feat: Apply team lints to core package (#334)

* Add analyzer file to core package

* Apply team lint rules to core package

* clean up analyzer warnings in stream chat flutter

* remove unused line

* add ignore

* sync analysis options

* [Core -> MessageWidget] Fix variable dynamic types

Signed-off-by: Sahil Kumar <[email protected]>

Co-authored-by: Salvatore Giordano <[email protected]>
Co-authored-by: Sahil Kumar <[email protected]>

packages/stream_chat/analysis_options.yaml

@@ -1,11 +1,11 @@
 analyzer:
-  exclude: 
+  exclude:
     - lib/**/*.g.dart
     - lib/**/*.freezed.dart
     - example/*
     - test/*
-linter: 
+linter:
-  rules: 
+  rules:
     - always_use_package_imports
     - avoid_empty_else
     - avoid_relative_lib_imports
@@ -14,7 +14,6 @@ linter:
     - cancel_subscriptions
     - close_sinks
     - control_flow_in_finally
-    - diagnostic_describe_all_properties
     - empty_statements
     - hash_and_equals
     - invariant_booleans
@@ -33,7 +32,6 @@ linter:
     - use_key_in_widget_constructors
     - valid_regexps
     - always_declare_return_types
-    - always_put_required_named_parameters_first
     - always_require_non_null_named_parameters
     - annotate_overrides
     - avoid_bool_literals_in_conditional_expressions

packages/stream_chat/lib/src/api/channel.dart

@@ -1210,9 +1210,10 @@ class ChannelClientState {
     this._channel,
     ChannelState channelState,
     //ignore: unnecessary_parenthesis
-  ) : _debouncedUpdatePersistenceChannelState = ((ChannelState state) {
+  ) : _debouncedUpdatePersistenceChannelState = ((ChannelState state) =>
-          _channel?._client?.chatPersistenceClient?.updateChannelState(state);
+                _channel?._client?.chatPersistenceClient
-        }).debounced(const Duration(seconds: 1)) {
+                    ?.updateChannelState(state))
+            .debounced(const Duration(seconds: 1)) {
     retryQueue = RetryQueue(
       channel: _channel,
       logger: Logger('RETRY QUEUE ${_channel.cid}'),

packages/stream_chat_flutter_core/analysis_options.yaml

@@ -0,0 +1,145 @@
+analyzer:
+  exclude:
+    - lib/**/*.g.dart
+    - lib/**/*.freezed.dart
+    - example/*
+    - test/*
+linter:
+  rules:
+    - always_use_package_imports
+    - avoid_empty_else
+    - avoid_relative_lib_imports
+    - avoid_slow_async_io
+    - avoid_types_as_parameter_names
+    - cancel_subscriptions
+    - close_sinks
+    - control_flow_in_finally
+    - empty_statements
+    - hash_and_equals
+    - invariant_booleans
+    - iterable_contains_unrelated_type
+    - list_remove_unrelated_type
+    - literal_only_boolean_expressions
+    - no_adjacent_strings_in_list
+    - no_duplicate_case_values
+    - no_logic_in_create_state
+    - prefer_void_to_null
+    - test_types_in_equals
+    - throw_in_finally
+    - unnecessary_statements
+    - unrelated_type_equality_checks
+    - omit_local_variable_types
+    - use_key_in_widget_constructors
+    - valid_regexps
+    - always_declare_return_types
+    - always_require_non_null_named_parameters
+    - annotate_overrides
+    - avoid_bool_literals_in_conditional_expressions
+    - avoid_catching_errors
+    - avoid_init_to_null
+    - avoid_null_checks_in_equality_operators
+    - avoid_positional_boolean_parameters
+    - avoid_private_typedef_functions
+    - avoid_redundant_argument_values
+    - avoid_return_types_on_setters
+    - avoid_returning_null
+    - avoid_returning_null_for_void
+    - avoid_shadowing_type_parameters
+    - avoid_single_cascade_in_expression_statements
+    - avoid_unnecessary_containers
+    - avoid_unused_constructor_parameters
+    - await_only_futures
+    - camel_case_extensions
+    - camel_case_types
+    - cascade_invocations
+
+    - constant_identifier_names
+    - curly_braces_in_flow_control_structures
+    - directives_ordering
+    - empty_catches
+    - empty_constructor_bodies
+    - exhaustive_cases
+    - file_names
+    - implementation_imports
+    - join_return_with_assignment
+    - leading_newlines_in_multiline_strings
+    - library_names
+    - library_prefixes
+    - lines_longer_than_80_chars
+    - missing_whitespace_between_adjacent_strings
+    - non_constant_identifier_names
+    - null_closures
+    - one_member_abstracts
+    - only_throw_errors
+    - package_api_docs
+    - package_prefixed_library_names
+    - parameter_assignments
+    - prefer_adjacent_string_concatenation
+    - prefer_asserts_in_initializer_lists
+    - prefer_asserts_with_message
+    - prefer_collection_literals
+    - prefer_conditional_assignment
+    - prefer_const_constructors
+    - prefer_const_constructors_in_immutables
+    - prefer_const_declarations
+    - prefer_const_literals_to_create_immutables
+    - prefer_constructors_over_static_methods
+    - prefer_contains
+    - prefer_equal_for_default_values
+    - prefer_expression_function_bodies
+    - prefer_final_fields
+    - prefer_final_in_for_each
+    - prefer_final_locals
+    - prefer_function_declarations_over_variables
+    - prefer_generic_function_type_aliases
+    - prefer_if_elements_to_conditional_expressions
+    - prefer_if_null_operators
+    - prefer_initializing_formals
+    - prefer_inlined_adds
+    - prefer_int_literals
+    - prefer_interpolation_to_compose_strings
+    - prefer_is_empty
+    - prefer_is_not_empty
+    - prefer_is_not_operator
+    - prefer_null_aware_operators
+    - prefer_single_quotes
+    - prefer_spread_collections
+    - prefer_typing_uninitialized_variables
+    - provide_deprecation_message
+    - public_member_api_docs
+    - recursive_getters
+    - sized_box_for_whitespace
+    - slash_for_doc_comments
+    - sort_child_properties_last
+    - sort_constructors_first
+    - sort_unnamed_constructors_first
+
+    - type_annotate_public_apis
+    - type_init_formals
+    - unnecessary_await_in_return
+    - unnecessary_brace_in_string_interps
+    - unnecessary_const
+    - unnecessary_getters_setters
+    - unnecessary_lambdas
+    - unnecessary_new
+    - unnecessary_null_aware_assignments
+    - unnecessary_null_in_if_null_operators
+    - unnecessary_nullable_for_final_variable_declarations
+    - unnecessary_parenthesis
+    - unnecessary_raw_strings
+    - unnecessary_string_escapes
+    - unnecessary_string_interpolations
+    - unnecessary_this
+    - use_is_even_rather_than_modulo
+    - use_late_for_private_fields_and_variables
+    - use_rethrow_when_possible
+    - use_setters_to_change_properties
+    - use_to_and_as_if_applicable
+    - package_names
+    - sort_pub_dependencies
+
+    # To be added when null-safe:
+    # - cast_nullable_to_non_nullable
+    #- unnecessary_null_checks
+    # - tighten_type_of_initializing_formals
+    # - null_check_on_nullable_type_parameter

packages/stream_chat_flutter_core/lib/src/channel_list_core.dart

@@ -5,11 +5,11 @@ import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:stream_chat/stream_chat.dart';
 import 'package:stream_chat_flutter_core/src/channels_bloc.dart';
+import 'package:stream_chat_flutter_core/src/stream_chat_core.dart';
 import 'package:stream_chat_flutter_core/src/typedef.dart';
 
-import 'stream_chat_core.dart';
+/// [ChannelListCore] is a simplified class that allows fetching a list of
-
+/// channels while exposing UI builders.
-/// [ChannelListCore] is a simplified class that allows fetching a list of channels while exposing UI builders.
 /// A [ChannelListController] is used to reload and paginate data.
 ///
 ///
@@ -52,10 +52,11 @@ import 'stream_chat_core.dart';
 /// }
 /// ```
 ///
-/// Make sure to have a [StreamChatCore] ancestor in order to provide the information about the channels.
+/// Make sure to have a [StreamChatCore] ancestor in order to provide the
+/// information about the channels.
 class ChannelListCore extends StatefulWidget {
   /// Instantiate a new ChannelListView
-  ChannelListCore({
+  const ChannelListCore({
     Key key,
     @required this.errorBuilder,
     @required this.emptyBuilder,
@@ -65,18 +66,31 @@ class ChannelListCore extends StatefulWidget {
     this.options,
     this.sort,
     this.pagination = const PaginationParams(
-      offset: 0,
       limit: 25,
     ),
     this.channelListController,
-  })  : assert(errorBuilder != null),
+  })  : assert(
-        assert(emptyBuilder != null),
+          errorBuilder != null,
-        assert(loadingBuilder != null),
+          'Parameter errorBuilder should not be null',
-        assert(listBuilder != null),
+        ),
+        assert(
+          emptyBuilder != null,
+          'Parameter emptyBuilder should not be null',
+        ),
+        assert(
+          loadingBuilder != null,
+          'Parameter loadingBuilder should not be null',
+        ),
+        assert(
+          listBuilder != null,
+          'Parameter listBuilder should not be null',
+        ),
         super(key: key);
 
   /// A [ChannelListController] allows reloading and pagination.
-  /// Use [ChannelListController.loadData] and [ChannelListController.paginateData] respectively for reloading and pagination.
+  /// Use [ChannelListController.loadData] and
+  /// [ChannelListController.paginateData] respectively for reloading and
+  /// pagination.
   final ChannelListController channelListController;
 
   /// The builder that will be used in case of error
@@ -103,9 +117,10 @@ class ChannelListCore extends StatefulWidget {
   final Map<String, dynamic> options;
 
   /// The sorting used for the channels matching the filters.
-  /// Sorting is based on field and direction, multiple sorting options can be provided.
+  /// Sorting is based on field and direction, multiple sorting options can be
-  /// You can sort based on last_updated, last_message_at, updated_at, created_at or member_count.
+  /// provided.
-  /// Direction can be ascending or descending.
+  /// You can sort based on last_updated, last_message_at, updated_at, created
+  /// _at or member_count. Direction can be ascending or descending.
   final List<SortOption<ChannelModel>> sort;
 
   /// Pagination parameters
@@ -128,24 +143,23 @@ class _ChannelListCoreState extends State<ChannelListCore> {
 
   StreamBuilder<List<Channel>> _buildListView(
     ChannelsBlocState channelsBlocState,
-  ) {
+  ) =>
-    return StreamBuilder<List<Channel>>(
+      StreamBuilder<List<Channel>>(
-      stream: channelsBlocState.channelsStream,
+        stream: channelsBlocState.channelsStream,
-      builder: (context, snapshot) {
+        builder: (context, snapshot) {
-        if (snapshot.hasError) {
+          if (snapshot.hasError) {
-          return _buildErrorWidget(snapshot, context, channelsBlocState);
+            return _buildErrorWidget(snapshot, context, channelsBlocState);
-        }
+          }
-        if (!snapshot.hasData) {
+          if (!snapshot.hasData) {
-          return widget.loadingBuilder(context);
+            return widget.loadingBuilder(context);
-        }
+          }
-        final channels = snapshot.data;
+          final channels = snapshot.data;
-        if (channels.isEmpty) {
+          if (channels.isEmpty) {
-          return widget.emptyBuilder(context);
+            return widget.emptyBuilder(context);
-        }
+          }
-        return widget.listBuilder(context, channels);
+          return widget.listBuilder(context, channels);
-      },
+        },
-    );
+      );
-  }
 
   Widget _buildErrorWidget(
     AsyncSnapshot<List<Channel>> snapshot,
@@ -223,14 +237,15 @@ class _ChannelListCoreState extends State<ChannelListCore> {
   }
 }
 
-/// Controller used for loading more data and controlling pagination in [ChannelListCore].
+/// Controller used for loading more data and controlling pagination in
+/// [ChannelListCore].
 class ChannelListController {
-  /// This function calls Stream's servers to load a list of channels. If there is existing data,
+  /// This function calls Stream's servers to load a list of channels.
-  /// calling this function causes a reload.
+  /// If there is existing data, calling this function causes a reload.
   AsyncCallback loadData;
 
-  /// This function is used to load another page of data. Note, [loadData] should be
+  /// This function is used to load another page of data. Note, [loadData]
-  /// used to populate the initial page of data. Calling [paginateData] performs a query
+  /// should be used to populate the initial page of data. Calling
-  /// to load subsequent pages.
+  /// [paginateData] performs a query to load subsequent pages.
   AsyncCallback paginateData;
 }

packages/stream_chat_flutter_core/lib/src/channels_bloc.dart

@@ -1,5 +1,6 @@
 import 'dart:async';
 
+import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:rxdart/rxdart.dart';
 import 'package:stream_chat/stream_chat.dart';
@@ -16,26 +17,29 @@ import 'package:stream_chat_flutter_core/src/stream_chat_core.dart';
 ///
 /// API docs: https://getstream.io/chat/docs/flutter-dart/query_channels/
 class ChannelsBloc extends StatefulWidget {
-  /// Creates a new [ChannelsBloc]. The parameter [child] must be supplied and not null.
+  /// Creates a new [ChannelsBloc]. The parameter [child] must be supplied and
+  /// not null.
   const ChannelsBloc({
     Key key,
     @required this.child,
     this.lockChannelsOrder = false,
     this.channelsComparator,
     this.shouldAddChannel,
-  })  : assert(child != null),
+  })  : assert(child != null, 'Parameter child should not be null.'),
         super(key: key);
 
   /// The widget child
   final Widget child;
 
-  /// Set this to true to prevent channels to be brought to the top of the list when a new message arrives
+  /// Set this to true to prevent channels to be brought to the top of the list
+  /// when a new message arrives
   final bool lockChannelsOrder;
 
   /// Comparator used to sort the channels when a message.new event is received
   final Comparator<Channel> channelsComparator;
 
-  /// Function used to evaluate if a channel should be added to the list when a message.new event is received
+  /// Function used to evaluate if a channel should be added to the list when a
+  /// message.new event is received
   final bool Function(Event) shouldAddChannel;
 
   @override
@@ -170,13 +174,14 @@ class ChannelsBlocState extends State<ChannelsBloc>
         _channelsController.add(newChannels);
       }
     }));
-
+    // ignore: cascade_invocations
     _subscriptions.add(client
         .on(
       EventType.channelDeleted,
       EventType.notificationRemovedFromChannel,
     )
         .listen((e) {
+      // ignore: cascade_invocations
       final channel = e.channel;
       _channelsController.add(List.from(
           (channels ?? [])..removeWhere((c) => c.cid == channel.cid)));

packages/stream_chat_flutter_core/lib/src/lazy_load_scroll_view.dart

@@ -1,13 +1,14 @@
 import 'package:flutter/foundation.dart';
 import 'package:flutter/widgets.dart';
 
+// ignore: constant_identifier_names
 enum _LoadingStatus { LOADING, STABLE }
 
 /// Wrapper around a [Scrollable] which triggers [onEndOfPage]/[onStartOfPage] the Scrollable
 /// reaches to the start or end of the view extent.
 class LazyLoadScrollView extends StatefulWidget {
-  /// Creates a new instance of [LazyLoadScrollView]. The parameter [child] must be
+  /// Creates a new instance of [LazyLoadScrollView]. The parameter [child]
-  /// supplied and not null.
+  /// must be supplied and not null.
   const LazyLoadScrollView({
     Key key,
     @required this.child,
@@ -17,7 +18,7 @@ class LazyLoadScrollView extends StatefulWidget {
     this.onPageScrollEnd,
     this.onInBetweenOfPage,
     this.scrollOffset = 100,
-  })  : assert(child != null),
+  })  : assert(child != null, 'Parameter child should not be null'),
         super(key: key);
 
   /// The [Widget] that this widget watches for changes on
@@ -47,15 +48,13 @@ class LazyLoadScrollView extends StatefulWidget {
 
 class _LazyLoadScrollViewState extends State<LazyLoadScrollView> {
   _LoadingStatus _loadMoreStatus = _LoadingStatus.STABLE;
-  double _scrollPosition = 0.0;
+  double _scrollPosition = 0;
 
   @override
-  Widget build(BuildContext context) {
+  Widget build(BuildContext context) => NotificationListener(
-    return NotificationListener(
+        onNotification: _onNotification,
-      child: widget.child,
+        child: widget.child,
-      onNotification: _onNotification,
+      );
-    );
-  }
 
   bool _onNotification(Notification notification) {
     if (notification is ScrollStartNotification) {

packages/stream_chat_flutter_core/lib/src/message_list_core.dart

@@ -1,12 +1,15 @@
 import 'dart:async';
 
 import 'package:flutter/cupertino.dart';
+import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:stream_chat/stream_chat.dart';
+import 'package:stream_chat_flutter_core/src/stream_channel.dart';
 import 'package:stream_chat_flutter_core/src/typedef.dart';
-import 'stream_channel.dart';
 
-/// [MessageListCore] is a simplified class that allows fetching a list of messages while exposing UI builders.
+/// [MessageListCore] is a simplified class that allows fetching a list of
+/// messages while exposing UI builders.
+///
 /// A [MessageListController] is used to paginate data.
 ///
 /// ```dart
@@ -50,12 +53,14 @@ import 'stream_channel.dart';
 /// ```
 ///
 ///
-/// Make sure to have a [StreamChannel] ancestor in order to provide the information about the channels.
+/// Make sure to have a [StreamChannel] ancestor in order to provide the
+/// information about the channels.
+///
 /// The widget uses a [ListView.custom] to render the list of channels.
 ///
 class MessageListCore extends StatefulWidget {
   /// Instantiate a new [MessageListView].
-  MessageListCore({
+  const MessageListCore({
     Key key,
     @required this.loadingBuilder,
     @required this.emptyBuilder,
@@ -65,10 +70,16 @@ class MessageListCore extends StatefulWidget {
     this.parentMessage,
     this.messageListController,
     this.messageFilter,
-  })  : assert(loadingBuilder != null),
+  })  : assert(loadingBuilder != null, 'loadingBuilder should not be null'),
-        assert(emptyBuilder != null),
+        assert(emptyBuilder != null, 'emptyBuilder should not be null'),
-        assert(messageListBuilder != null),
+        assert(
-        assert(errorWidgetBuilder != null),
+          messageListBuilder != null,
+          'messageListBuilder should not be null',
+        ),
+        assert(
+          errorWidgetBuilder != null,
+          'errorWidgetBuilder should not be null',
+        ),
         super(key: key);
 
   /// A [MessageListController] allows pagination.
@@ -84,12 +95,15 @@ class MessageListCore extends StatefulWidget {
   /// Function used to build an empty widget
   final WidgetBuilder emptyBuilder;
 
-  /// Callback triggered when an error occurs while performing the given request.
+  /// Callback triggered when an error occurs while performing the given
-  /// This parameter can be used to display an error message to users in the event
+  /// request.
-  /// of a connection failure.
+  ///
+  /// This parameter can be used to display an error message to users in the
+  /// event of a connection failure.
   final ErrorBuilder errorWidgetBuilder;
 
-  /// If true will show a scroll to bottom message when there are new messages and the scroll offset is not zero
+  /// If true will show a scroll to bottom message when there are new messages
+  /// and the scroll offset is not zero.
   final bool showScrollToBottom;
 
   /// If the current message belongs to a `thread`, this property represents the
@@ -112,11 +126,7 @@ class _MessageListCoreState extends State<MessageListCore> {
 
   OwnUser get _currentUser => streamChannel.channel.client.state.user;
 
-  int initialIndex;
-  double initialAlignment;
-
   List<Message> messages = <Message>[];
-
   bool initialMessageHighlightComplete = false;
 
   @override

packages/stream_chat_flutter_core/lib/src/message_search_bloc.dart

@@ -1,8 +1,7 @@
 import 'package:flutter/material.dart';
 import 'package:rxdart/rxdart.dart';
 import 'package:stream_chat/stream_chat.dart';
-
+import 'package:stream_chat_flutter_core/src/stream_chat_core.dart';
-import 'stream_chat_core.dart';
 
 /// [MessageSearchBloc] is used to manage a list of messages with pagination.
 /// This class can be used to load messages, perform queries, etc.
@@ -16,7 +15,7 @@ class MessageSearchBloc extends StatefulWidget {
   const MessageSearchBloc({
     Key key,
     @required this.child,
-  })  : assert(child != null),
+  })  : assert(child != null, 'Parameter child should not be null.'),
         super(key: key);
 
   /// The widget child

packages/stream_chat_flutter_core/lib/src/message_search_list_core.dart

@@ -1,13 +1,15 @@
 import 'dart:convert';
 
+import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:stream_chat/stream_chat.dart';
+import 'package:stream_chat_flutter_core/src/message_search_bloc.dart';
 import 'package:stream_chat_flutter_core/src/typedef.dart';
-import 'message_search_bloc.dart';
 
 ///
-/// [MessageSearchListCore] is a simplified class that allows searching for messages across channels while exposing UI builders.
+/// [MessageSearchListCore] is a simplified class that allows searching for
-/// A [MessageSearchListController] is used to load and paginate data.
+///  messages across channels while exposing UI builders.
+///  A [MessageSearchListController] is used to load and paginate data.
 ///
 /// ```dart
 /// class MessageSearchPage extends StatelessWidget {
@@ -28,7 +30,8 @@ import 'message_search_bloc.dart';
 /// }
 /// ```
 ///
-/// Make sure to have a [MessageSearchBloc] ancestor in order to provide the information about the messages.
+/// Make sure to have a [MessageSearchBloc] ancestor in order to provide the
+/// information about the messages.
 /// The widget uses a [ListView.separated] to render the list of messages.
 ///
 class MessageSearchListCore extends StatefulWidget {
@@ -50,14 +53,16 @@ class MessageSearchListCore extends StatefulWidget {
     this.paginationParams,
     this.messageFilters,
     this.messageSearchListController,
-  })  : assert(emptyBuilder != null),
+  })  : assert(emptyBuilder != null, 'emptyBuilder should not be null'),
-        assert(errorBuilder != null),
+        assert(errorBuilder != null, 'errorBuilder should not be null'),
-        assert(loadingBuilder != null),
+        assert(loadingBuilder != null, 'loadingBuilder should not be null'),
-        assert(childBuilder != null),
+        assert(childBuilder != null, 'childBuilder should not be null'),
         super(key: key);
 
   /// A [MessageSearchListController] allows reloading and pagination.
-  /// Use [MessageSearchListController.loadData] and [MessageSearchListController.paginateData] respectively for reloading and pagination.
+  /// Use [MessageSearchListController.loadData] and
+  /// [MessageSearchListController.paginateData] respectively for reloading and
+  /// pagination.
   final MessageSearchListController messageSearchListController;
 
   /// Message String to search on
@@ -69,9 +74,10 @@ class MessageSearchListCore extends StatefulWidget {
   final Map<String, dynamic> filters;
 
   /// The sorting used for the channels matching the filters.
-  /// Sorting is based on field and direction, multiple sorting options can be provided.
+  /// Sorting is based on field and direction, multiple sorting options can be
-  /// You can sort based on last_updated, last_message_at, updated_at, created_at or member_count.
+  /// provided.
-  /// Direction can be ascending or descending.
+  /// You can sort based on last_updated, last_message_at, updated_at, created_
+  /// at or member_count. Direction can be ascending or descending.
   final List<SortOption> sortOptions;
 
   /// Pagination parameters
@@ -103,10 +109,9 @@ class MessageSearchListCore extends StatefulWidget {
 
 class _MessageSearchListCoreState extends State<MessageSearchListCore> {
   @override
-  void initState() {
+  void didChangeDependencies() {
-    super.initState();
+    super.didChangeDependencies();
-    final messageSearchBloc = MessageSearchBloc.of(context);
+    MessageSearchBloc.of(context).search(
-    messageSearchBloc.search(
       filter: widget.filters,
       sort: widget.sortOptions,
       query: widget.messageQuery,
@@ -126,37 +131,34 @@ class _MessageSearchListCoreState extends State<MessageSearchListCore> {
     return _buildListView(messageSearchBloc);
   }
 
-  Widget _buildListView(MessageSearchBlocState messageSearchBloc) {
+  Widget _buildListView(MessageSearchBlocState messageSearchBloc) =>
-    return StreamBuilder<List<GetMessageResponse>>(
+      StreamBuilder<List<GetMessageResponse>>(
-      stream: messageSearchBloc.messagesStream,
+        stream: messageSearchBloc.messagesStream,
-      builder: (context, snapshot) {
+        builder: (context, snapshot) {
-        if (snapshot.hasError) {
+          if (snapshot.hasError) {
-          if (snapshot.error is Error) {
+            if (snapshot.error is Error) {
-            print((snapshot.error as Error).stackTrace);
+              print((snapshot.error as Error).stackTrace);
+            }
+
+            return widget.errorBuilder(context, snapshot.error);
           }
 
-          return widget.errorBuilder(context, snapshot.error);
+          if (!snapshot.hasData) {
-        }
+            return widget.loadingBuilder(context);
+          }
 
-        if (!snapshot.hasData) {
+          final items = snapshot.data;
-          return widget.loadingBuilder(context);
-        }
 
-        final items = snapshot.data;
+          if (items.isEmpty) {
+            return widget.emptyBuilder(context);
+          }
 
-        if (items.isEmpty) {
+          return widget.childBuilder(snapshot.data);
-          return widget.emptyBuilder(context);
+        },
-        }
+      );
-
-        return widget.childBuilder(snapshot.data);
-      },
-    );
-  }
 
   void loadData() {
-    final messageSearchBloc = MessageSearchBloc.of(context);
+    MessageSearchBloc.of(context).search(
-
-    messageSearchBloc.search(
       filter: widget.filters,
       sort: widget.sortOptions,
       query: widget.messageQuery,
@@ -189,8 +191,7 @@ class _MessageSearchListCoreState extends State<MessageSearchListCore> {
         widget.messageQuery?.toString() != oldWidget.messageQuery?.toString() ||
         widget.messageFilters?.toString() !=
             oldWidget.messageFilters?.toString()) {
-      final messageSearchBloc = MessageSearchBloc.of(context);
+      MessageSearchBloc.of(context).search(
-      messageSearchBloc.search(
         filter: widget.filters,
         sort: widget.sortOptions,
         query: widget.messageQuery,

packages/stream_chat_flutter_core/lib/src/stream_channel.dart

@@ -1,5 +1,6 @@
 import 'dart:async';
 
+import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:rxdart/rxdart.dart';
 import 'package:stream_chat/stream_chat.dart';
@@ -25,8 +26,8 @@ class StreamChannel extends StatefulWidget {
     @required this.channel,
     this.showLoading = true,
     this.initialMessageId,
-  })  : assert(child != null),
+  })  : assert(child != null, 'Child should not be null'),
-        assert(channel != null),
+        assert(channel != null, 'Channel should not be null'),
         super(key: key);
 
   // ignore: public_member_api_docs
@@ -49,7 +50,8 @@ class StreamChannel extends StatefulWidget {
 
     if (streamChannelState == null) {
       throw Exception(
-          'You must have a StreamChannel widget at the top of your widget tree');
+        'You must have a StreamChannel widget at the top of your widget tree',
+      );
     }
 
     return streamChannelState;
@@ -204,14 +206,13 @@ class StreamChannelState extends State<StreamChannel> {
     int before = 20,
     int after = 20,
     bool preferOffline = false,
-  }) {
+  }) =>
-    return queryAtMessage(
+      queryAtMessage(
-      messageId: messageId,
+        messageId: messageId,
-      before: before,
+        before: before,
-      after: after,
+        after: after,
-      preferOffline: preferOffline,
+        preferOffline: preferOffline,
-    );
+      );
-  }
 
   ///
   Future<void> queryAtMessage({
@@ -254,15 +255,14 @@ class StreamChannelState extends State<StreamChannel> {
     String messageId, {
     int limit = 20,
     bool preferOffline = false,
-  }) {
+  }) =>
-    return channel.query(
+      channel.query(
-      messagesPagination: PaginationParams(
+        messagesPagination: PaginationParams(
-        lessThan: messageId,
+          lessThan: messageId,
-        limit: limit,
+          limit: limit,
-      ),
+        ),
-      preferOffline: preferOffline,
+        preferOffline: preferOffline,
-    );
+      );
-  }
 
   ///
   Future<ChannelState> queryAfterMessage(
@@ -366,9 +366,10 @@ class StreamChannelState extends State<StreamChannel> {
           );
         }
         final initialized = snapshot.data[0];
+        // ignore: avoid_bool_literals_in_conditional_expressions
         final dataLoaded = initialMessageId == null ? true : snapshot.data[1];
         if (widget.showLoading && (!initialized || !dataLoaded)) {
-          return Center(
+          return const Center(
             child: CircularProgressIndicator(),
           );
         }

packages/stream_chat_flutter_core/lib/src/stream_chat_core.dart

@@ -3,13 +3,12 @@ import 'dart:async';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:stream_chat/stream_chat.dart';
-
+import 'package:stream_chat_flutter_core/src/typedef.dart';
-import 'typedef.dart';
 
 /// Widget used to provide information about the chat to the widget tree.
 /// This Widget is used to react to life cycle changes and system updates.
-/// When the app goes into the background, the websocket connection is kept alive
+/// When the app goes into the background, the websocket connection is kept
-/// for two minutes before being terminated.
+/// alive for two minutes before being terminated.
 ///
 /// Conversely, when app is resumed or restarted, a new connection is initiated.
 ///
@@ -36,16 +35,16 @@ import 'typedef.dart';
 class StreamChatCore extends StatefulWidget {
   /// Constructor used for creating a new instance of [StreamChatCore].
   ///
-  /// [StreamChatCore] is a stateful widget which reacts to system events and updates
+  /// [StreamChatCore] is a stateful widget which reacts to system events and
-  /// Stream's connection status accordingly.
+  /// updates Stream's connection status accordingly.
-  StreamChatCore({
+  const StreamChatCore({
     Key key,
     @required this.client,
     @required this.child,
     this.onBackgroundEventReceived,
     this.backgroundKeepAlive = const Duration(minutes: 1),
-  })  : assert(client != null),
+  })  : assert(client != null, 'Stream Chat Client should not be null'),
-        assert(child != null),
+        assert(child != null, 'Child should not be null'),
         super(key: key);
 
   /// Instance of Stream Chat Client containing information about the current
@@ -55,7 +54,8 @@ class StreamChatCore extends StatefulWidget {
   /// Widget descendant.
   final Widget child;
 
-  /// The amount of time that will pass before disconnecting the client in the background
+  /// The amount of time that will pass before disconnecting the client in
+  /// the background
   final Duration backgroundKeepAlive;
 
   /// Handler called whenever the [client] receives a new [Event] while the app
@@ -90,9 +90,7 @@ class StreamChatCoreState extends State<StreamChatCore>
   Timer _disconnectTimer;
 
   @override
-  Widget build(BuildContext context) {
+  Widget build(BuildContext context) => widget.child;
-    return widget.child;
-  }
 
   /// The current user
   User get user => widget.client.state.user;

packages/stream_chat_flutter_core/lib/src/typedef.dart

@@ -2,8 +2,8 @@ import 'package:flutter/widgets.dart';
 import 'package:stream_chat/stream_chat.dart';
 
 /// A signature for a callback which exposes an error and returns a function.
-/// This Callback can be used in cases where an API failure occurs and the widget
+/// This Callback can be used in cases where an API failure occurs and the
-/// is unable to render data.
+/// widget is unable to render data.
 typedef ErrorBuilder = Widget Function(BuildContext context, Object error);
 
 /// A Signature for a handler function which will expose a [event].

packages/stream_chat_flutter_core/lib/src/user_list_core.dart

@@ -1,11 +1,13 @@
 import 'dart:convert';
 
+import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:stream_chat/stream_chat.dart';
 import 'package:stream_chat_flutter_core/src/users_bloc.dart';
 
 ///
-/// [UserListCore] is a simplified class that allows fetching users while exposing UI builders.
+/// [UserListCore] is a simplified class that allows fetching users while
+/// exposing UI builders.
 /// A [UserListController] is used to load and paginate data.
 ///
 /// ```dart
@@ -50,30 +52,31 @@ import 'package:stream_chat_flutter_core/src/users_bloc.dart';
 /// [UsersBloc] must be the ancestor of this widget. This is necessary since
 /// [UserListCore] depends on functionality contained within [UsersBloc].
 ///
-/// The parameters [listBuilder], [loadingBuilder], [emptyBuilder] and [errorBuilder] must all be supplied
+/// The parameters [listBuilder], [loadingBuilder], [emptyBuilder] and
-/// and not null.
+/// [errorBuilder] must all be supplied and not null.
 class UserListCore extends StatefulWidget {
   /// Instantiate a new [UserListCore]
   const UserListCore({
-    Key key,
     @required this.errorBuilder,
     @required this.emptyBuilder,
     @required this.loadingBuilder,
     @required this.listBuilder,
+    Key key,
     this.filter,
     this.options,
     this.sort,
     this.pagination,
     this.groupAlphabetically = false,
     this.userListController,
-  })  : assert(errorBuilder != null),
+  })  : assert(errorBuilder != null, ''),
-        assert(emptyBuilder != null),
+        assert(emptyBuilder != null, ''),
-        assert(loadingBuilder != null),
+        assert(loadingBuilder != null, ''),
-        assert(listBuilder != null),
+        assert(listBuilder != null, ''),
         super(key: key);
 
   /// A [UserListController] allows reloading and pagination.
-  /// Use [UserListController.loadData] and [UserListController.paginateData] respectively for reloading and pagination.
+  /// Use [UserListController.loadData] and [UserListController.paginateData]
+  /// respectively for reloading and pagination.
   final UserListController userListController;
 
   /// The builder that will be used in case of error
@@ -100,9 +103,9 @@ class UserListCore extends StatefulWidget {
   final Map<String, dynamic> options;
 
   /// The sorting used for the channels matching the filters.
-  /// Sorting is based on field and direction, multiple sorting options can be provided.
+  /// Sorting is based on field and direction, multiple sorting options can be
-  /// You can sort based on last_updated, last_message_at, updated_at, created_at or member_count.
+  /// provided. You can sort based on last_updated, last_message_at, updated_at,
-  /// Direction can be ascending or descending.
+  /// created_at or member_count. Direction can be ascending or descending.
   final List<SortOption> sort;
 
   /// Pagination parameters
@@ -123,10 +126,9 @@ class UserListCore extends StatefulWidget {
 class _UserListCoreState extends State<UserListCore>
     with WidgetsBindingObserver {
   @override
-  void initState() {
+  void didChangeDependencies() {
-    super.initState();
+    super.didChangeDependencies();
-    final usersBloc = UsersBloc.of(context);
+    UsersBloc.of(context).queryUsers(
-    usersBloc.queryUsers(
       filter: widget.filter,
       sort: widget.sort,
       pagination: widget.pagination,
@@ -151,68 +153,66 @@ class _UserListCoreState extends State<UserListCore>
 
   Stream<List<ListItem>> _buildUserStream(
     UsersBlocState usersBlocState,
-  ) {
+  ) =>
-    return usersBlocState.usersStream.map(
+      usersBlocState.usersStream.map(
-      (users) {
+        (users) {
-        if (widget.groupAlphabetically) {
+          if (widget.groupAlphabetically) {
-          var temp = users;
+            var temp = users;
-          if (!isListAlreadySorted) {
+            if (!isListAlreadySorted) {
-            temp = users..sort((curr, next) => curr.name.compareTo(next.name));
+              temp = users
+                ..sort((curr, next) => curr.name.compareTo(next.name));
+            }
+            final groupedUsers = <String, List<User>>{};
+            for (final e in temp) {
+              final alphabet = e.name[0]?.toUpperCase();
+              groupedUsers[alphabet] = [...groupedUsers[alphabet] ?? [], e];
+            }
+            final items = <ListItem>[];
+            for (final key in groupedUsers.keys) {
+              items
+                ..add(ListHeaderItem(key))
+                ..addAll(groupedUsers[key].map((e) => ListUserItem(e)));
+            }
+            return items;
           }
-          final groupedUsers = <String, List<User>>{};
+          return users.map((e) => ListUserItem(e)).toList();
-          for (final e in temp) {
+        },
-            final alphabet = e.name[0]?.toUpperCase();
+      );
-            groupedUsers[alphabet] = [...groupedUsers[alphabet] ?? [], e];
-          }
-          final items = <ListItem>[];
-          for (final key in groupedUsers.keys) {
-            items.add(ListHeaderItem(key));
-            items.addAll(groupedUsers[key].map((e) => ListUserItem(e)));
-          }
-          return items;
-        }
-        return users.map((e) => ListUserItem(e)).toList();
-      },
-    );
-  }
 
   StreamBuilder<List<ListItem>> _buildListView(
     UsersBlocState usersBlocState,
-  ) {
+  ) =>
-    return StreamBuilder(
+      StreamBuilder(
-      stream: _buildUserStream(usersBlocState),
+        stream: _buildUserStream(usersBlocState),
-      builder: (context, snapshot) {
+        builder: (context, snapshot) {
-        if (snapshot.hasError) {
+          if (snapshot.hasError) {
-          if (snapshot.error is Error) {
+            if (snapshot.error is Error) {
-            print((snapshot.error as Error).stackTrace);
+              print((snapshot.error as Error).stackTrace);
+            }
+
+            return widget.errorBuilder(snapshot.error);
           }
 
-          return widget.errorBuilder(snapshot.error);
+          if (!snapshot.hasData) {
-        }
+            return widget.loadingBuilder(context);
+          }
 
-        if (!snapshot.hasData) {
+          final items = snapshot.data;
-          return widget.loadingBuilder(context);
-        }
 
-        final items = snapshot.data;
+          if (items.isEmpty) {
+            return widget.emptyBuilder(context);
+          }
 
-        if (items.isEmpty) {
+          if (items.isEmpty) {
-          return widget.emptyBuilder(context);
+            return widget.emptyBuilder(context);
-        }
+          }
 
-        if (items.isEmpty) {
+          return widget.listBuilder(context, items);
-          return widget.emptyBuilder(context);
+        },
-        }
+      );
-
-        return widget.listBuilder(context, items);
-      },
-    );
-  }
 
   void loadData() {
-    final _usersBloc = UsersBloc.of(context);
+    UsersBloc.of(context).queryUsers(
-
-    _usersBloc.queryUsers(
       filter: widget.filter,
       sort: widget.sort,
       pagination: widget.pagination,
@@ -241,8 +241,7 @@ class _UserListCoreState extends State<UserListCore>
         widget.pagination?.toJson()?.toString() !=
             oldWidget.pagination?.toJson()?.toString() ||
         widget.options?.toString() != oldWidget.options?.toString()) {
-      final usersBloc = UsersBloc.of(context);
+      UsersBloc.of(context).queryUsers(
-      usersBloc.queryUsers(
         filter: widget.filter,
         sort: widget.sort,
         pagination: widget.pagination,
@@ -253,8 +252,8 @@ class _UserListCoreState extends State<UserListCore>
 }
 
 /// Represents an item in a the user stream list.
-/// Header items are prefixed with the key `HEADER` While users are prefixed with
+/// Header items are prefixed with the key `HEADER` While users are prefixed
-/// `USER`.
+/// with `USER`.
 abstract class ListItem {
   // ignore: public_member_api_docs
   String get key {
@@ -280,26 +279,26 @@ abstract class ListItem {
     if (this is ListUserItem) {
       return userItem((this as ListUserItem).user);
     }
-    return SizedBox();
+    return const SizedBox();
   }
 }
 
 // ignore: public_member_api_docs
 class ListHeaderItem extends ListItem {
   // ignore: public_member_api_docs
-  final String heading;
+  ListHeaderItem(this.heading);
 
   // ignore: public_member_api_docs
-  ListHeaderItem(this.heading);
+  final String heading;
 }
 
 // ignore: public_member_api_docs
 class ListUserItem extends ListItem {
   // ignore: public_member_api_docs
-  final User user;
+  ListUserItem(this.user);
 
   // ignore: public_member_api_docs
-  ListUserItem(this.user);
+  final User user;
 }
 
 /// Controller used for paginating data in [ChannelListView]

packages/stream_chat_flutter_core/lib/src/users_bloc.dart

@@ -1,8 +1,8 @@
+import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:rxdart/rxdart.dart';
 import 'package:stream_chat/stream_chat.dart';
-
+import 'package:stream_chat_flutter_core/stream_chat_flutter_core.dart';
-import 'stream_chat_core.dart';
 
 /// Widget dedicated to the management of a users list with pagination.
 ///
@@ -14,9 +14,12 @@ class UsersBloc extends StatefulWidget {
   /// Instantiate a new [UsersBloc]. The parameter [child] must be supplied and
   /// not null.
   const UsersBloc({
-    Key key,
     @required this.child,
-  })  : assert(child != null),
+    Key key,
+  })  : assert(
+            child != null,
+            'When constructing a UsersBloc, the parameter '
+            'child should not be null.'),
         super(key: key);
 
   /// The widget child

packages/stream_chat_flutter_core/lib/stream_chat_flutter_core.dart

@@ -1,5 +1,7 @@
 library stream_chat_flutter_core;
 
+export 'package:stream_chat/stream_chat.dart';
+
 export 'src/channel_list_core.dart';
 export 'src/channels_bloc.dart';
 export 'src/lazy_load_scroll_view.dart';
@@ -8,7 +10,6 @@ export 'src/message_search_bloc.dart';
 export 'src/message_search_list_core.dart';
 export 'src/stream_channel.dart';
 export 'src/stream_chat_core.dart';
+export 'src/typedef.dart';
 export 'src/user_list_core.dart';
 export 'src/users_bloc.dart';
-export 'src/typedef.dart';
-export 'package:stream_chat/stream_chat.dart';

packages/stream_chat_flutter_core/pubspec.yaml

@@ -10,14 +10,13 @@ environment:
   flutter: ">=1.17.0"
 
 dependencies:
-  stream_chat: ^1.5.0
   flutter:
     sdk: flutter
   rxdart: ^0.25.0
+  stream_chat: ^1.5.0
 
 dev_dependencies:
-  mockito: ^4.1.4
+  fake_async: ^1.1.0
   flutter_test:
     sdk: flutter
-  fake_async: ^1.1.0
+  mockito: ^4.1.4
-  

packages/stream_chat_flutter_core/test/stream_chat_core_test.dart

@@ -3,8 +3,8 @@ import 'dart:async';
 import 'package:fake_async/fake_async.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
-import 'package:stream_chat_flutter_core/stream_chat_flutter_core.dart';
 import 'package:mockito/mockito.dart';
+import 'package:stream_chat_flutter_core/stream_chat_flutter_core.dart';
 
 import 'mocks.dart';
 
@@ -110,17 +110,14 @@ void main() {
             onBackgroundEventReceived: showLocalNotificationMock,
             backgroundKeepAlive: const Duration(seconds: 4),
             child: Builder(
-              builder: (context) {
+              builder: (context) => Container(),
-                return Container();
-              },
             ),
           ),
         );
 
-        final sc = scKey.currentState;
+        scKey.currentState.didChangeAppLifecycleState(AppLifecycleState.paused);
-        sc.didChangeAppLifecycleState(AppLifecycleState.paused);
 
-        _async.elapse(Duration(seconds: 5));
+        _async.elapse(const Duration(seconds: 5));
 
         verify(client.disconnect()).called(1);
         eventStreamController.close();
@@ -129,7 +126,8 @@ void main() {
   );
 
   testWidgets(
-    'StreamChatCore should handle notifications when on background and connected',
+    'StreamChatCore should handle notifications when on background and '
+    'connected',
     (WidgetTester tester) async {
       final client = MockClient();
       final clientState = MockClientState();
@@ -154,15 +152,12 @@ void main() {
           onBackgroundEventReceived: showLocalNotificationMock,
           backgroundKeepAlive: const Duration(seconds: 4),
           child: Builder(
-            builder: (context) {
+            builder: (context) => Container(),
-              return Container();
-            },
           ),
         ),
       );
 
-      final sc = scKey.currentState;
+      scKey.currentState.didChangeAppLifecycleState(AppLifecycleState.paused);
-      sc.didChangeAppLifecycleState(AppLifecycleState.paused);
       final event = Event(
         type: EventType.messageNew,
         message: Message(text: 'hey'),