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Linting TypeScript

Last modified: 26 July 2022

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You can use the TSLint code verification tool from inside PyCharm and check your TypeScript code for most common mistakes without running the application. When the tool is activated, it lints all the opened TypeScript files and marks the detected problems.

To view the description of a problem, hover over the highlighted code. By default, PyCharm marks detected problems based on the severity levels from the TSLint configuration file. See Configuring TSLint highlighting to learn how to override these settings.

TSLint: errors and warnings are highlighted, the description of a problem is shown in a tooltip.

You can also check your TypeScript code with ESLint, see Lint TypeScript with ESLint.

Before you start

Installing TSLint

Activating and configuring TSLint in PyCharm

By default, PyCharm uses the TSLint package from the project node_modules folder and the tslint.json configuration file from the folder where the current file is stored. If no tslint.json is found in the current file folder, PyCharm will look for one in its parent folders up to the project root.

If you have several package.json files with TSLint listed as a dependency, PyCharm starts a separate process for each package.json and processes everything below it. This lets you apply a specific TSLint version or a specific set of plugins to each path in a monorepo or a project with multiple TSLint configurations.

This behavior is default in all new PyCharm projects. To enable it in a previously created project, go to Languages & Frameworks | TypeScript | TSLint in the Settings/Preferences dialog (Ctrl+Alt+S) and select the Automatic TSLint configuration option.

You can also configure TSLint manually to use a custom TSLint package and tslint.json and specify some additional rules.

Configuring highlighting for TSLint

By default, PyCharm marks the detected errors and warnings based on the severity levels from the TSLint configuration file. For example, errors are highlighted with a red squiggly line, while warnings are marked with a yellow background. See Code inspections and Change inspection severity for details.

Change the severity level of a rule in the TSLint configuration

  • In TSLint configuration file, locate the rule you want to edit and set its ID to warning or to error. Learn more from the TSLint official website.

You can override the severities from the TSLint configuration file so that PyCharm ignores them and shows everything reported by the linter as errors, warnings, or in a custom color.

Ignore the severity levels from the configuration

  1. In the Settings/Preferences dialog (Ctrl+Alt+S), go to Editor | Inspections. The Inspections page opens.

  2. In the central pane, go to TypeScript | TSLint.

  3. In the right-hand pane, clear the Use rule severity from the configuration file checkbox and select the severity level to use instead of the default one.

    Specifying a custom severity level for TSLint

Importing code style from a TSLint configuration file

PyCharm understands some of the TSLint rules described in tslint.json, tslint.yaml, or tslint.yml configuration files and lets you apply them to the TypeScript code style configuration in your project.

  • When you open your project for the first time, PyCharm imports the code style from the project tslint.json, tslint.yaml, or tslint.yml automatically.

  • If tslint.json, tslint.yaml, or tslint.yml is updated (manually or from your version control), open it in the editor and choose Apply TSLint Code Style Rules from the context menu.

    Import TSLint code style rules from the editor: context menu

    Alternatively, just answer Yes to the "Apply code style from TSLint?" question on top of the file.

    PyCharm suggests importing the code style from tslint.json

TSLint quick-fixes

PyCharm lets you automatically fix some of the issues reported by TSLint.

You can suppress TSLint rules for the current file and even for the current line. PyCharm automatically generates disable comments in the format /* tslint:disable:<rule name> or // tslint:disable-next-line:<rule name> and places them on top of the file or above the current line respectively.

Suppress a TSLint rule on the fly

  1. Place the cursor at an error or a warning reported by TSLint and press Alt+Enter.

  2. Select the quick-fix for the rule that you want to disable and press Right.

  3. From the list, select Suppress <rule name> for current file or Suppress <rule name> for current line.

    Disabling TSLint rules on the fly by adding disable comments

Lint TypeScript code with ESLint

With PyCharm, you can also check your TypeScript code with ESLint which brings a wide range of linting rules that can also be extended with plugins. PyCharm shows warnings and errors reported by ESLint right in the editor, as you type. Learn more from ESLint.

PyCharm highlights errors reported by ESLint in .ts and .tsx files when @typescript-eslint/parser is set as a parser in your project ESLint configuration. Learn more from the readme file in the typescript-eslint repo.

Install and configure ESLint

  1. In the embedded Terminal (Alt+F12) , type one of the following commands:

    • npm install --g eslint for global installation.

    • npm install --save-dev eslint to install ESLint as a development dependency.

  2. By default, ESLint is disabled. Enable it as described in Activate and configure ESLint in PyCharm".

Use ESLint for TypeScript in a new project

  1. In the embedded Terminal (Alt+F12) , type:

    npm install @typescript-eslint/parser @typescript-eslint/eslint-plugin --save-dev

    note

    If you installed ESLint globally, install @typescript-eslint/eslint-plugin globally as well. Learn more about installation and versions compatibility from the @typescript-eslint/eslint-plugin official documentation.

  2. In the .eslintrc configuration file or under eslintConfig in package.json, add:

    {
    "parser": "@typescript-eslint/parser",
    "plugins": [
        "@typescript-eslint"
    ],
    "extends": [
        "plugin:@typescript-eslint/recommended"
    ]
}

Suppress linting TypeScript code with ESLint

  • If you are already using @typescript-eslint/parser but you do not want to check TypeScript code with ESLint, add .ts or .tsx to the .eslintignore file.

ESLint 4.0

If you are using previous versions of ESLint, you have to install babel-eslint, typescript-eslint-parser, or eslint-plugin-typescript because ESLint 4.0 and earlier do not support scoped packages.

Use babel-eslint

  1. In the embedded Terminal (Alt+F12) , type:

    npm install eslint babel-eslint --save-dev

    Learn more about installation and versions compatibility from the babel-eslint official documentation.

  2. In the .eslintrc configuration file or under eslintConfig in package.json, add:

    {
    "parser": "babel-eslint"
}

Use typescript-eslint-parser

  1. In the embedded Terminal (Alt+F12) , type:

    npm install typescript-eslint-parser --save-dev

    Learn more from the typescript-eslint-parser official documentation.

  2. In the .eslintrc configuration file or under eslintConfig in package.json, add:

    {
    "parser": "typescript-eslint-parser"
}

Use eslint-plugin-typescript

  1. In the embedded Terminal (Alt+F12) , type:

    npm install typescript-eslint-parser eslint-plugin-typescript --save-dev

    note

    If you installed ESLint globally, install eslint-plugin-typescript globally as well. Learn more from the eslint-plugin-typescript official documentation.

  2. In the .eslintrc configuration file or under eslintConfig in package.json, add:

    {
    "parser": "typescript-eslint-parser",
    "plugins": [
        "eslint-plugin-typescript"
    ]
}

See also

Procedures

External Links