Custom Linter

A Set of Custom Linting Rules for Dart and Flutter
Designed to improve code quality and enforce development standards.

BSD 3-Clause License

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About

custom_linter is a package of custom linting rules built using custom_lint. It helps developers maintain clean and readable code in Dart and Flutter projects by detecting potential issues such as magic numbers, empty blocks, or commented-out code.

The project includes the following rules:

• no_null_assert: Prohibits the use of the ! operator for null assertion.
• avoid_large_methods: Limits the size of methods to a specified number of lines.
• no_forbidden_class_names: Disallows the use of specific class names.
• no_forbidden_method_names: Disallows the use of specific method names.
• avoid_magic_numbers: Requires replacing magic numbers with named constants.
• prefer_ink_well_over_gesture_detector: Recommends using InkWell over GestureDetector for simple tap events.
• no_empty_blocks: Prohibits empty code blocks (excluding those with comments).

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Installation

1. Setting Up the custom_linter Package

If you want to use this project as a standalone package:

1. Clone the repository:

  git clone <repository_url>
  cd custom_linter

2. Install dependencies:

  dart pub get

2. Adding to Your Project

Add custom_lint and custom_linter to your application's pubspec.yaml:

dev_dependencies:
  custom_lint: ^0.7.0
  custom_linter:
    path: ../custom_linter  # Specify the path to the custom_linter folder

3. Configuring analysis_options.yaml

Enable the custom_lint plugin and activate the desired rules:

include: package:flutter_lints/flutter.yaml

analyzer:
  plugins:
    - custom_lint

custom_lint:
  rules:
    - no_null_assert
    - no_empty_blocks
    - avoid_magic_numbers
    - prefer_ink_well_over_gesture_detector
    - no_forbidden_class_names:
        forbidden_names: [Test, Demo, Example]
    - no_forbidden_method_names:
        forbidden_names: [execute, perform, fetch]
    - avoid_large_methods:
        max_lines: 5

Usage

1. After setup, run:

  flutter pub get

2. Analyze your code:

  flutter pub run custom_lint

3. Check the console or IDE output for lint violations.

Rule Descriptions

no_null_assert

• Description: Prohibits the use of the ! operator for null assertion to avoid potential NullPointerExceptions.
• Example: String? s; print(s!); → Triggers a warning.

avoid_large_methods

• Description: Limits the maximum number of lines in a method (default is 100, configurable via max_lines).
• Example: A method with 6 lines with max_lines: 5 triggers a warning.

no_forbidden_class_names

• Description: Disallows the use of specified class names (configurable via forbidden_names).
• Example: class Test {} → Triggers if Test is in the forbidden list.

no_forbidden_method_names

• Description: Disallows the use of specified method names (configurable via forbidden_names).
• Example: void execute() {} → Triggers if execute is forbidden.

avoid_magic_numbers

• Description: Requires replacing numbers (except 0 and 1) with named constants.
• Example: var x = 42; → Triggers a warning.

prefer_ink_well_over_gesture_detector

• Description: Recommends using InkWell instead of GestureDetector for simple tap events to provide visual feedback.
• Example: GestureDetector(onTap: () {}, child: Text('Tap')) → Triggers.

no_empty_blocks

• Description: Prohibits empty code blocks but ignores blocks with comments.
• Example: if (true) {} → Triggers; if (true) { // comment } → Does not trigger.

Debugging

To enable debug output, add the following to analysis_options.yaml:

custom_lint: debug: true verbose: true

Logs will be written to custom_lint.log next to pubspec.yaml.

Testing

An example project is provided in the example directory at the root of this project to demonstrate rule violations and expected lints. To test the rules, navigate to the example directory and run the following:

flutter pub get

Then analyze the code:

flutter pub run custom_lint

If expected lints do not trigger, the command will fail. Check the example/lib/main.dart file for sample code with annotated violations.