Lektor Tags Plugin

Introduction

This plugin implements tagging for your site. For each of your tags, it builds a page displaying a list of items that have that tag. This can be used for standard tag-based blog navigation. With this plugin you can give any number of tags to any blog posts, and a page will be created for each tag.

For example, if your site has blog posts in your content/blog directory tagged with coffee and tea:

name: First Post
---
tags:

coffee
tea

The lektor-tags plugin builds pages at these URLs:

• /blog/tag/coffee/
• /blog/tag/tea/

Each page can list all the posts with that tag.

Installation

Add lektor-tags to your project from command line:

lektor plugins add lektor-tags

See the Lektor documentation for more instructions on installing plugins.

Overview

Say you have a "blog-post" model like this:

[model]
name = Blog Post

[fields.tags]
type = strings

Make a blog-post.html template that includes:

{% if this.tags %}
  <ul>
    {% for t in this.tags -%}
      <li>
        <a href="https://github.com/lektor/lektor-tags/blob/master/{{ ('/blog@tag/' ~ t)|url }}">
          All posts tagged {{ t }}
        </a>
      </li>
    {% endfor %}
  </ul>
{% endif %}

This expression in the template generates a source path for each of the blog post's tags:

'/blog@tag/' ~ t

Then if the tag is "my-tag", the expression renders a source path like:

/blog/tag/my-tag

A Lektor source path becomes an actual URL using the url filter. So the template generates URLs to tag pages like:

<a href="https://github.com/lektor/lektor-tags/blob/master/{{ ('/blog@tag/' ~ t)|url }}"></a>

This uses the source path expression from before, but pipes it through url to generate an actual link from the blog post to a tag page.

Configuration

Set these options in configs/tags.ini:

parent

Required. The source path of the tag pages' parent page. For example:

parent = /blog

Then tag pages' source paths are like:

/blog/tag/my-tag

You can specify the root as the parent:

parent = /

items

A query for all items on the page for one tag. You can use the variables site and tag. The template's this variable has a parent attribute. The default query is:

items = this.parent.children.filter(F.tags.contains(tag))

You can sort and filter with any expression:

items = this.parent.children.filter(F.tags.contains(tag) and F.status == 'published').order_by('-pub_date')

If the parent page has a pagination query you may want to use it for tagged pages:

items = this.parent.pagination.items.filter(F.tags.contains(tag))

See the Lektor documentation for queries.

tags_field

The name of the field in your model that contains tags. Defaults to tags. The field should be of type strings. See the Lektor documentation for the strings type.

For example, if your model is like:

[fields.labels]
type = strings

Then add this to tags.ini:

tags_field = labels

template

The template for the page that lists all posts with a certain tag. The template's this variable has attributes tag and items. An example template:

<h1>Tag: {{ this.tag }}</h1>
<h1>Items:</h1>
<ul>
  {% for i in this.items %}
    <li><a href="https://github.com/lektor/lektor-tags/blob/master/{{ i|url }}">{{ i._id }}</a></li>
  {% else %}
    <li><em>No items.</em></li>
  {% endfor %}
</ul>

Save a file like this to your project's templates/tags.html. If you name the file something different, like label.html, add this line to tags.ini:

template = label.html

The plugin provides a default template if you don't specify one.

url_path

An expression for the location of each tag page. You can use the variables site and tag. The this variable is a page with attributes parent and items. The default expression is:

url_path = {{ this.parent.url_path }}tag/{{ tag }}

This expression generates URLs like /blog/tag/coffee.

ignore_missing

Default false. To set true, add this line to tags.ini:

ignore_missing = true

This allows URLs to missing tag pages to be silently replaced with "". The example use case is if your blog-post.html template includes a statement like:

{% for t in this.tags -%}
  <a href="https://github.com/lektor/lektor-tags/blob/master/{{ ('/blog@tag/' ~ t)|url }}">{{ t }}</a>
{% endfor %}

If a blog post draft is not discoverable, and it has any new tags used by no published blog posts, then those tag pages do not yet exist. Turn on ignore_missing to allow such drafts to be built. The tag-page URL path will be the empty string "", until the draft is published and the tag page is created.

tags

Advanced configuration. An expression for the set of tags. Note that this expression is also useful in a template to get a list of all tags. The default expression is:

tags = parent.children.distinct("tags")

If you set tags_field to a different field name than "tags", the default expression uses your custom field name. For example if you have this line in tags.ini:

tags_field = labels

Then the default value of tags is:

tags = parent.children.distinct("labels")

You can use any template expression. For example, if your items have a "published" boolean field, you can select tags of published items:

tags = parent.children.filter(F.published).distinct("tags")

Or even list your tags manually:

tags = ["tag1", "tag2"]

See the Lektor documentation for queries.

Tags are always deduplicated. Tags are sorted in the order listed in the contents.lr / admin, allowing you to control their order manually. Since {{ tags }} simply returns a list, you can always apply any Jinja2 filter on that list such as sort, slice, or rejectattr.

Tag cloud & tag weights

This plugin won't automatically build a tag cloud, but it provides the tools to build it.

The Jinja2 context has a tagweights() function, which returns a dictionary that maps tags to their weight using several attributes or functions. Here are those attributes and functions, with examples of how they can be used in a template.

Unused tags are ignored.

TL;DR Which weight function should I use?

• To get the number of pages tagged by each tag, use count.
• To map tags to numbers, use log(lower, upper).
• To map tags to everything else, use loggroup(list).

count — Number of pages tagged with this tag

This is the basic weight, used as a base for the following tags.

Example: Tags (with tag count) sorted by tag count (most used first)

<ul>
{% for tag, weight in (tagweights() | dictsort(by='value', reverse=true)) %}
    <li>{{ tag }} ({{ weight.count }} articles).</li>
{% endfor %}
</ul>

linear — Tags are mapped with a number between lower and upper.

The less used tag is mapped lower, the most used tag is mapped upper (lower and upper can be equal, upper can be smaller than lower).

Mapping is done using a linear function.

The result is a float: you might want to convert them to integers first (see example for log).

Unless you know what you are doing, you should use log instead.

log — Logarithm of tag counts are mapped with a number between lower and upper.

The less used tag is mapped lower, the most used tag is mapped upper (lower and upper can be equal, upper can be smaller than lower).

Mapping is done using a linear function over the logarithm of tag counts.

The result is a float: you might want to convert them to integers first (see example).

Example: Most used tag is twice as big as least used tag

{% for tag, weight in tagweights()|dictsort %}
<a
    href="https://github.com/lektor/lektor-tags/blob/master/{{ ('/blog@tag/' ~ tag)|url }}"
    style="font-size: {{ weight.log(100, 200)|round|int }}%;"
    >
        {{ tag }}
    </a>
{% endfor %}

lineargroup — Map each tag with an item of the list given in argument

The less used tag is mapped with the first item, the most used tag is mapped with the last item.

Mapping is done using a linear function.

Unless you know what you are doing, you should use loggroup instead.

loggroup — Logarithm of tag counts are mapped with an item of the list given in argument

The less used tag is mapped with the first item, the most used tag is mapped with the last item.

Mapping is done using a linear function over the logarithm of tag counts.

Example: Tags are given CSS classes tagcloud-tiny, tagcloud-small, etc.

{% for tag, weight in tagweights()|dictsort %}
<a
    href="https://github.com/lektor/lektor-tags/blob/master/{{ ('/blog@tag/' ~ tag)|url }}"
    class="tagcloud-{{ weight.loggroup(["tiny", "small", "normal", "big", "large"]) }}"
    >
        {{ tag }}
    </a>
{% endfor %}