Eslint-plugin-headers NPM

eslint-plugin-headers

A flexible and --fixable rule for checking, inserting, and formatting file headers.

Supports variable content injection, configurable usage of block or line comments, custom comment block prefixes and suffixes, custom line prefixes, and spacing between the header and code.

Useful for inserting, enforcing, and updating copyright or licensing notices while preserving pragma expressions in leading content blocks.

Installation

You'll first need to install ESLint:

npm i eslint --save-dev

Next, install eslint-plugin-headers:

npm install eslint-plugin-headers --save-dev

Usage

Add headers to the plugins section of your .eslintrc configuration file. You can omit the eslint-plugin- prefix:

{
  "plugins": ["headers"]
}

Then configure the rules you want to use under the rules section.

{
  "rules": {
    "headers/header-format": [
      "error",
      {
        "source": "string",
        "content": "Copyright 2024. All rights reserved."
      }
    ]
  }
}

Example 0:

Using the configuration from above, here's a file without a matching header:

module.exports = 42;

When the fix is applied, the file now appears so:

/**
 * Copyright 2024. All rights reserved.
 */
module.exports = 42;

Example 1:

Using the same configuration, this file already has a header, this one containing pragmas:

/**
 * @fileoverview This file contains a magic number.
 * @author Rob Misasi
 */
module.exports = 42;

When the fix is applied, the file now appears so:

/**
 * Copyright 2024. All rights reserved.
 *
 * @fileoverview This file contains a magic number.
 * @author Rob Misasi
 */
module.exports = 42;

Example 2: Using the following configuration, variable values can be injected into the provided header:

{
  "rules": {
    "headers/header-format": [
      "error",
      {
        "source": "string",
        "content": "Copyright {year} {company}. All rights reserved.",
        "variables": {
          "year": "2077",
          "company": "Software Incorporated"
        }
      }
    ]
  }
}

We can then apply a fix to the following file:

/**
 * Copyright 1947 Hardware LLC. All rights reserved.
 */
module.exports = 42;

And get the resulting header:

/**
 * Copyright 2077 Software Incorporated. All rights reserved.
 */
module.exports = 42;

Options

Options are supplied through a single object with the following properties:

Name	Type	Required	Default	Description
source	"file" \| "string"	Yes		Indicates how the header content is supplied.
style	"line" \| "jsdoc"	No	"jsdoc"	Indicates the comment style to enforce. A leading line-style comment block will only include adjacent line comments, although a line comment's content may be empty.
content	string	When `source: "string"`		The string to enforce in the header comment.
path	string	When `source: "file"`		The path to a file containing the header content to enforce.
preservePragmas	boolean	No	`true`	Preserves existing pragma expressions in leading comments when updating header. No effect when `style: "line"`.
blockPrefix	string	No	"*" + newline when `style: "jsdoc"`	Content at the start of the leading comment block.
blockSuffix	string	No	newline + " " when `style: "jsdoc"`	Content at the end of the leading comment block.
linePrefix	string	No	" * " when `style: "jsdoc"`, " " when `style: "line"`	Content prepended to the start of each line of content.
trailingNewlines	number	No		Number of empty lines to enforce after the leading comment.
variables	object	No		The keys to find and values to fill when formatting the provided header. Values must be strings.