Improve some docs

Author: wooorm

index.js

@@ -14,6 +14,9 @@
 import {matters} from 'micromark-extension-frontmatter/matters.js'
 
 /**
+ * Function that can be called to get an extension for
+ * `mdast-util-from-markdown`.
+ *
  * @param {Options} [options]
  * @returns {FromMarkdownExtension}
  */
@@ -64,6 +67,9 @@ function value(token) {
 }
 
 /**
+ * Function that can be called to get an extension for
+ * `mdast-util-to-markdown`.
+ *
  * @param {Options} [options]
  * @returns {ToMarkdownExtension}
  */

readme.md

@@ -8,32 +8,72 @@
 [![Backers][backers-badge]][collective]
 [![Chat][chat-badge]][chat]
 
-Extension for [`mdast-util-from-markdown`][from-markdown] and/or
-[`mdast-util-to-markdown`][to-markdown] to support frontmatter in **[mdast][]**.
-When parsing (`from-markdown`), must be combined with
-[`micromark-extension-frontmatter`][extension].
+[mdast][] extensions to parse and serialize frontmatter (YAML, TOML, and more).
+
+## Contents
+
+*   [What is this?](#what-is-this)
+*   [When to use this](#when-to-use-this)
+*   [Install](#install)
+*   [Use](#use)
+*   [API](#api)
+    *   [`frontmatterFromMarkdown(options?)`](#frontmatterfrommarkdownoptions)
+    *   [`frontmatterToMarkdown(options?)`](#frontmattertomarkdownoptions)
+*   [Syntax tree](#syntax-tree)
+    *   [Nodes](#nodes)
+    *   [Content model](#content-model)
+*   [Types](#types)
+*   [Compatibility](#compatibility)
+*   [Related](#related)
+*   [Contribute](#contribute)
+*   [License](#license)
+
+## What is this?
+
+This package contains extensions that add support for the frontmatter syntax
+enabled by GitHub and many other places to
+[`mdast-util-from-markdown`][mdast-util-from-markdown] and
+[`mdast-util-to-markdown`][mdast-util-to-markdown].
+
+Frontmatter is a metadata format in front of content.
+It’s typically written in YAML and is often used with markdown.
+Frontmatter does not work everywhere so it makes markdown less portable.
 
 ## When to use this
 
-Use this if you’re dealing with the AST manually.
-It’s probably nicer to use [`remark-frontmatter`][remark-frontmatter] with
-**[remark][]**, which includes this but provides a nicer interface and
-makes it easier to combine with hundreds of plugins.
+These tools are all rather low-level.
+In most cases, you’d want to use [`remark-frontmatter`][remark-frontmatter] with
+remark instead.
 
-## Install
+When working with `mdast-util-from-markdown`, you must combine this package with
+[`micromark-extension-frontmatter`][extension].
 
-This package is [ESM only](https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c):
-Node 12+ is needed to use it and it must be `import`ed instead of `require`d.
+## Install
 
-[npm][]:
+This package is [ESM only][esm].
+In Node.js (version 12.20+, 14.14+, or 16.0+), install with [npm][]:
 
 ```sh
 npm install mdast-util-frontmatter
 ```
 
+In Deno with [`esm.sh`][esmsh]:
+
+```js
+import {frontmatterFromMarkdown, frontmatterToMarkdown} from 'https://esm.sh/mdast-util-frontmatter@1'
+```
+
+In browsers with [`esm.sh`][esmsh]:
+
+```html
+<script type="module">
+  import {frontmatterFromMarkdown, frontmatterToMarkdown} from 'https://esm.sh/mdast-util-frontmatter@1?bundle'
+</script>
+```
+
 ## Use
 
-Say we have the following file, `example.md`:
+Say our document `example.md` contains:
 
 ```markdown
 +++
@@ -43,16 +83,16 @@ title = "New Website"
 # Other markdown
 ```
 
-And our module, `example.js`, looks as follows:
+…and our module `example.js` looks as follows:
 
 ```js
-import fs from 'node:fs'
+import fs from 'node:fs/promises'
 import {fromMarkdown} from 'mdast-util-from-markdown'
 import {toMarkdown} from 'mdast-util-to-markdown'
 import {frontmatter} from 'micromark-extension-frontmatter'
 import {frontmatterFromMarkdown, frontmatterToMarkdown} from 'mdast-util-frontmatter'
 
-const doc = fs.readFileSync('example.md')
+const doc = await fs.readFile('example.md')
 
 const tree = fromMarkdown(doc, {
   extensions: [frontmatter(['yaml', 'toml'])],
@@ -66,7 +106,7 @@ const out = toMarkdown(tree, {extensions: [frontmatterToMarkdown(['yaml', 'toml'
 console.log(out)
 ```
 
-Now, running `node example` yields:
+…now running `node example.js` yields (positional info removed for brevity):
 
 ```js
 {
@@ -92,40 +132,132 @@ title = "New Website"
 
 ## API
 
-This package exports the following identifiers: `frontmatterFromMarkdown`,
+This package exports the identifiers `frontmatterFromMarkdown` and
 `frontmatterToMarkdown`.
 There is no default export.
 
-### `frontmatterFromMarkdown([options])`
+### `frontmatterFromMarkdown(options?)`
+
+Function that can be called to get an extension for
+[`mdast-util-from-markdown`][mdast-util-from-markdown].
+
+###### `options`
+
+Configuration (optional).
+Same as [`micromark-extension-frontmatter`][options].
+
+### `frontmatterToMarkdown(options?)`
+
+Function that can be called to get an extension for
+[`mdast-util-to-markdown`][mdast-util-to-markdown].
+
+###### `options`
+
+Configuration (optional).
+Same as [`micromark-extension-frontmatter`][options].
+
+## Syntax tree
+
+The following interfaces are added to **[mdast][]** by this utility.
+
+### Nodes
+
+> 👉 **Note**: other nodes are not enabled by default, but when passing options
+> to enable them, they work the same as YAML.
+
+#### `YAML`
+
+```idl
+interface YAML <: Literal {
+  type: "yaml"
+}
+```
+
+**YAML** ([**Literal**][dfn-literal]) represents a collection of metadata for
+the document in the YAML data serialisation language.
+
+**YAML** can be used where [**frontmatter**][dfn-frontmatter-content] content is
+expected.
+Its content is represented by its `value` field.
+
+For example, the following markdown:
+
+```markdown
+---
+foo: bar
+---
+```
+
+Yields:
+
+```js
+{type: 'yaml', value: 'foo: bar'}
+```
+
+### Content model
+
+#### `FrontmatterContent`
+
+```idl
+type FrontmatterContent = YAML
+```
+
+**Frontmatter** content represent out-of-band information about the document.
+
+If frontmatter is present, it must be limited to one node in the
+[*tree*][term-tree], and can only exist as a [*head*][term-head].
+
+#### `FlowContent` (frontmatter)
+
+```idl
+type FlowContentFrontmatter = FrontmatterContent | FlowContent
+```
+
+## Types
+
+This package is fully typed with [TypeScript][].
+It exports the additional types `Options`, `Matter`, and `Info`.
+
+The YAML node type is supported in `@types/mdast` by default.
+To add other node types, register them by adding them to
+`FrontmatterContentMap`:
 
-### `frontmatterToMarkdown([options])`
+```ts
+import type {Literal} from 'mdast'
 
-Support frontmatter (YAML, TOML, and more).
-These functions can be called with options and return extensions, respectively
-for [`mdast-util-from-markdown`][from-markdown] and
-[`mdast-util-to-markdown`][to-markdown].
+interface TOML extends Literal {
+  type: 'toml'
+}
+
+declare module 'mdast' {
+  interface FrontmatterContentMap {
+    // Allow using TOML nodes defined by `mdast-util-frontmatter`.
+    toml: TOML
+  }
+}
+```
 
-Options are the same as [`micromark-extension-frontmatter`][options].
+## Compatibility
+
+Projects maintained by the unified collective are compatible with all maintained
+versions of Node.js.
+As of now, that is Node.js 12.20+, 14.14+, and 16.0+.
+Our projects sometimes work with older versions, but this is not guaranteed.
+
+This plugin works with `mdast-util-from-markdown` version 1+ and
+`mdast-util-to-markdown` version 1+.
 
 ## Related
 
-*   [`remarkjs/remark`][remark]
-    — markdown processor powered by plugins
 *   [`remarkjs/remark-frontmatter`][remark-frontmatter]
     — remark plugin to support frontmatter
-*   [`micromark/micromark`][micromark]
-    — the smallest commonmark-compliant markdown parser that exists
 *   [`micromark/micromark-extension-frontmatter`][extension]
     — micromark extension to parse frontmatter
-*   [`syntax-tree/mdast-util-from-markdown`][from-markdown]
-    — mdast parser using `micromark` to create mdast from markdown
-*   [`syntax-tree/mdast-util-to-markdown`][to-markdown]
-    — mdast serializer to create markdown from mdast
 
 ## Contribute
 
-See [`contributing.md` in `syntax-tree/.github`][contributing] for ways to get
-started.
+See [`contributing.md`][contributing] in [`syntax-tree/.github`][health] for
+ways to get started.
 See [`support.md`][support] for ways to get help.
 
 This project has a [code of conduct][coc].
@@ -166,28 +298,40 @@ abide by its terms.
 
 [npm]: https://docs.npmjs.com/cli/install
 
+[esm]: https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c
+
+[esmsh]: https://esm.sh
+
+[typescript]: https://www.typescriptlang.org
+
 [license]: license
 
 [author]: https://wooorm.com
 
-[contributing]: https://github.com/syntax-tree/.github/blob/HEAD/contributing.md
+[health]: https://github.com/syntax-tree/.github
 
-[support]: https://github.com/syntax-tree/.github/blob/HEAD/support.md
+[contributing]: https://github.com/syntax-tree/.github/blob/main/contributing.md
 
-[coc]: https://github.com/syntax-tree/.github/blob/HEAD/code-of-conduct.md
+[support]: https://github.com/syntax-tree/.github/blob/main/support.md
 
-[mdast]: https://github.com/syntax-tree/mdast
+[coc]: https://github.com/syntax-tree/.github/blob/main/code-of-conduct.md
 
-[remark]: https://github.com/remarkjs/remark
+[mdast]: https://github.com/syntax-tree/mdast
 
 [remark-frontmatter]: https://github.com/remarkjs/remark-frontmatter
 
-[from-markdown]: https://github.com/syntax-tree/mdast-util-from-markdown
-
-[to-markdown]: https://github.com/syntax-tree/mdast-util-to-markdown
+[mdast-util-from-markdown]: https://github.com/syntax-tree/mdast-util-from-markdown
 
-[micromark]: https://github.com/micromark/micromark
+[mdast-util-to-markdown]: https://github.com/syntax-tree/mdast-util-to-markdown
 
 [extension]: https://github.com/micromark/micromark-extension-frontmatter
 
 [options]: https://github.com/micromark/micromark-extension-frontmatter#options
+
+[dfn-literal]: https://github.com/syntax-tree/mdast#literal
+
+[dfn-frontmatter-content]: #frontmattercontent
+
+[term-tree]: https://github.com/syntax-tree/unist#tree
+
+[term-head]: https://github.com/syntax-tree/unist#head