pyramid_lint 0.6.0

pyramid_lint introduces a set of additional lints and fixes to enforce a consistent coding style, prevent common mistakes and enhance code readability.

Pyramid Lint

pyramid_lint introduces a set of additional lints and fixes to enforce a consistent coding style, prevent common mistakes and enhance code readability using custom_lint.

Table of contents

• Table of contents
• Installation
• Configuration
• Dart lints
  • avoid_duplicate_import
  • avoid_dynamic
  • avoid_empty_block
  • avoid_inverted_boolean_expression
  • max_lines_for_file
  • max_lines_for_function
  • prefer_declaring_const_constructor
  • prefer_declaring_parameter_name
  • prefer_immediate_return
  • prefer_iterable_first
  • prefer_iterable_last
  • prefer_underscore_for_unused_callback_parameters
• Flutter lints
  • avoid_single_child_in_flex
  • correct_order_for_super_dispose
  • correct_order_for_super_init_state
  • prefer_async_callback
  • prefer_border_from_border_side
  • prefer_border_radius_all
  • prefer_dedicated_media_query_method
  • prefer_spacer
  • prefer_text_rich
  • proper_controller_dispose
  • proper_edge_insets_constructor
  • proper_usage_of_expanded_and_flexible
  • proper_usage_of_from_environment
• Dart assists
  • invert_boolean_expression
  • swap_then_else_expression
• Flutter assists
  • use_edge_insets_zero
  • wrap_with_expanded
  • wrap_with_layout_builder
  • wrap_with_stack

Installation

Run the following command to add custom_lint and pyramid_lint to your project's dev dependencies:

dart pub add --dev custom_lint pyramid_lint

Enable custom_lint in your analysis_options.yaml file:

analyzer:
  plugins:
    - custom_lint

Configuration

By default, all lints are enabled. To disable a specific lint, add the following to your analysis_options.yaml file:

custom_lint:
  rules:
    - specific_lint_rule: false # disable specific_lint_rule

To disable all lints and only enable the one you want, edit your analysis_options.yaml file as below:

custom_lint:
  enable_all_lint_rules: false # disable all lints
  rules:
    - specific_lint_rule # enable specific_lint_rule

Some lints have additional configuration options. To configure a lint, follow the example below:

custom_lint:
  rules:
    - configurable_lint_rule:
      option1: value1
      option2: value2

Dart lints

avoid_duplicate_import

Duplicate imports are unnecessary.

Bad

import 'dart:math' as math show max;
import 'dart:math';

final a = math.max(1, 10);
final b = min(1, 10);

Good

import 'dart:math' as math show max, min;

final a = math.max(1, 10);
final b = math.min(1, 10);

avoid_dynamic

Using dynamic sacrifices the benefits of static typing and decreases code readability. Only use dynamic when necessary.

Using dynamic with Map will not trigger this lint.

Bad

dynamic thing = 'text';
void log(dynamic something) => print(something);
List<dynamic> list = [1, 2, 3];
final setLiteral = <dynamic>{'a', 'b', 'c'};

Good

String thing = 'text';
void log(String something) => print(something);
List<int> list = [1, 2, 3];
final setLiteral = <String>{'a', 'b', 'c'};

avoid_empty_block

Empty block usually indicates a missing implementation.

Bad

void doSomething() {

}

Good

void doSomething() {
  actuallyDoSomething();
}

void doSomething() {}
  // TODO: implement doSomething
}

avoid_inverted_boolean_expression

Inverted boolean expression decreases code readability.

Bad

if (!(number == 0)) {}
if (!(number > 0)) {}
final anotherNumber = !(number == 0) ? 1 : 2;

Good

if (number != 0) {}
if (number <= 0) {}
final anotherNumber = number != 0 ? 2 : 1;

Fix

max_lines_for_file

A file should not exceed a certain number of lines.

Options: max_lines (default: 200)

max_lines_for_function

A function should not exceed a certain number of lines.

Options: max_lines (default: 100)

prefer_declaring_const_constructor

Constructors of classes with only final fields should be declared as const constructors when possible.

Bad

class Point {
  final double x;
  final double y;

  Point(this.x, this.y);

  Point.origin()
      : x = 0,
        y = 0;
}

Good

class Point {
  final double x;
  final double y;

  const Point(this.x, this.y);

  const Point.origin()
      : x = 0,
        y = 0;
}

Fix

prefer_declaring_parameter_name

Not declaring parameter name decreases code readability and the IDEs code completion will not be able to suggest the parameter name.

Bad

typedef ItemBuilder = Widget Function(BuildContext, int);

Good

typedef ItemBuilder = Widget Function(BuildContext context, int index);

prefer_immediate_return

Declaring a variable to return it on the next line is unnecessary.

Bad

int add(int a, int b) {
  final result = a + b;
  return result;
}

Good

int add(int a, int b) {
  return a + b;
}

Fix

prefer_iterable_first

Using iterable.first increases code readability.

Bad

const numbers = [1, 2, 3];
int firstNumber;

firstNumber = numbers[0];
firstNumber = numbers.elementAt(0);

Good

const numbers = [1, 2, 3];
int firstNumber;

firstNumber = numbers.first;

Fix

prefer_iterable_last

Using iterable.last increases code readability.

Bad

const numbers = [1, 2, 3];
int lastNumber;

lastNumber = numbers[numbers.length - 1];
lastNumber = numbers.elementAt(numbers.length - 1);

Fix

Good

const numbers = [1, 2, 3];
int lastNumber;

lastNumber = numbers.last;

prefer_underscore_for_unused_callback_parameters

Using _ for unused callback parameters increases code readability.

Bad

itemBuilder: (context, index) {
  return Text('Item $index');
}

Good

itemBuilder: (_, index) {
  return Text('Item $index');
}

Flutter lints

avoid_single_child_in_flex

Using Column or Row with only one child is inefficient.

Bad

Row(
  children: [
    Container(),
  ],
)

Good

Align(
  child: Container(),
)

// or

Center(
  child: Container(),
)

Fix

correct_order_for_super_dispose

super.dispose() should be called at the end of the dispose method.

Bad

@override
void dispose() {
  super.dispose();
  _dispose();
}

Good

@override
void dispose() {
  _dispose();
  super.dispose();
}

Fix

correct_order_for_super_init_state

super.initState() should be called at the start of the initState method.

Bad

@override
void initState() {
  _init();
  super.initState();
}

Good

@override
void initState() {
  super.initState();
  _init();
}

Fix

prefer_async_callback

There is a typedef AsyncCallback defined in flutter.

Bad

final Future<void> Function() cb;

Good

final AsyncCallback cb;

prefer_border_from_border_side

Border.all is not a const constructor and it uses const constructor Border.fromBorderSide internally.

Bad

DecoratedBox(
  decoration: BoxDecoration(
    border: Border.all(
      width: 1,
      style: BorderStyle.solid,
    ),
  ),
)

Good

const DecoratedBox(
  decoration: BoxDecoration(
    border: Border.fromBorderSide(
      BorderSide(
        width: 1,
        style: BorderStyle.solid,
      ),
    ),
  ),
)

Fix

prefer_border_radius_all

BorderRadius.all is not a const constructor and it uses const constructor BorderRadius.circular internally.

Bad

DecoratedBox(
  decoration: BoxDecoration(
    borderRadius: BorderRadius.circular(8),
  ),
)

Good

const DecoratedBox(
  decoration: BoxDecoration(
    borderRadius: BorderRadius.all(Radius.circular(8)),
  ),
)

Fix

prefer_dedicated_media_query_method

Using MediaQuery.of(context) to access below properties will cause unnecessary rebuilds.

• accessibleNavigation
• alwaysUse24HourFormat
• boldText
• devicePixelRatio
• disableAnimations
• displayFeatures
• gestureSettings
• highContrast
• invertColors
• navigationMode
• orientation
• padding
• platformBrightness
• size
• systemGestureInsets
• textScaleFactor
• viewInsets
• viewPadding

Bad

final size = MediaQuery.of(context).size;
final orientation = MediaQuery.maybeOf(context)?.orientation;

Good

final size = MediaQuery.of(context).size;
final orientation = MediaQuery.maybeOrientationOf(context);

Fix

prefer_spacer

Using Expanded with an empty Container or SizedBox is inefficient.

Bad

Column(
  children: [
    Expanded(
      flex: 2,
      child: SizedBox(),
    ),
  ],
)

Good

Column(
  children: [
    Spacer(flex: 2),
  ],
)

Fix

prefer_text_rich

RichText does not inherit TextStyle from DefaultTextStyle.

Bad

RichText(
  text: const TextSpan(
    text: 'Pyramid',
    children: [
      TextSpan(text: 'Lint'),
    ],
  ),
)

Good

const Text.rich(
  TextSpan(
    text: 'Pyramid',
    children: [
      TextSpan(text: 'Lint'),
    ],
  ),
)

Fix

prefer_value_changed

There is a typedef ValueChanged defined in flutter.

Bad

final void Function(int) cb;

Good

final ValueChanged<int> cb;

prefer_void_callback

There is a typedef VoidCallback defined in flutter.

Bad

final void Function() cb;

Good

final VoidCallback cb;

proper_controller_dispose

Controllers should be disposed in dispose method.

• AnimationController
• PageController
• ScrollController
• SearchController
• TabController
• TextEditingController
• UndoHistoryController

Bad

class _MyWidgetState extends State<MyWidget> {
  final _textEditingController = TextEditingController();

  @override
  Widget build(BuildContext context) {
    return Container();
  }
}

Good

class _MyWidgetState extends State<MyWidget> {
  final _textEditingController = TextEditingController();

  @override
  Widget build(BuildContext context) {
    return Container();
  }

  @override
  void dispose() {
    _textEditingController.dispose();
    super.dispose();
  }
}

proper_edge_insets_constructor

EdgeInsets.all(0) should be replaced with EdgeInsets.zero.

Bad

padding = const EdgeInsets.fromLTRB(0, 0, 0, 0);
padding = const EdgeInsets.fromLTRB(8, 8, 8, 8);
padding = const EdgeInsets.fromLTRB(8, 0, 8, 0);
padding = const EdgeInsets.fromLTRB(8, 4, 8, 4);
padding = const EdgeInsets.fromLTRB(8, 4, 8, 0);

padding = const EdgeInsets.only(left: 0, top: 0, right: 0, bottom: 0);
padding = const EdgeInsets.only(left: 8, top: 8, right: 8, bottom: 8);
padding = const EdgeInsets.only(left: 8, top: 0, right: 8, bottom: 0);
padding = const EdgeInsets.only(left: 8, top: 4, right: 8, bottom: 4);
padding = const EdgeInsets.only(left: 2, top: 4, right: 6, bottom: 8);

padding = const EdgeInsets.symmetric(horizontal: 0, vertical: 0);
padding = const EdgeInsets.symmetric(horizontal: 8, vertical: 8);
padding = const EdgeInsets.symmetric(horizontal: 8, vertical: 0);

Good

padding = EdgeInsets.zero;
padding = const EdgeInsets.all(8);
padding = const EdgeInsets.symmetric(horizontal: 8);
padding = const EdgeInsets.symmetric(horizontal: 8, vertical: 4);
padding = const EdgeInsets.only(left: 8, top: 4, right: 8);

padding = EdgeInsets.zero;
padding = const EdgeInsets.all(8);
padding = const EdgeInsets.symmetric(horizontal: 8);
padding = const EdgeInsets.symmetric(horizontal: 8, vertical: 4);
padding = const EdgeInsets.fromLTRB(2, 4, 6, 8);

padding = EdgeInsets.zero;
padding = const EdgeInsets.all(8);
padding = const EdgeInsets.symmetric(horizontal: 8);

Fix

proper_usage_of_expanded_and_flexible

Expanded and Flexible should be placed inside a Row, Column, or Flex.

Bad

Center(
  child: Expanded(
    child: Container(),
  ),
)

Good

Row(
  children: [
    Expanded(
      child: Container(),
    ),
  ],
)

proper_usage_of_from_environment

bool.fromEnvironment, int.fromEnvironment and String.fromEnvironment constructors should be invoked as const.

Bad

final boolean = bool.fromEnvironment('bool');
int integer = int.fromEnvironment('int');
var string = String.fromEnvironment('String');

Good

const boolean = bool.fromEnvironment('bool');
const integer = int.fromEnvironment('int');
const string = String.fromEnvironment('String');

Dart assists

invert_boolean_expression

Invert a boolean expression.

swap_then_else_expression

Swap the then and else expression of a if-else expression or conditional expression.

Flutter assists

use_edge_insets_zero

Replace

• EdgeInsets.all(0)
• EdgeInsets.fromLTRB(0, 0, 0, 0)
• EdgeInsets.only(left: 0, top: 0, right: 0, bottom: 0)
• EdgeInsets.symmetric(horizontal: 0, vertical: 0)

with EdgeInsets.zero.

wrap_with_expanded

Wrap the selected widget with an Expanded.

wrap_with_layout_builder

Wrap the selected widget with a LayoutBuilder.

wrap_with_stack

Wrap the selected widget with a Stack.