eslint-plugin-yet-another-license-header

This repo contains yet another eslint plugin for handling a license header comment at the top of your JavaScript/TypeScript files.

It includes a single rule, header, that will (a) report an issue if the top comment block in a checked file does not match the configured header string (or the allowed patterns) and (b) can fix (with eslint --fix) the issue by updating or adding a top comment block.

Why?

• There is eslint-plugin-header. AFAIK, this plugin does not support eslint@9. It can also accidentally blow away a top-comment.
• There is eslint-plugin-license-header. I like this plugin. However, it does not support having multiple allowed headers, or a pattern for allowed headers. The opentelemetry-js-contrib requires this functionality. I have a PR on eslint-plugin-license-header for this, which hopefully will eventually be included, in some form.

If you run into some issue with this plugin, it is very possible that the above plugins are better battle-tested.

Compatibility

Currently this is written to support eslint@9. As well, the node versions supported (see package.json#engines) are selected to match that for eslint@9.

(I'm open to supporting earlier node versions and earlier eslint versions.)

Usage

1. Install it.

   npm install --save-dev eslint-plugin-yet-another-license-header

2. Add it to your ESLint config file, e.g. "eslint.config.mjs":

   import {defineConfig} from 'eslint/config';
   import headerPlugin from 'eslint-plugin-yet-another-license-header';
   
   const header = `
   /*
    * Copyright Trent Mick
    * SPDX-License-Identifier: Apache-2.0
    */
   `;
   
   export default defineConfig([
       {
           plugins: {
               'yet-another-license-header': headerPlugin,
           },
           rules: {
               'yet-another-license-header/header': [
                   'error',
                   {
                       header,
                       // Or use `headerFile` to point to the header content.
                       //      headerFile: './etc/header.txt',
   
                       // Optionally provide patterns.
                       allowedHeaderPatterns: [
                           // Allow additional copyrights after "Trent Mick".
                           /^\/\*\n \* Copyright Trent Mick(, .+)*\n \* SPDX-License-Identifier: Apache-2.0\n \*\/$/,
                       ],
                   },
               ],
               // ...
           },
       },
   ]);

3. Lint it.

   npx eslint

4. Fix it.

   npx eslint --fix

Configuration

The header rule is configured with a single object with the following properties:

header (string)

A string that is the default license header comment to check/add to the top of JS/TS files. Leading and trailing whitespace is removed.

One of header or headerFile must be specified.

headerFile (string)

A path to a file that contains the default license header comment. Leading and trailing whitespace is removed.

One of header or headerFile must be specified.

allowedHeaderPatterns (Array<RegExp|String>)

An optional array of allowed header patterns when checking if the lead comment block of a JS/TS file is acceptable. Note that the string from header (or headerFile) is always also used when checking an existing lead comment block. Elements of this array can be a string (checks for an exact match, after trimming) or a RegExp (tests via regexp.test(leadCommentBlock)).

[!WARNING] If you use allowedHeaderPatterns to support some variance on a default license header and something changes so that a file's header does not match, then eslint --fix will replace it with the string from header (or headerFile). This means it may delete some content you had intended to include in the license header block.