An advanced pagination tool for jekyll

I must apologize to those who have downloaded 1.0.0 to 1.0.2 version of this plugin. I should have tested it in more complicated situations before publishing it.

Also I'd like to apologize for the irresponsible pushes to RubyGems. I am new to Ruby and got overenthusiastic to have my own gem published.

I really would like this plugin to be useful and hope everyone enjoys it.

First you must install jekyll-pagination-task. It can be done by

gem install jekyll-pagination-task

or download the source code and compile it locally:

git clone https://github.com/emiapwil/jekyll-pagination-task
cd jekyll-pagination-task
gem build jekyll-pagination-task.gemsepc
gem install jekyll-pagination-task-{VERSION}.gem

Of course, you can just download the code and put lib/jekyll-pagination-task/pagination_task.rb to the _plugins/ folder of your jekyll site.

After the installation you can put the following line in the _plugins/ext.rb to make jekyll aware of its presence. If the ruby source file is put in _plugins, however, you can skip this step.

require "jekyll-pagination-task"

Then it is also required to add the following lines in _config.yml:

pagination_task:
  page_per_pager: 7
  format: /:dir/:name/:Num
  filter_class: Jekyll::PaginationTask::DefaultPaginationFilter
  post_only: true

The first line is crucial since it indicates that jekyll-pagination-task plugin will be enabled. The other three lines are all optional:

• page_per_pager: how many pages should be include in one pager. The default value is 7.
• format: how the url of the generated pagers should look like. The default value is /:dir/:name/:Num. There are currently 4 macros:
  • :dir: it will be replaced by the path to the template page;
  • :name: it will be replaced by the basename of the template page;
  • :num: it will be replaced by the index of the generated page;
  • :Num: same as :num expect that 1 is replaced by an empty string.
• filter_class: which class to use as the filter for pages. The default value is Jekyll::PaginationTask::DefaultPaginationFilter.
• post_only: only paginate the posts, the default value is true. If set to false, the pages will be paginated as well.

Unlike jekyll-paginate, this plugin identify template pages by checking whether the attribute paginate is set to true in a page. To make things more flexible, some other optional attributes can be set as well. These configurations are demonstrated in the following example:

---
paginate: true
page_per_pager: 8
pagination_format: /posts/:Num
filter_class: Jekyll::PaginationTask::DefaultPaginationFilter
pagination_filter:
  - ['layout', 'is', 'post']
  - ['category', 'all', ['test', 'ruby']]
---

• paginate: indicates that this page is a template.
• page_per_pager: same as page_per_pager in _config.yml.
• pagination_format: same as format in _config.yml.
• filter_class: same as filter_class in _config.yml.
• pagination_filter: this is used to store parameters for Jekyll::PaginationTask::DefaultPaginationFilter, each element of it will have the form of [$ATTR, $RELATION, $PARAMETER]. Then attribute $ATTR of the template page will be checked against $A_LIST_OF_VALUES and the pages that satisfy all these conditions will be set as the pager's posts (this is for compatibility with jekyll-paginate). There are currently 8 relations supported:
  • all: true if the attribute $ATTR contains all values from $PARAMETER and otherwise false;
  • any: true if the attribute $ATTR contains any of the values from $PARAMETER and otherwise false;
  • only: true if the attribute $ATTR contains values only from $PARAMETER and otherwise false;
  • none: true if the attribute $ATTR contains no values from $PARAMETER and otherwise false;
  • is: true if $ATTR equals $PARAMETER and false otherwise
  • is_not: true if $ATTR doesn't equal $PARAMETER and false otherwise
  • in: true if $ATTR is a member of $PARAMETER
  • not_in: true if $ATTR is not a member of $PARAMETER

It is notable that the types of $ATTR and $PARAMETER are also indicated in these relationships and I think they can cover most cases. If the default filter still fails to meet the needs, you can always develop your own filter class and point to it by setting the filter_class option.

Assuming the full name of the template page is demo/post.md which selects 45 posts using the frontmatter above. The following files will be generated: /demo/post/index.html, /demo/post/2/index.html, ..., and /demo/post/6/index.html.

If we have another file named demo/post7.md which uses the same frontmatter expect the page_per_pager line, it will use the configuration in _config.yml and 7 pages will be generated with prefix /demo/post7/ instead of /demo/post/.

If we modify the pagination_format in this demo/post7.md file to /home/test/:Num, then the pages will be generated in /home/test/ folder rather than /demo/post7.

Here is a quick introduction to the implementation of jekyll-pagination-task:

• selects pages with paginate set to true as templates
• for each tempalte, construct the filter with site and the template
• selects pages that satisfies the filter
• create PTPager, which is derived from Jekyll::Pager and can set up the correct url for generated pagination pages. Then the generated pager pages are appended to site.pages

• Infinite page_per_pager.
• Structed options in the frontmatter.
• Customized Sorter support. Currently the posts are not sorted.

I'm new to Ruby and this package is not fully tested, so there might be many bugs...

The reason is that Jekyll::Page will generate the url once url is called and store it in @url which is not accessible thus not modifiable. One workaround is to hack the Jekyll package and add the :url to attr_accesssor in Jekyll::Page and then add one more line in create_pager just before it returns:

instance.url = nil # reset the url

Update: the hack is not necessary now since most plugins are unlikely to touch these template files and the problem occurred earlier is caused by a call to dir in calculating the pagination path within this plugin. It is fixed in a recent commit.