feat(firestore): count() feature for counting documents without retrieving documents.

packages/cloud_firestore/cloud_firestore/example/test_driver/query_e2e.dart

@@ -7,6 +7,7 @@ import 'dart:math';
 
 import 'package:cloud_firestore/cloud_firestore.dart';
 import 'package:firebase_core/firebase_core.dart';
+import 'package:flutter/foundation.dart';
 import 'package:flutter_test/flutter_test.dart';
 
 void runQueryTests() {
@@ -1807,6 +1808,22 @@ void runQueryTests() {
         },
         timeout: const Timeout.factor(3),
       );
+
+      test('count()', () async {
+        final collection = await initializeTest('count');
+
+        await Future.wait([collection.add({'foo': 'bar'}), collection.add({'bar': 'baz'})]) ;
+
+        AggregateQuery query = collection.count();
+
+        AggregateQuerySnapshot snapshot = await query.get();
+
+        expect(
+          snapshot.count,
+          2,
+        );
+        // TODO(russellwheatley): remove when native code implemented
+      }, skip: !kIsWeb);
     });
   });
 }

packages/cloud_firestore/cloud_firestore/ios/cloud_firestore.podspec

@@ -24,17 +24,17 @@ Pod::Spec.new do |s|
   s.license          = { :file => '../LICENSE' }
   s.authors          = 'The Chromium Authors'
   s.source           = { :path => '.' }
-  
+
   s.source_files     = 'Classes/**/*.{h,m}'
   s.public_header_files = 'Classes/Public/*.h'
   s.private_header_files = 'Classes/Private/*.h'
 
-  s.ios.deployment_target = '10.0'
+  s.ios.deployment_target = '11.0'
   s.dependency 'Flutter'
 
   s.dependency 'firebase_core'
   s.dependency 'Firebase/Firestore', firebase_sdk_version
-  
+
   s.static_framework = true
   s.pod_target_xcconfig = {
     'GCC_PREPROCESSOR_DEFINITIONS' => "LIBRARY_VERSION=\\@\\\"#{library_version}\\\" LIBRARY_NAME=\\@\\\"flutter-fire-fst\\\"",

packages/cloud_firestore/cloud_firestore/lib/cloud_firestore.dart

@@ -17,6 +17,7 @@ import 'package:meta/meta.dart';
 
 export 'package:cloud_firestore_platform_interface/cloud_firestore_platform_interface.dart'
     show
+        AggregateSource,
         ListEquality,
         FieldPath,
         Blob,
@@ -46,3 +47,5 @@ part 'src/snapshot_metadata.dart';
 part 'src/transaction.dart';
 part 'src/utils/codec_utility.dart';
 part 'src/write_batch.dart';
+part 'src/aggregate_query.dart';
+part 'src/aggregate_query_snapshot.dart';

packages/cloud_firestore/cloud_firestore/lib/src/aggregate_query.dart

@@ -0,0 +1,12 @@
+part of cloud_firestore;
+
+class AggregateQuery {
+  AggregateQuery._(this._delegate) {
+    AggregateQueryPlatform.verifyExtends(_delegate);
+  }
+  final AggregateQueryPlatform _delegate;
+
+  Future<AggregateQuerySnapshot> get({AggregateSource source = AggregateSource.server}) async {
+    return AggregateQuerySnapshot._(await _delegate.get(source: source));
+  }
+}

packages/cloud_firestore/cloud_firestore/lib/src/aggregate_query_snapshot.dart

@@ -0,0 +1,10 @@
+part of cloud_firestore;
+
+class AggregateQuerySnapshot {
+  AggregateQuerySnapshot._(this._delegate) {
+    AggregateQuerySnapshotPlatform.verifyExtends(_delegate);
+  }
+  final AggregateQuerySnapshotPlatform _delegate;
+
+  int get count => _delegate.count;
+}

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

@@ -186,6 +186,8 @@ abstract class Query<T extends Object?> {
     required FromFirestore<R> fromFirestore,
     required ToFirestore<R> toFirestore,
   });
+
+  AggregateQuery count();
 }
 
 /// Represents a [Query] over the data at a particular location.
@@ -808,6 +810,11 @@ class _JsonQuery implements Query<Map<String, dynamic>> {
 
   @override
   int get hashCode => Object.hash(runtimeType, firestore, _delegate);
+
+  @override
+  AggregateQuery count() {
+    return AggregateQuery._(_delegate.count());
+  }
 }
 
 class _WithConverterQuery<T extends Object?> implements Query<T> {
@@ -970,4 +977,9 @@ class _WithConverterQuery<T extends Object?> implements Query<T> {
   @override
   int get hashCode =>
       Object.hash(runtimeType, _fromFirestore, _toFirestore, _originalQuery);
+
+  @override
+  AggregateQuery count() {
+    return _originalQuery.count();
+  }
 }

packages/cloud_firestore/cloud_firestore_platform_interface/lib/cloud_firestore_platform_interface.dart

@@ -24,6 +24,9 @@ export 'src/platform_interface/platform_interface_transaction.dart';
 export 'src/platform_interface/platform_interface_write_batch.dart';
 export 'src/platform_interface/platform_interface_load_bundle_task.dart';
 export 'src/platform_interface/platform_interface_load_bundle_task_snapshot.dart';
+export 'src/platform_interface/platform_interface_aggregate_query.dart';
+export 'src/platform_interface/platform_interface_aggregate_query_snapshot.dart';
+export 'src/aggregate_source.dart';
 export 'src/snapshot_metadata.dart';
 export 'src/source.dart';
 export 'src/load_bundle_task_state.dart';

packages/cloud_firestore/cloud_firestore_platform_interface/lib/src/aggregate_source.dart

@@ -0,0 +1,3 @@
+enum AggregateSource {
+  server,
+}

packages/cloud_firestore/cloud_firestore_platform_interface/lib/src/method_channel/method_channel_aggregate_query.dart

@@ -0,0 +1,29 @@
+import 'package:cloud_firestore_platform_interface/src/method_channel/utils/source.dart';
+import 'package:cloud_firestore_platform_interface/src/platform_interface/platform_interface_aggregate_query.dart';
+
+import 'method_channel_firestore.dart';
+import '../../cloud_firestore_platform_interface.dart';
+import '../aggregate_source.dart';
+import '../platform_interface/platform_interface_aggregate_query_snapshot.dart';
+
+class MethodChannelAggregateQuery extends AggregateQueryPlatform {
+  MethodChannelAggregateQuery(QueryPlatform query) : super(query);
+
+  @override
+  Future<AggregateQuerySnapshotPlatform> get({required AggregateSource source}) async {
+    final Map<String, dynamic>? data = await MethodChannelFirebaseFirestore
+        .channel
+        .invokeMapMethod<String, dynamic>(
+      'AggregateQuery#count',
+      <String, dynamic>{
+        'query': query,
+        'firestore': query.firestore,
+        'source': getAggregateSourceString(source),
+      },
+    );
+
+    return AggregateQuerySnapshotPlatform(
+       count: data!['count'] as int,
+    );
+  }
+}

packages/cloud_firestore/cloud_firestore_platform_interface/lib/src/method_channel/method_channel_query.dart

@@ -11,6 +11,7 @@ import 'package:cloud_firestore_platform_interface/src/internal/pointer.dart';
 import 'package:collection/collection.dart';
 import 'package:flutter/services.dart';
 
+import 'method_channel_aggregate_query.dart';
 import 'method_channel_firestore.dart';
 import 'method_channel_query_snapshot.dart';
 import 'utils/source.dart';
@@ -212,6 +213,13 @@ class MethodChannelQuery extends QueryPlatform {
     });
   }
 
+  @override
+  AggregateQueryPlatform count() {
+    return MethodChannelAggregateQuery(
+      this,
+    );
+  }
+
   @override
   bool operator ==(Object other) {
     return runtimeType == other.runtimeType &&

packages/cloud_firestore/cloud_firestore_platform_interface/lib/src/method_channel/utils/source.dart

@@ -3,6 +3,7 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+import 'package:cloud_firestore_platform_interface/src/aggregate_source.dart';
 import 'package:cloud_firestore_platform_interface/src/source.dart';
 
 /// Converts [Source] to [String]
@@ -16,3 +17,13 @@ String getSourceString(Source source) {
       return 'default';
   }
 }
+
+
+/// Converts [AggregateSource] to [String]
+String getAggregateSourceString(AggregateSource source) {
+  switch (source) {
+    case AggregateSource.server:
+    default:
+      return 'server';
+  }
+}

packages/cloud_firestore/cloud_firestore_platform_interface/lib/src/platform_interface/platform_interface_aggregate_query.dart

@@ -0,0 +1,27 @@
+import 'package:cloud_firestore_platform_interface/src/platform_interface/platform_interface_aggregate_query_snapshot.dart';
+import 'package:plugin_platform_interface/plugin_platform_interface.dart';
+import '../../cloud_firestore_platform_interface.dart';
+import '../aggregate_source.dart';
+
+abstract class AggregateQueryPlatform extends PlatformInterface {
+  AggregateQueryPlatform(this.query) : super(token: _token);
+
+  static final Object _token = Object();
+
+  /// Throws an [AssertionError] if [instance] does not extend
+  /// [AggregateQueryPlatform].
+  ///
+  /// This is used by the app-facing [AggregateQuery] to ensure that
+  /// the object in which it's going to delegate calls has been
+  /// constructed properly.
+  static void verifyExtends(AggregateQueryPlatform instance) {
+      PlatformInterface.verifyToken(instance, _token);
+  }
+
+  final QueryPlatform query;
+
+  Future<AggregateQuerySnapshotPlatform> get({required AggregateSource source}) async {
+    throw UnimplementedError('get() is not implemented');
+  }
+
+}

packages/cloud_firestore/cloud_firestore_platform_interface/lib/src/platform_interface/platform_interface_aggregate_query_snapshot.dart

@@ -0,0 +1,21 @@
+import 'package:plugin_platform_interface/plugin_platform_interface.dart';
+
+class AggregateQuerySnapshotPlatform extends PlatformInterface {
+  AggregateQuerySnapshotPlatform({required count}) : _count = count, super(token: _token);
+
+  static final Object _token = Object();
+
+  /// Throws an [AssertionError] if [instance] does not extend
+  /// [AggregateQuerySnapshotPlatform].
+  ///
+  /// This is used by the app-facing [AggregateQuerySnapshot] to ensure that
+  /// the object in which it's going to delegate calls has been
+  /// constructed properly.
+  static void verifyExtends(AggregateQuerySnapshotPlatform instance) {
+    PlatformInterface.verifyToken(instance, _token);
+  }
+
+  final int _count;
+
+  int get count => _count;
+}

packages/cloud_firestore/cloud_firestore_platform_interface/lib/src/platform_interface/platform_interface_firestore.dart

@@ -23,6 +23,8 @@ import 'platform_interface_query.dart';
 import 'platform_interface_query_snapshot.dart';
 import 'platform_interface_transaction.dart';
 import 'platform_interface_write_batch.dart';
+import 'platform_interface_aggregate_query.dart';
+import 'platform_interface_aggregate_query_snapshot.dart';
 
 /// Defines an interface to work with Cloud Firestore on web and mobile
 abstract class FirebaseFirestorePlatform extends PlatformInterface {

packages/cloud_firestore/cloud_firestore_platform_interface/lib/src/platform_interface/platform_interface_query.dart

@@ -228,4 +228,8 @@ abstract class QueryPlatform extends PlatformInterface {
   QueryPlatform where(List<List<dynamic>> conditions) {
     throw UnimplementedError('where() is not implemented');
   }
+
+  AggregateQueryPlatform count(){
+    throw UnimplementedError('count() is not implemented');
+  }
 }

packages/cloud_firestore/cloud_firestore_web/lib/src/aggregate_query_web.dart

@@ -0,0 +1,31 @@
+// ignore_for_file: require_trailing_commas
+// Copyright 2017, the Chromium project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'package:cloud_firestore_platform_interface/cloud_firestore_platform_interface.dart';
+
+import 'interop/firestore.dart' as firestore_interop;
+
+/// Web implementation for Firestore [AggregateQueryPlatform].
+class AggregateQueryWeb extends AggregateQueryPlatform {
+  /// instance of Firestore from the web plugin
+  // final firestore_interop.Firestore firestoreWeb;
+
+  /// instance of DocumentReference from the web plugin
+  final firestore_interop.AggregateQuery _delegate;
+  final firestore_interop.Query _webQuery;
+
+  /// Creates an instance of [DocumentReferenceWeb] which represents path
+  /// at [pathComponents] and uses implementation of [firestoreWeb]
+  AggregateQueryWeb(
+  QueryPlatform query, this._webQuery): _delegate = firestore_interop.AggregateQuery(_webQuery), super(query);
+
+  @override
+  Future<AggregateQuerySnapshotPlatform> get({required AggregateSource source}) async {
+    // There isn't a source option on web
+    firestore_interop.AggregateQuerySnapshot snapshot = await _delegate.get();
+
+    return AggregateQuerySnapshotPlatform(count: snapshot.count);
+  }
+}

packages/cloud_firestore/cloud_firestore_web/lib/src/interop/firestore.dart

@@ -772,3 +772,29 @@ abstract class FieldValue {
   static final FieldValue _serverTimestamp = _FieldValueServerTimestamp();
   static final FieldValue _delete = _FieldValueDelete();
 }
+
+class AggregateQuery {
+  AggregateQuery(Query query) :  _jsQuery = query.jsObject;
+  final firestore_interop.QueryJsImpl _jsQuery;
+  Future<AggregateQuerySnapshot> get() async {
+    return handleThenable<firestore_interop.AggregateQuerySnapshotJsImpl>(
+        firestore_interop.getCountFromServer(_jsQuery))
+        .then(AggregateQuerySnapshot.getInstance);
+  }
+}
+
+class AggregateQuerySnapshot
+    extends JsObjectWrapper<firestore_interop.AggregateQuerySnapshotJsImpl> {
+  static final _expando = Expando<AggregateQuerySnapshot>();
+  late final Map<String, Object> _data;
+  /// Creates a new Firestore from a [jsObject].
+  static AggregateQuerySnapshot getInstance(firestore_interop.AggregateQuerySnapshotJsImpl jsObject) {
+
+    return _expando[jsObject] ??= AggregateQuerySnapshot._fromJsObject(jsObject);
+  }
+
+  AggregateQuerySnapshot._fromJsObject(firestore_interop.AggregateQuerySnapshotJsImpl jsObject)
+      : _data = Map.from(dartify(jsObject.data())), super.fromJsObject(jsObject);
+
+  int get count => _data['count']! as int;
+}

packages/cloud_firestore/cloud_firestore_web/lib/src/interop/firestore_interop.dart

@@ -651,3 +651,15 @@ external Object get arrayRemove;
 
 @JS()
 external Object get arrayUnion;
+
+
+@JS()
+external PromiseJsImpl<AggregateQuerySnapshotJsImpl> getCountFromServer(
+    QueryJsImpl query,
+    );
+
+
+@JS('AggregateQuerySnapshot')
+abstract class AggregateQuerySnapshotJsImpl {
+  external Map<String, Object> data();
+}

packages/cloud_firestore/cloud_firestore_web/lib/src/query_web.dart

@@ -7,6 +7,7 @@ import 'package:cloud_firestore_platform_interface/cloud_firestore_platform_inte
 import 'package:collection/collection.dart';
 import 'package:cloud_firestore_web/src/utils/encode_utility.dart';
 
+import 'aggregate_query_web.dart';
 import 'internals.dart';
 import 'interop/firestore.dart' as firestore_interop;
 import 'utils/web_utils.dart';
@@ -232,4 +233,9 @@ class QueryWeb extends QueryPlatform {
       'where': conditions,
     });
   }
+
+  @override
+  AggregateQueryPlatform count(){
+    return AggregateQueryWeb(this, _webQuery);
+  }
 }

packages/firebase_core/firebase_core_web/lib/src/firebase_sdk_version.dart

@@ -6,4 +6,4 @@
 part of firebase_core_web;
 
 /// The currently supported Firebase JS SDK version.
-const String supportedFirebaseJsSdkVersion = '9.9.0';
+const String supportedFirebaseJsSdkVersion = '9.11.0';