
         expect(snapshot.docs[0].get('foo'), equals(ref));
       });
+
+      testWidgets('pass `null` to `isEqualTo`', (_) async {
+        CollectionReference<Map<String, dynamic>> collection =
+            await initializeTest('where-null-isEqualTo');
+
+        await Future.wait([
+          collection.add({
+            'foo': 1,
+          }),
+          collection.add({'foo': 2}),
+          collection.add({
+            'foo': null,
+          }),
+          collection.add({
+            'foo': null,
+          }),
+        ]);
+
+        QuerySnapshot<Map<String, dynamic>> snapshot =
+            await collection.where('foo', isEqualTo: null).get();
+
+        expect(snapshot.docs.length, equals(2));
+        expect(snapshot.docs[0].get('foo'), equals(null));
+        expect(snapshot.docs[1].get('foo'), equals(null));
+      });
+
+      testWidgets('pass `null` to `isNotEqualTo`', (_) async {
+        CollectionReference<Map<String, dynamic>> collection =
+            await initializeTest('where-null-isNotEqualTo');
+
+        await Future.wait([
+          collection.add({
+            'foo': 11,
+          }),
+          collection.add({'foo': 11}),
+          collection.add({
+            'foo': null,
+          }),
+          collection.add({
+            'foo': null,
+          }),
+        ]);
+
+        QuerySnapshot<Map<String, dynamic>> snapshot =
+            await collection.where('foo', isNotEqualTo: null).get();
+
+        expect(snapshot.docs.length, equals(2));
+        expect(snapshot.docs[0].get('foo'), equals(11));
+        expect(snapshot.docs[1].get('foo'), equals(11));
+      });
     });
 
     group('Query.where() with Filter class', () {

packages/cloud_firestore/cloud_firestore/lib/src/query.dart

@@ -4,6 +4,10 @@
 
 part of cloud_firestore;
 
+/// Sentinel value to check whether user passed values explicitly through .where() method
+@internal
+const notSetQueryParam = Object();
+
 /// Represents a [Query] over the data at a particular location.
 ///
 /// Can construct refined [Query] objects by adding filters and ordering.
@@ -595,13 +599,13 @@ class _JsonQuery implements Query<Map<String, dynamic>> {
   @override
   Query<Map<String, dynamic>> where(
     Object fieldOrFilter, {
-    Object? isEqualTo,
-    Object? isNotEqualTo,
-    Object? isLessThan,
-    Object? isLessThanOrEqualTo,
-    Object? isGreaterThan,
-    Object? isGreaterThanOrEqualTo,
-    Object? arrayContains,
+    Object? isEqualTo = notSetQueryParam,
+    Object? isNotEqualTo = notSetQueryParam,
+    Object? isLessThan = notSetQueryParam,
+    Object? isLessThanOrEqualTo = notSetQueryParam,
+    Object? isGreaterThan = notSetQueryParam,
+    Object? isGreaterThanOrEqualTo = notSetQueryParam,
+    Object? arrayContains = notSetQueryParam,
     Iterable<Object?>? arrayContainsAny,
     Iterable<Object?>? whereIn,
     Iterable<Object?>? whereNotIn,
@@ -611,13 +615,13 @@ class _JsonQuery implements Query<Map<String, dynamic>> {
 
     if (fieldOrFilter is Filter) {
       assert(
-        isEqualTo == null &&
-            isNotEqualTo == null &&
-            isLessThan == null &&
-            isLessThanOrEqualTo == null &&
-            isGreaterThan == null &&
-            isGreaterThanOrEqualTo == null &&
-            arrayContains == null &&
+        identical(isEqualTo, notSetQueryParam) &&
+            identical(isNotEqualTo, notSetQueryParam) &&
+            identical(isLessThan, notSetQueryParam) &&
+            identical(isLessThanOrEqualTo, notSetQueryParam) &&
+            identical(isGreaterThan, notSetQueryParam) &&
+            identical(isGreaterThanOrEqualTo, notSetQueryParam) &&
+            identical(arrayContains, notSetQueryParam) &&
             arrayContainsAny == null &&
             whereIn == null &&
             whereNotIn == null &&
@@ -655,17 +659,29 @@ class _JsonQuery implements Query<Map<String, dynamic>> {
       conditions.add(condition);
     }
 
-    if (isEqualTo != null) addCondition(field, '==', isEqualTo);
-    if (isNotEqualTo != null) addCondition(field, '!=', isNotEqualTo);
-    if (isLessThan != null) addCondition(field, '<', isLessThan);
-    if (isLessThanOrEqualTo != null) {
+    if (!identical(isEqualTo, notSetQueryParam)) {
+      addCondition(field, '==', isEqualTo);
+    }
+
+    if (!identical(isNotEqualTo, notSetQueryParam)) {
+      addCondition(field, '!=', isNotEqualTo);
+    }
+
+    if (!identical(isLessThan, notSetQueryParam)) {
+      addCondition(field, '<', isLessThan);
+    }
+
+    if (!identical(isLessThanOrEqualTo, notSetQueryParam)) {
       addCondition(field, '<=', isLessThanOrEqualTo);
     }
-    if (isGreaterThan != null) addCondition(field, '>', isGreaterThan);
-    if (isGreaterThanOrEqualTo != null) {
+    if (!identical(isGreaterThan, notSetQueryParam)) {
+      addCondition(field, '>', isGreaterThan);
+    }
+
+    if (!identical(isGreaterThanOrEqualTo, notSetQueryParam)) {
       addCondition(field, '>=', isGreaterThanOrEqualTo);
     }
-    if (arrayContains != null) {
+    if (!identical(arrayContains, notSetQueryParam)) {
       addCondition(field, 'array-contains', arrayContains);
     }
     if (arrayContainsAny != null) {
@@ -952,13 +968,13 @@ class _WithConverterQuery<T extends Object?> implements Query<T> {
   @override
   Query<T> where(
     Object field, {
-    Object? isEqualTo,
-    Object? isNotEqualTo,
-    Object? isLessThan,
-    Object? isLessThanOrEqualTo,
-    Object? isGreaterThan,
-    Object? isGreaterThanOrEqualTo,
-    Object? arrayContains,
+    Object? isEqualTo = notSetQueryParam,
+    Object? isNotEqualTo = notSetQueryParam,
+    Object? isLessThan = notSetQueryParam,
+    Object? isLessThanOrEqualTo = notSetQueryParam,
+    Object? isGreaterThan = notSetQueryParam,
+    Object? isGreaterThanOrEqualTo = notSetQueryParam,
+    Object? arrayContains = notSetQueryParam,
     Iterable<Object?>? arrayContainsAny,
     Iterable<Object?>? whereIn,
     Iterable<Object?>? whereNotIn,

packages/cloud_firestore_odm/cloud_firestore_odm_generator/lib/src/collection_generator.dart

@@ -120,6 +120,7 @@ class CollectionGenerator
 // GENERATED CODE - DO NOT MODIFY BY HAND
 // ignore_for_file: unused_element, deprecated_member_use, deprecated_member_use_from_same_package, use_function_type_syntax_for_parameters, unnecessary_const, avoid_init_to_null, invalid_override_different_default_values_named, prefer_expression_function_bodies, annotate_overrides, require_trailing_commas, prefer_single_quotes, prefer_double_quotes, use_super_parameters, duplicate_ignore
 // ignore_for_file: type=lint
+// ignore_for_file: invalid_use_of_internal_member
     ''';
 
     yield '''

packages/cloud_firestore_odm/cloud_firestore_odm_generator/lib/src/templates/query_reference.dart

@@ -8,6 +8,13 @@ import 'package:analyzer/dart/element/type_provider.dart';
 
 import '../collection_data.dart';
 
+class _WhereType {
+  _WhereType(this.type, [this.defaultValue]);
+
+  final String type;
+  final String? defaultValue;
+}
+
 class QueryTemplate {
   QueryTemplate(this.data);
 
@@ -208,13 +215,13 @@ class ${data.queryReferenceImplName}
 
   ${data.queryReferenceInterfaceName} whereFieldPath(
     FieldPath fieldPath, {
-    Object? isEqualTo,
-    Object? isNotEqualTo,
-    Object? isLessThan,
-    Object? isLessThanOrEqualTo,
-    Object? isGreaterThan,
-    Object? isGreaterThanOrEqualTo,
-    Object? arrayContains,
+    Object? isEqualTo = notSetQueryParam,
+    Object? isNotEqualTo = notSetQueryParam,
+    Object? isLessThan = notSetQueryParam,
+    Object? isLessThanOrEqualTo = notSetQueryParam,
+    Object? isGreaterThan = notSetQueryParam,
+    Object? isGreaterThanOrEqualTo = notSetQueryParam,
+    Object? arrayContains = notSetQueryParam,
     List<Object?>? arrayContainsAny,
     List<Object?>? whereIn,
     List<Object?>? whereNotIn,
@@ -380,26 +387,49 @@ class ${data.queryReferenceImplName}
               ? '${field.type}'
               : '${field.type}?';
 
-      final operators = {
-        'isEqualTo': nullableType,
-        'isNotEqualTo': nullableType,
-        'isLessThan': nullableType,
-        'isLessThanOrEqualTo': nullableType,
-        'isGreaterThan': nullableType,
-        'isGreaterThanOrEqualTo': nullableType,
-        'isNull': 'bool?',
+      final operators = <String, _WhereType>{
+        'isEqualTo': isAbstract
+            ? _WhereType(nullableType)
+            : _WhereType('Object?', 'notSetQueryParam'),
+        'isNotEqualTo': isAbstract
+            ? _WhereType(nullableType)
+            : _WhereType('Object?', 'notSetQueryParam'),
+        'isLessThan': isAbstract
+            ? _WhereType(nullableType)
+            : _WhereType('Object?', 'notSetQueryParam'),
+        'isLessThanOrEqualTo': isAbstract
+            ? _WhereType(nullableType)
+            : _WhereType('Object?', 'notSetQueryParam'),
+        'isGreaterThan': isAbstract
+            ? _WhereType(nullableType)
+            : _WhereType('Object?', 'notSetQueryParam'),
+        'isGreaterThanOrEqualTo': isAbstract
+            ? _WhereType(nullableType)
+            : _WhereType('Object?', 'notSetQueryParam'),
+        'isNull': _WhereType('bool?'),
         if (field.type.isSupportedIterable) ...{
-          'arrayContains': data.libraryElement.typeProvider
-              .asNullable((field.type as InterfaceType).typeArguments.first),
-          'arrayContainsAny': nullableType,
+          'arrayContains': isAbstract
+              ? _WhereType(
+                  data.libraryElement.typeProvider
+                      .asNullable(
+                        (field.type as InterfaceType).typeArguments.first,
+                      )
+                      .toString(),
+                )
+              : _WhereType('Object?', 'notSetQueryParam'),
+          'arrayContainsAny': _WhereType(nullableType),
         } else ...{
-          'whereIn': 'List<${field.type}>?',
-          'whereNotIn': 'List<${field.type}>?',
+          'whereIn': _WhereType('List<${field.type}>?'),
+          'whereNotIn': _WhereType('List<${field.type}>?'),
         },
       };
 
-      final prototype =
-          operators.entries.map((e) => '${e.value} ${e.key},').join();
+      final prototype = operators.entries.map((e) {
+        if (e.value.defaultValue != null) {
+          return '${e.value.type} ${e.key} = ${e.value.defaultValue},';
+        }
+        return '${e.value.type} ${e.key},';
+      }).join();
 
       final perFieldToJson = data.perFieldToJson(field.name);
 
@@ -411,19 +441,22 @@ class ${data.queryReferenceImplName}
         } else if (e == 'arrayContainsAny') {
           return '$e: $e != null ? $perFieldToJson($e) as Iterable<Object>? : null,';
         } else if (e == 'arrayContains') {
-          var transform = '$e: $e != null ? ($perFieldToJson(';
+          final itemType =
+              (field.type as InterfaceType).typeArguments.first.toString();
+          final cast = itemType != 'Object?' ? ' as $itemType' : '';
+
+          var transform = '$e: $e != notSetQueryParam ? ($perFieldToJson(';
           if (field.type.isSet) {
-            transform += '{$e}';
+            transform += '{$e$cast}';
           } else {
-            transform += '[$e]';
+            transform += '[$e$cast]';
           }
-          return '$transform) as List?)!.single : null,';
+          return '$transform) as List?)!.single : notSetQueryParam,';
         } else {
-          return '$e: $e != null ? $perFieldToJson($e) : null,';
+          return '$e: $e != notSetQueryParam ? $perFieldToJson($e as ${field.type}) : notSetQueryParam,';
         }
       }).join();
 
-      // TODO support whereX(isEqual: null);
       // TODO handle JsonSerializable case change and JsonKey(name: ...)
 
       if (isAbstract) {

packages/cloud_firestore_odm/cloud_firestore_odm_generator/pubspec.yaml

@@ -15,7 +15,7 @@ dependencies:
   collection: ^1.15.0
   freezed_annotation: '>=1.0.0 <3.0.0'
   # Can be removed once this is fixed https://github.com/dart-lang/graphs/issues/86
-  graphs: '>=2.0.0 <2.3.0'
+  graphs: ^2.0.0
   json_annotation: ^4.8.1
   meta: ^1.8.0
   recase: ^4.0.0