eslint-plugin-sonarjs

SonarJS rules for ESLint to detect bugs and suspicious patterns in your code.

Rules

Bug Detection 🐛

Rules in this category aim to find places in code which have a high chance of being bugs, i.e. don't work as intended.

• All branches in a conditional structure should not have exactly the same implementation (no-all-duplicated-branches)
• Collection elements should not be replaced unconditionally (no-element-overwrite)
• Empty collections should not be accessed or iterated (no-empty-collection)
• Function calls should not pass extra arguments (no-extra-arguments)
• Related "if/else if" statements should not have the same condition (no-identical-conditions)
• Identical expressions should not be used on both sides of a binary operator (no-identical-expressions)
• Loops with at most one iteration should be refactored (no-one-iteration-loop)
• The output of functions that don't return anything should not be used (no-use-of-empty-return-value)
• Non-existent operators '=+', '=-' and '=!' should not be used (non-existent-operator)

Code Smell Detection 🐷

Code Smells, or maintainability issues, are raised for places of code which might be costly to change in the future. These rules also help to keep the high code quality and readability. And finally some rules report issues on different suspicious code patters.

• Cognitive Complexity of functions should not be too high (cognitive-complexity)
• "switch" statements should not have too many "case" clauses (max-switch-cases)
• Collapsible "if" statements should be merged (no-collapsible-if)
• Collection sizes and array length comparisons should make sense (no-collection-size-mischeck)
• String literals should not be duplicated (no-duplicate-string)
• Two branches in a conditional structure should not have exactly the same implementation (no-duplicated-branches)
• Functions should not have identical implementations (no-identical-functions)
• Boolean checks should not be inverted (no-inverted-boolean-check) (:wrench: fixable)
• "switch" statements should not be nested (no-nested-switch)
• Template literals should not be nested (no-nested-template-literals)
• Boolean literals should not be redundant (no-redundant-boolean)
• Jump statements should not be redundant (no-redundant-jump)
• Conditionals should start on new lines (no-same-line-conditional)
• "switch" statements should have at least 3 "case" clauses (no-small-switch)
• Collection and array contents should be used (no-unused-collection)
• "catch" clauses should do more than rethrow (no-useless-catch)
• Local variables should not be declared and then immediately returned or thrown (prefer-immediate-return) (:wrench: fixable)
• Object literal syntax should be used (prefer-object-literal)
• Return of boolean expressions should not be wrapped into an "if-then-else" statement (prefer-single-boolean-return)
• A "while" loop should be used instead of a "for" loop (prefer-while) (:wrench: fixable)

Prerequisites

Node.js (>=10.x).

Usage

• If you don't have ESLint yet configured for your project, follow these instructions.
• Install eslint-plugin-sonarjs using npm (or yarn) for you project or globally:

npm install eslint-plugin-sonarjs --save-dev # install for your project
npm install eslint-plugin-sonarjs -g         # or install globally

• Add eslint-plugin-sonarjs to the plugins option of your .eslintrc:

{
  "plugins": ["sonarjs"]
}

• Add plugin:sonarjs/recommended to the extends option to enable all recommended rules:

{
  "extends": ["plugin:sonarjs/recommended"]
}

• or enable only some rules manually:

{
  "rules": {
    "sonarjs/cognitive-complexity": "error",
    "sonarjs/no-identical-expressions": "error"
    // etc.
  }
}

Contributing

You want to participate in the development of the project? Have a look at our contributing guide!