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eslint-plugin-headers

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

Supports variable content injection, regex pattern matching, 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.

This plugin is best used with a formatter like prettier.

Motivation

This plugin aims to be a successor to the popular but defunct plugin eslint-plugin-header. eslint-plugin-headers strives to implement the same features as eslint-plugin-header where possible, while sensibly extending features, supporting modern JavaScript frameworks, and maintaining compatibility with other common tools.

Installation

You'll first need to install ESLint:

Next, install eslint-plugin-headers:

Usage

Flat config

Import the default export from the estlin-plugin-headers module. Add the headers key to the plugins section of your config object in the configuration file. You can omit the eslint-plugin- prefix:

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

Legacy .eslintrc config

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

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

Usage with Vue

This project supports parsing Vue files via the AST generated by the vue-eslint-parser package. To properly apply this plugin's rules to Vue files, you must:

1. Install the vue-eslint-parser package as a dev dependency. 2. Specify the vue-eslint-parser in the configuration's languageOptions.parser field (or the "parser" field for legacy configurations), and 3. Set the enableVueSupport flag for the appropriate rules.

Example configuration:

With this configuration the following file would be transformed like so:

Before:

After applying the fix:

Since the vue-eslint-parser package strives to maintain compatibility with rules targeting JavaScript, it exposes Vue AST tokens to rules in different ways than the default ESlint parser. The means of exposing HTML Comment nodes are of specific interest to this plugin, and the mechanism to access these are substantially different than how a plugin would typically read a comment node, making it necessary to both specify this particular parser as well as setting the flag.

Examples

Example 0:

Example Configuration:

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

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

Example 1:

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

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

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

We can then apply a fix to the following file:

And get the resulting header:

Example 3:

Using the following configuration, patterns are used to validate content in existing headers:

The following file would validate successfully:

Alternatively, the plugin can apply a fix to the following invalid file:

And get the following header:

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. No effect if enableVueSupport: true. | | 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 | See below | Content at the start of the leading comment block. | | blockSuffix | string | No | See below | Content at the end of the leading comment block. | | linePrefix | string | No | See below | 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. | | patterns | { [key: string] : { pattern: string; defaultValue?: string; } } | No | | The keys to find and Regex patterns to validate when matching the provided header. WARNING! Default values must be provided for errors to be --fixable. | | enableVueSupport | boolean | No | false | EXPERIMENTAL! Enable support for parsing .vue files. Must be used with vue-eslint-parser. See above for details. |

Default Prefixes and Suffixes

Example configuration:

The subsequent section titles contain the additional configuration inserted above, and the resulting comment that will be produced.

style: "line"

Expected/produced header:

• Default block prefix: None • Default block suffix: None • Default line prefix: " "

style: "jsdoc"

Expected/produced header:

• Default block prefix: "*\n" • Default block suffix: "\n " • Default line prefix: " * "

enableVueSupport: true

Expected/produced header:

• Default block prefix: "\n" • Default block suffix: "\n" • Default line prefix: " "

Future

• Add support for common pragma expressions that don't utilize the @ symbol (e.g. eslint-disable)

Rules

🔧 Automatically fixable by the --fix CLI option.

| Name | Description | 🔧 |

| header-format | Verifies the content and format of a file's leading comment block. | 🔧 |

Description from the npm listing.