tslint

What is tslint?

The tslint npm package is a static analysis tool that checks TypeScript code for readability, maintainability, and functionality errors. It is widely used to enforce a consistent code style by checking the code against a set of linting rules.

What are tslint's main functionalities?

Linting TypeScript Files

This feature allows you to lint TypeScript files by specifying a configuration file and a pattern to match files. The command will process all TypeScript files in the 'src' directory and its subdirectories.

tslint -c tslint.json 'src/**/*.ts'

Fixing Linting Errors Automatically

This feature automatically fixes linting errors that can be corrected without human intervention. It is useful for fixing simple issues like whitespace or semicolon usage.

tslint --fix -c tslint.json 'src/**/*.ts'

Custom Rules

This feature allows you to use custom linting rules in addition to the predefined rules. You can specify a directory containing custom rule definitions to be applied to your code.

tslint -c tslint.json 'src/**/*.ts' --rules-dir custom_rules

Other packages similar to tslint

eslint

ESLint is a popular linting tool for JavaScript and TypeScript. It is highly configurable and extendable, with a large ecosystem of plugins. ESLint has effectively replaced TSLint as the preferred linter for TypeScript after TSLint's deprecation.

prettier

Prettier is an opinionated code formatter that supports many languages, including TypeScript. While it does not perform static code analysis, it formats code to a consistent style. Prettier can be used alongside linters like ESLint.

stylelint

Stylelint is a modern linter that helps you avoid errors and enforce conventions in your stylesheets. Although it is primarily used for CSS, it can be used in conjunction with PostCSS to lint SCSS, Sass, Less, and other CSS-like languages.

README

tslint

A linter for the TypeScript language.

Supported Rules

• ban bans the use of specific functions. Options are ["object", "function"] pairs that ban the use of object.function()
• class-name enforces PascalCased class and interface names.
• comment-format enforces rules for single-line comments. Rule options:
  • "check-space" enforces the rule that all single-line comments must begin with a space, as in // comment
  • "check-lowercase" enforces the rule that the first non-whitespace character of a comment must be lowercase, if applicable
• curly enforces braces for if/for/do/while statements.
• eofline enforces the file to end with a newline.
• forin enforces a for ... in statement to be filtered with an if statement.*
• indent enforces consistent indentation levels (currently disabled).
• interface-name enforces the rule that interface names must begin with a capital 'I'
• label-position enforces labels only on sensible statements.
• label-undefined checks that labels are defined before usage.
• max-line-length sets the maximum length of a line.
• no-arg disallows access to arguments.callee.
• no-bitwise disallows bitwise operators.
• no-console disallows access to the specified functions on console. Rule options are functions to ban on the console variable.
• no-consecutive-blank-lines disallows having more than one blank line in a row in a file
• no-construct disallows access to the constructors of String, Number, and Boolean.
• no-debugger disallows debugger statements.
• no-duplicate-key disallows duplicate keys in object literals.
• no-duplicate-variable disallows duplicate variable declarations.
• no-empty disallows empty blocks.
• no-eval disallows eval function invocations.
• no-string-literal disallows object access via string literals.
• no-trailing-whitespace disallows trailing whitespace at the end of a line.
• no-unreachable disallows unreachable code after break, catch, throw, and return statements.
• one-line enforces the specified tokens to be on the same line as the expression preceding it. Rule options:
  • "check-catch" checks that catch is on the same line as the closing brace for try
  • "check-else" checks that else is on the same line as the closing brace for if
  • "check-open-brace" checks that an open brace falls on the same line as its preceding expression.
  • "check-whitespace" checks preceding whitespace for the specified tokens.
• quotemark enforces consistent single or double quoted string literals.
• radix enforces the radix parameter of parseInt
• semicolon enforces semicolons at the end of every statement.
• triple-equals enforces === and !== in favor of == and !=.
• typedef enforces type definitions to exist. Rule options:
  • "callSignature" checks return type of functions
  • "catchClause" checks type in exception catch blocks
  • "indexSignature" checks index type specifier of indexers
  • "parameter" checks type specifier of parameters
  • "propertySignature" checks return types of interface properties
  • "variableDeclarator" checks variable declarations
• typedef-whitespace enforces spacing whitespace for type definitions. Each rule option requires a value of "space" or "nospace" to require a space or no space before the type specifier's colon. Rule options:
  • "callSignature" checks return type of functions
  • "catchClause" checks type in exception catch blocks
  • "indexSignature" checks index type specifier of indexers
• variable-name allows only camelCased or UPPER_CASED variable names. Rule options:
  • "allow-leading-underscore" allows underscores at the beginnning.
• whitespace enforces spacing whitespace. Rule options:
  • "check-branch" checks branching statements (if/else/for/while) are followed by whitespace
  • "check-decl"checks that variable declarations have whitespace around the equals token
  • "check-operator" checks for whitespace around operator tokens
  • "check-separator" checks for whitespace after separator tokens (,/;)
  • "check-type" checks for whitespace before a variable type specification

Installation

CLI

sudo npm install tslint -g

Library

npm install tslint

Usage

Please first ensure that the TypeScript source files compile correctly.

CLI

usage: tslint

Options:
  -c, --config  		 configuration file
  -f, --file    		 file to lint                 [required]
  -o, --out     		 output file
  -r, --rules-dir   	 rules directory
  -s, --formatters-dir   formatters directory
  -t, --format  		 output format (prose, json)  [default: "prose"]

By default, configuration is loaded from .tslintrc or tslint.json, if either exists in the current path.

Library

var options = {
	formatter: "json",
    configuration: configuration,
    rulesDirectory: "customRules/",
    formattersDirectory: "customFormatters/"
};

var Linter = require("tslint");

var ll = new Linter(fileName, contents, options);
var result = ll.lint();

Development

Setup

git clone [e-mail]:palantir/tslint.git
cd tslint
git submodule init
git submodule update

Build

npm install
grunt

TODO

• Add more rules from jshint
• Disallow variables referenced outside of their scope definition
• Disallow unused variables
• Support pluggable formatters