markdown/no-unused-definitions

A definition that no link or image uses is invisible in the rendered document. It's either left over from text that was removed, or the link that should use it has a typo. In markdown/gfm the same goes for footnote definitions.

Configure

Off by default. It needs an ESLint config that says which files are in the language:

import markdown from "@eslint/markdown";

export default [
  {
    files: ["**/*.md"],
    plugins: { markdown },
    language: "markdown/commonmark",
    rules: { "markdown/no-unused-definitions": "error" },
  },
];

It also works with markdown/gfm.

Examples

Reported:

Read the guide.

[guide]: https://example.com/guide

It is fast.

[^1]: On Linux.

Not reported:

Read the [guide].

[guide]: https://example.com/guide

Options

Option	Default	What it does
allowDefinitions	["//"]	Labels that don't have to be used.
allowFootnoteDefinitions	[]	Footnote labels that don't have to be used.
checkFootnoteDefinitions	true	Check footnote definitions too.

[//]: # (text) is a common way to write a comment, which is why // is allowed:

[//]: # (This is a comment)

[guide]: https://example.com/guide