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@metalsmith/collections

A Metalsmith plugin that lets you group files together into ordered collections, like blog posts. That way you can loop over them to generate index pages, add 'next' and 'previous' links between them, and more

metalsmith: core plugin npm version ci: build code coverage license: MIT

Features

Installation

NPM:

npm install @metalsmith/collections

Yarn:

yarn add @metalsmith/collections

Usage

Pass options to @metalsmith/collections in the plugin chain:

import Metalsmith from 'metalsmith'
import markdown from '@metalsmith/markdown'
import collections from '@metalsmith/collections'
import { dirname } from 'path'

const __dirname = dirname(new URL(import.meta.url).pathname)

// defaults, only create collections based on file metadata
Metalsmith(__dirname)
  .use(markdown())
  .use(collections())

// defaults for a "news" collection, except pattern option
Metalsmith(__dirname)
  .use(markdown())
  .use(collections({
    news: { pattern: 'news/**/*.html' }
  }))

// explicit defaults for a "news" collection, except pattern option
Metalsmith(__dirname)
  .use(markdown())
  .use(collections({
    pattern: { pattern: 'news/**/*.html' },
    metadata: null,
    filterBy: () => true,
    sortBy: defaultSort,
    reverse: false,
    limit: Infinity,
    refer: true
  })

Note: all examples in the readme use the same collections definitions under Defining collections

Options

All options are optional

Defining collections

There are 2 ways to create collections & they can be used together:

Rendering collection items

Here is an example of using @metalsmith/layouts with jstransformer-handlebars to render the something-happened.md news item, with links to the next and previous news items (using refer: true options):

layouts/news.njk

<h1>{{ title }}</h1> {{!-- something-happened.md title --}}
<a href="/{{ collections.news.metadata.slug }}">Back to news</a> {{!-- news collection metadata.slug --}}
{{ contents | safe }}
<hr>
{{!-- previous & next are added by @metalsmith/collections --}}
{{#if previous}}
Read the previous news:
<a href="/{{ previous.path }}">{{ previous.title }}</a>
{{/if}}
{{#if next}}
Read the next news:
<a href="/{{ next.path }}">{{ next.title }}</a>
{{/if}}

Note: If you don't need the next and previous references, you can pass the option refer: false

Rendering collection index

All matched files are added to an array that is exposed as a key of metalsmith global metadata, for example the news collection would be accessible at Metalsmith.metadata().collections.news . Below is an example of how you could render an index page for the news collection:

layouts/news-index.hbs

<h1>{{ title }}</h1> {{!-- news collection metadata.title --}}
<p>{{ description }}</p> {{!-- news collection metadata.description --}}
<hr>
{{!-- previous & next are added by @metalsmith/collections --}}
{{#if collections.news.length }}
  <ul>
  {{#each collections.news}}
    <li>
      <h3><a href="/{{path}}">{{ title }}</a></h3>
      <p>{{ excerpt }}</p>
    </li>
  {{/each}}
  </ul>
{{/each}}
{{else}}
No news at the moment...
{{/if}}

Custom sorting, filtering and limiting

You could define an order property on a set of files and pass sortBy: "order" to @metalsmith/collections for example, or you could override the sort with a custom function (for example to do multi-level sorting). For instance, this function sorts the "subpages" collection by a numerical "index" property but places unindexed items last.

metalsmith.use(
  collections({
    subpages: {
      sortBy: function (a, b) {
        let aNum, bNum

        aNum = +a.index
        bNum = +b.index

        // Test for NaN
        if (aNum != aNum && bNum != bNum) return 0
        if (aNum != aNum) return 1
        if (bNum != bNum) return -1

        // Normal comparison, want lower numbers first
        if (aNum > bNum) return 1
        if (bNum > aNum) return -1
        return 0
      }
    }
  })
)

Note: the sortBy option also understands nested keypaths, e.g. display.order

The filterBy function is passed a single argument which corresponds to each file's metadata. You can use the metadata to perform comparisons or carry out other decision-making logic. If the function you supply evaluates to true, the file will be added to the collection. If it evaluates to false, the file will not be added. The filterBy function below could work for a collection named thisYearsNews as it would filter out all the items that are older than this year:

function filterBy(file) {
  const today = new Date()
  const pubdate = new Date(file.pubdate)
  return pubdate.getFullYear() === today.getFullYear()
}

Add a limit option to a collection config, for example to separate recent articles from archives:

metalsmith.use(
  collections({
    recentArticles: {
      pattern: 'articles/**/*.html',
      sortBy: 'date',
      limit: 10
    },
    archives: {
      pattern: 'archives/**/*.html',
      sortBy: 'date'
    }
  })
)

Note: the collection is first sorted, reversed, filtered, and then limited, if applicable.

Collection Metadata

Additional metadata can be added to the collection object:

metalsmith.use(
  collections({
    news: {
      metadata: {
        title: 'Latest news',
        description: 'All the latest in politics & world news',
        slug: 'news'
      }
    }
  })
)

Collection metadata can be loaded from a json or yaml file (path relative to Metalsmith.directory()):

metalsmith.use(
  collections({
    articles: {
      sortBy: 'date',
      reverse: true,
      metadata: 'path/to/file.json'
    }
  })
)

Debug

To log debug output, set the DEBUG environment variable to @metalsmith/collections:

Linux/Mac:

DEBUG=@metalsmith/collections

Windows:

set "DEBUG=@metalsmith/collections"

CLI Usage

Add the @metalsmith/collections key to your metalsmith.json plugins key:

{
  "plugins": [
    {
      "@metalsmith/collections": {
        "articles": {
          "sortBy": "date",
          "reverse": true
        }
      }
    }
  ]
}

License

MIT