Apply some common linter rules

analysis_options.yaml

@@ -0,0 +1,157 @@
+analyzer:
+  strong-mode:
+    implicit-dynamic: false
+  errors:
+    # treat missing required parameters as a warning (not a hint)
+    missing_required_param: warning
+    # treat missing returns as a warning (not a hint)
+    missing_return: warning
+    # allow having TODOs in the code
+    todo: ignore
+    # Ignore analyzer hints for updating pubspecs when using Future or
+    # Stream and not importing dart:async
+    # Please see https://github.com/flutter/flutter/pull/24528 for details.
+    sdk_version_async_exported_from_core: ignore
+  exclude:
+    - 'bin/cache/**'
+    # the following two are relative to the stocks example and the flutter package respectively
+    # see https://github.com/dart-lang/sdk/issues/28463
+    - 'lib/i18n/stock_messages_*.dart'
+    - 'lib/src/http/**'
+
+linter:
+  rules:
+    # these rules are documented on and in the same order as
+    # the Dart Lint rules page to make maintenance easier
+    # https://github.com/dart-lang/linter/blob/master/example/all.yaml
+    - always_declare_return_types
+    - always_put_control_body_on_new_line
+    # - always_put_required_named_parameters_first # we prefer having parameters in the same order as fields https://github.com/flutter/flutter/issues/10219
+    - always_require_non_null_named_parameters
+    - annotate_overrides
+    # - avoid_annotating_with_dynamic # conflicts with always_specify_types
+    - avoid_as
+    # - avoid_bool_literals_in_conditional_expressions # not yet tested
+    # - avoid_catches_without_on_clauses # we do this commonly
+    # - avoid_catching_errors # we do this commonly
+    - avoid_classes_with_only_static_members
+    # - avoid_double_and_int_checks # only useful when targeting JS runtime
+    - avoid_empty_else
+    - avoid_field_initializers_in_const_classes
+    - avoid_function_literals_in_foreach_calls
+    # - avoid_implementing_value_types # not yet tested
+    - avoid_init_to_null
+    # - avoid_js_rounded_ints # only useful when targeting JS runtime
+    - avoid_null_checks_in_equality_operators
+    # - avoid_positional_boolean_parameters # not yet tested
+    # - avoid_private_typedef_functions # we prefer having typedef (discussion in https://github.com/flutter/flutter/pull/16356)
+    - avoid_relative_lib_imports
+    - avoid_renaming_method_parameters
+    - avoid_return_types_on_setters
+    # - avoid_returning_null # there are plenty of valid reasons to return null
+    # - avoid_returning_null_for_future # not yet tested
+    - avoid_returning_null_for_void
+    # - avoid_returning_this # there are plenty of valid reasons to return this
+    # - avoid_setters_without_getters # not yet tested
+    # - avoid_shadowing_type_parameters # not yet tested
+    # - avoid_single_cascade_in_expression_statements # not yet tested
+    - avoid_slow_async_io
+    - avoid_types_as_parameter_names
+    # - avoid_types_on_closure_parameters # conflicts with always_specify_types
+    - avoid_unused_constructor_parameters
+    - avoid_void_async
+    - await_only_futures
+    - camel_case_types
+    - cancel_subscriptions
+    # - cascade_invocations # not yet tested
+    # - close_sinks # not reliable enough
+    # - comment_references # blocked on https://github.com/flutter/flutter/issues/20765
+    # - constant_identifier_names # needs an opt-out https://github.com/dart-lang/linter/issues/204
+    - control_flow_in_finally
+    # - curly_braces_in_flow_control_structures # not yet tested
+    - directives_ordering
+    - empty_catches
+    - empty_constructor_bodies
+    - empty_statements
+    # - file_names # not yet tested
+    - flutter_style_todos
+    - hash_and_equals
+    - implementation_imports
+    # - invariant_booleans # too many false positives: https://github.com/dart-lang/linter/issues/811
+    - iterable_contains_unrelated_type
+    # - join_return_with_assignment # not yet tested
+    - library_names
+    - library_prefixes
+    # - lines_longer_than_80_chars # not yet tested
+    - list_remove_unrelated_type
+    # - literal_only_boolean_expressions # too many false positives: https://github.com/dart-lang/sdk/issues/34181
+    - no_adjacent_strings_in_list
+    - no_duplicate_case_values
+    - non_constant_identifier_names
+    # - null_closures  # not yet tested
+    # - omit_local_variable_types # opposite of always_specify_types
+    # - one_member_abstracts # too many false positives
+    # - only_throw_errors # https://github.com/flutter/flutter/issues/5792
+    - overridden_fields
+    - package_api_docs
+    - package_names
+    - package_prefixed_library_names
+    # - parameter_assignments # we do this commonly
+    - prefer_adjacent_string_concatenation
+    - prefer_asserts_in_initializer_lists
+    - 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 # not yet tested
+    - prefer_contains
+    - prefer_equal_for_default_values
+    # - prefer_expression_function_bodies # conflicts with https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo#consider-using--for-short-functions-and-methods
+    - prefer_final_fields
+    - prefer_final_locals
+    - prefer_foreach
+    # - prefer_function_declarations_over_variables # not yet tested
+    - prefer_generic_function_type_aliases
+    - prefer_initializing_formals
+    # - prefer_int_literals # not yet tested
+    # - prefer_interpolation_to_compose_strings # not yet tested
+    - prefer_is_empty
+    - prefer_is_not_empty
+    - prefer_iterable_whereType
+    # - prefer_mixin # https://github.com/dart-lang/language/issues/32
+    # - prefer_null_aware_operators # disable until NNBD, see https://github.com/flutter/flutter/pull/32711#issuecomment-492930932
+    - prefer_single_quotes
+    - prefer_typing_uninitialized_variables
+    - prefer_void_to_null
+    # - public_member_api_docs # enabled on a case-by-case basis; see e.g. packages/analysis_options.yaml
+    - recursive_getters
+    - slash_for_doc_comments
+    - sort_pub_dependencies
+    # - super_goes_last # no longer needed w/ Dart 2
+    - test_types_in_equals
+    - throw_in_finally
+    # - type_annotate_public_apis # subset of always_specify_types
+    - type_init_formals
+    # - unawaited_futures # too many false positives
+    # - unnecessary_await_in_return # not yet tested
+    - unnecessary_brace_in_string_interps
+    - unnecessary_const
+    - unnecessary_getters_setters
+    # - unnecessary_lambdas # has false positives: https://github.com/dart-lang/linter/issues/498
+    - unnecessary_new
+    - unnecessary_null_aware_assignments
+    - unnecessary_null_in_if_null_operators
+    - unnecessary_overrides
+    - unnecessary_parenthesis
+    - unnecessary_statements
+    - unnecessary_this
+    - unrelated_type_equality_checks
+    # - use_function_type_syntax_for_parameters # not yet tested
+    - use_rethrow_when_possible
+    # - use_setters_to_change_properties # not yet tested
+    # - use_string_buffers # has false positives: https://github.com/dart-lang/sdk/issues/34182
+    # - use_to_and_as_if_applicable # has false positives, so we prefer to catch this by code-review
+    - valid_regexps
+    # - void_checks # not yet tested

lib/fl_chart_widget.dart

@@ -27,7 +27,7 @@ class FlChartWidget extends StatefulWidget {
     @required this.flChart,
   }) : super(key: key) {
     if (flChart == null) {
-      throw Exception("flChart might not be null");
+      throw Exception('flChart might not be null');
     }
   }
 

lib/src/chart/bar_chart/bar_chart_data.dart

@@ -44,12 +44,12 @@ class BarChartData extends FlAxisChartData {
     double maxY,
   ) {
     barGroups.forEach((barData) {
-      if (barData.barRods == null || barData.barRods.length <= 0) {
-        throw Exception("barRods could not be null or empty");
+      if (barData.barRods == null || barData.barRods.isEmpty) {
+        throw Exception('barRods could not be null or empty');
       }
     });
 
-    if (barGroups.length > 0) {
+    if (barGroups.isNotEmpty) {
       var canModifyMinX = false;
       if (minX == null) {
         minX = barGroups[0].x.toDouble();
@@ -150,7 +150,7 @@ class BarChartGroupData {
   /// calculates the whole width of our group,
   /// by adding all rod's width and group space * rods count.
   double get width {
-    if (barRods.length == 0) {
+    if (barRods.isEmpty) {
       return 0;
     }
 

lib/src/chart/bar_chart/bar_chart_painter.dart

@@ -16,16 +16,16 @@ class BarChartPainter extends FlAxisChartPainter {
   }
 
   @override
-  void paint(Canvas canvas, Size viewSize) {
-    super.paint(canvas, viewSize);
+  void paint(Canvas canvas, Size size) {
+    super.paint(canvas, size);
 
-    if (data.barGroups.length == 0) {
+    if (data.barGroups.isEmpty) {
       return;
     }
 
-    List<double> groupsX = calculateGroupsX(viewSize, data.barGroups, data.alignment);
-    drawBars(canvas, viewSize, groupsX);
-    drawTitles(canvas, viewSize, groupsX);
+    List<double> groupsX = calculateGroupsX(size, data.barGroups, data.alignment);
+    drawBars(canvas, size, groupsX);
+    drawTitles(canvas, size, groupsX);
   }
 
   /// this method calculates the x of our showing groups,
@@ -199,13 +199,13 @@ class BarChartPainter extends FlAxisChartPainter {
         String text =
             data.titlesData.getVerticalTitles(data.gridData.verticalInterval * verticalCounter);
 
-        TextSpan span = new TextSpan(style: data.titlesData.verticalTitlesTextStyle, text: text);
-        TextPainter tp = new TextPainter(
+        TextSpan span = TextSpan(style: data.titlesData.verticalTitlesTextStyle, text: text);
+        TextPainter tp = TextPainter(
             text: span, textAlign: TextAlign.center, textDirection: TextDirection.ltr);
         tp.layout(maxWidth: getExtraNeededHorizontalSpace());
         x -= tp.width + data.titlesData.verticalTitleMargin;
         y -= (tp.height / 2);
-        tp.paint(canvas, new Offset(x, y));
+        tp.paint(canvas, Offset(x, y));
 
         verticalCounter++;
       }
@@ -215,8 +215,8 @@ class BarChartPainter extends FlAxisChartPainter {
     groupsX.asMap().forEach((int index, double x) {
       String text = data.titlesData.getHorizontalTitles(index.toDouble());
 
-      TextSpan span = new TextSpan(style: data.titlesData.horizontalTitlesTextStyle, text: text);
-      TextPainter tp = new TextPainter(
+      TextSpan span = TextSpan(style: data.titlesData.horizontalTitlesTextStyle, text: text);
+      TextPainter tp = TextPainter(
           text: span, textAlign: TextAlign.center, textDirection: TextDirection.ltr);
       tp.layout();
 
@@ -259,6 +259,7 @@ class BarChartPainter extends FlAxisChartPainter {
   /// calculate left offset for draw the chart,
   /// maybe we want to show both left and right titles,
   /// then just the left titles will effect on this function.
+  @override
   double getLeftOffsetDrawSize() {
     double parentNeeded = super.getLeftOffsetDrawSize();
     if (data.titlesData.show && data.titlesData.showVerticalTitles) {

lib/src/chart/base/fl_axis_chart/fl_axis_chart_painter.dart

@@ -12,13 +12,13 @@ abstract class FlAxisChartPainter<D extends FlAxisChartData> extends FlChartPain
   Paint gridPaint;
 
   FlAxisChartPainter(this.data) : super(data) {
-    gridPaint = new Paint()..style = PaintingStyle.fill;
+    gridPaint = Paint()..style = PaintingStyle.fill;
   }
 
   @override
-  void paint(Canvas canvas, Size viewSize) {
-    super.paint(canvas, viewSize);
-    drawGrid(canvas, viewSize);
+  void paint(Canvas canvas, Size size) {
+    super.paint(canvas, size);
+    drawGrid(canvas, size);
   }
 
   void drawGrid(Canvas canvas, Size viewSize) {

lib/src/chart/base/fl_chart/fl_chart_data.dart

@@ -11,9 +11,7 @@ class FlChartData {
   FlChartData({
     this.borderData,
   }) {
-    if (borderData == null) {
-      borderData = FlBorderData();
-    }
+    borderData ??= FlBorderData();
   }
 }
 
@@ -28,13 +26,11 @@ class FlBorderData {
     this.show = true,
     this.border,
   }) {
-    if (border == null) {
-      border = Border.all(
+    border ??= Border.all(
         color: Colors.black,
         width: 1.0,
         style: BorderStyle.solid,
       );
-    }
   }
 }
 
@@ -46,7 +42,7 @@ class FlBorderData {
 typedef GetTitleFunction = String Function(double value);
 
 String defaultGetTitle(double value) {
-  return "${value.toInt()}";
+  return '${value.toInt()}';
 }
 
 /// This class is responsible to hold data about showing titles.

lib/src/chart/base/fl_chart/fl_chart_painter.dart

@@ -21,8 +21,8 @@ abstract class FlChartPainter<D extends FlChartData> extends CustomPainter {
   }
 
   @override
-  void paint(Canvas canvas, Size viewSize) {
-    drawViewBorder(canvas, viewSize);
+  void paint(Canvas canvas, Size size) {
+    drawViewBorder(canvas, size);
   }
 
   void drawViewBorder(Canvas canvas, Size viewSize) {

lib/src/chart/line_chart/line_chart_data.dart

@@ -35,11 +35,11 @@ class LineChartData extends FlAxisChartData {
     double maxY,
   ) {
     lineBarsData.forEach((lineBarChart) {
-      if (lineBarChart.spots == null || lineBarChart.spots.length <= 0) {
-        throw Exception("spots could not be null or empty");
+      if (lineBarChart.spots == null || lineBarChart.spots.isEmpty) {
+        throw Exception('spots could not be null or empty');
       }
     });
-    if (lineBarsData.length > 0) {
+    if (lineBarsData.isNotEmpty) {
       var canModifyMinX = false;
       if (minX == null) {
         minX = lineBarsData[0].spots[0].x;

lib/src/chart/line_chart/line_chart_painter.dart

@@ -30,7 +30,7 @@ class LineChartPainter extends FlAxisChartPainter {
   @override
   void paint(Canvas canvas, Size viewSize) {
     super.paint(canvas, viewSize);
-    if (data.lineBarsData.length == 0) {
+    if (data.lineBarsData.isEmpty) {
       return;
     }
 
@@ -245,13 +245,13 @@ class LineChartPainter extends FlAxisChartPainter {
         String text =
             data.titlesData.getVerticalTitles(data.gridData.verticalInterval * verticalCounter);
 
-        TextSpan span = new TextSpan(style: data.titlesData.verticalTitlesTextStyle, text: text);
-        TextPainter tp = new TextPainter(
+        TextSpan span = TextSpan(style: data.titlesData.verticalTitlesTextStyle, text: text);
+        TextPainter tp = TextPainter(
             text: span, textAlign: TextAlign.center, textDirection: TextDirection.ltr);
         tp.layout(maxWidth: getExtraNeededHorizontalSpace());
         x -= tp.width + data.titlesData.verticalTitleMargin;
         y -= (tp.height / 2);
-        tp.paint(canvas, new Offset(x, y));
+        tp.paint(canvas, Offset(x, y));
 
         verticalCounter++;
       }
@@ -267,8 +267,8 @@ class LineChartPainter extends FlAxisChartPainter {
         String text = data.titlesData
             .getHorizontalTitles(data.gridData.horizontalInterval * horizontalCounter);
 
-        TextSpan span = new TextSpan(style: data.titlesData.horizontalTitlesTextStyle, text: text);
-        TextPainter tp = new TextPainter(
+        TextSpan span = TextSpan(style: data.titlesData.horizontalTitlesTextStyle, text: text);
+        TextPainter tp = TextPainter(
             text: span, textAlign: TextAlign.center, textDirection: TextDirection.ltr);
         tp.layout();
 
@@ -313,6 +313,7 @@ class LineChartPainter extends FlAxisChartPainter {
   /// calculate left offset for draw the chart,
   /// maybe we want to show both left and right titles,
   /// then just the left titles will effect on this function.
+  @override
   double getLeftOffsetDrawSize() {
     double parentNeeded = super.getLeftOffsetDrawSize();
     if (data.titlesData.show && data.titlesData.showVerticalTitles) {

lib/src/chart/pie_chart/pie_chart_data.dart

@@ -68,7 +68,7 @@ class PieChartSectionData {
     this.showTitle = true,
     this.titleStyle =
         const TextStyle(color: Colors.white, fontSize: 16, fontWeight: FontWeight.bold),
-    this.title = "1",
+    this.title = '1',
     this.titlePositionPercentageOffset = 0.5,
   });
 }