Jekyll Data Pages Generator

Jekyll allows data to be specified in YAML or JSON format in the _data dir.

If the data is an array, it is straightforward to build an index page, containing all records, using a Liquid loop. In some occasions, however, you also want to generate one page per record. Consider, e.g., a list of team members, for which you want to generate an individual page for each member.

This generator allows one to specify data files for which we want to generate one page per record.

Among the advantages:

• general purpose: it works with any array of data: people, projects, events, ... you name it
• it manages multiple data sources in the same website

Installation

Download data_page_generator.rb and put it in the _plugins directory of your website.

Usage

• Specify in _config.yml the data files for which you want individual page to be generated.
• Launch Jekyll

The specification in config.yml is as follows:

page_gen:
  - index_files: <<true or false>
    data: <<name of the data>>
    template: <<name of the template to use to generate the page>>
    name: <<field used to generate the filename>>
    dir: <<directory in which files are to be generated>>
    extension: <<extension used to generate the filename>>
    filter: <<property to filter data records by>>
  - ...

where:

index_files : specifies if we want to generate named folders (true) or not (false) for the current set of data. Optional: if specified, it overrides the value of the global declaration page_gen-dirs.

data : is the name of the data file to read (YAML, Json, or CSV). Use the full path if your data is structured in a hierarchy. For instance: hierarchy.people will loop over a variable people in the _data/hierarchy.yml file

name : is the name of a field in data which contains a unique identifier that can be used to generate a filename

template : is the name of a template to generate the pages (it defaults to the value of data + ".html"). Optional: if not set, the generator uses the value of the data field

dir : is the directory where pages are generated (it defaults to the value of data). Optional: if not specified, the generator uses the value of the data field.

extension : is the extension of the generated file. Optional: if not specified, the generator uses "html" extension.

filter : is a property of each data record that must return a true-ish value for the record to be included in the list of files to be generated. Optional: if not specified, all records from the dataset are included (see also filter_condition).

filter_condition : is a string containing a Ruby expression which evaluates to a true-ish value. The condition can reference fields of the data being read using the record hash (e.g., record['author'] == 'George Orwell'). Optional: if not specified, all records from the dataset are included (see also filter).

Notes

• More than one data source can be specified: the generator iterates over each element of the data_gen array.
• The same data structure can be referenced different times, maybe with different target directories. This is useful to group pages in different directories, using filter_condition.

A liquid tag is also made available to generate a link to a given page. For instance:

   {{ page_name | datapage_url: dir }}

generates a link to page_name in dir.

Named Folders

By default the plugin generates one filename per record. If you prefer to generate named folders, set the page_gen-dirs to true in config.yml.

Example

1. You have an members.yml file stored in the _data directory of your Jekyll website, with the following content:

   • name: adolfo villafiorita bio: long bio goes here
   • name: pietro molini bio: another long bio
   • name: aaron ciaghi bio: another very long bio

Alternatively, you could have members.json file stored in the _data directory with the following content and the example would work the same:

[
  {
    "name": "adolfo villafiorita",
    "bio": "long bio goes here"
  },
  {
    "name": "pietro molini",
    "bio": "another long bio"
  },
  {
    "name": "aaron ciaghi",
    "bio": "another very long bio"
  }
]

2. There is a profile.html file stored in the _layouts directory:

<h1>{{page.name}}</h1>

{{page.bio}}

3. _config.yml contains the following:

   page_gen:

   • data: 'members' template: 'profile' name: 'name' dir: 'people'

Then, when building the site, this generator will create a directory people containing, for each record in members.yml, a file with the record data formatted according to the profile.html layout. The record used to generate the filename of each page is name, sanitized.

$ cd example
$ jekyll build
$ cat _site/people/adolfo-villafiorita.html
<h1>Adolfo Villafiorita</h1>

long bio goes here

Check the example directory for a live demo. (Notice that the ruby file in _plugins is a symbolic link; you might have to remove the link and manually copy the ruby file in the _plugins directory, if symbolic links do not work in your system.)

Filters

There are three different ways which you can use to show only the relevant records of a data structure in your website:

Do not link uninteresting pages

Generate pages for all records (relevant and not), but link only the interesting pages.

The uninteresting pages will still get generated but will not be easily accessible. A visitor has to guess the URL to access them. This is more of a workaround, rather than a solution.

This is shown in the books.md file, in the section "Books I have read".

The filter is applied to the links to tha generated pages. Pages will still be generated for all books, but only those for which book.read is true will be easily accessible (since only these have an explicit link in our website).

Use the filter condition

Use the filter property.

In this case, all records in your data structure should have a boolean field, let us say, publish. Pages will be generated only for those records in which the publish field is true(-ish).

Consider the following declaration in _config.yml:

- data: 'books'
  template: 'book'
  name: 'title'
  dir: 'books-i-have-read'
  filter: read  # read is a boolean value in the YML file

In this case, a page will be generated only for the books in which the field read is true.

Use the filter_condition condition

Use the filter_condition property.

The field should contain a string which evaluates to a boolean expression. The string may reference fields of the data structure using the record[<field_name>] notation, like, for instance in record['author'] == 'George Orwell'.

In this case pages will be generated only for the records satisfying the evaluation of the filter_condition.

Example 1. Consider the following declaration in _config.yml:

- data: 'books'
  template: 'book'
  name: 'title'
  dir: 'books-i-have-not-read'
  filter_condition: "record['read'] == false"

that allows me to generate a list of the books I have not read. The filter keyword, in this case, is no good, since I need to test for falsity (read has to be false).

The filter condition allows to select only those records in which record['read'] is false.

Remark If you want to filter on nested fields, use multiple []. For instance:

filter_condition: "record['did-i']['read'] == false"

works with the following data structure:

- author: Harper Lee
  title: To Kill a Mockingbird
  did-i:
    read: no
  rating: 4.26
  year: 1960
  position: 1

Example 2. Consider the following declaration in _config.yml:

- data: 'books'
  template: 'book'
  name: 'title'
  dir: 'books-by-orwell'
  filter_condition: "record['author'] == 'George Orwell'"

In this case, I am testing the author field and generating pages only for the books by George Orwell.

As a final consideration, filter_condition allows one to deploy pages in different directories according to specific properties.

Consider the following example:

- data: 'books'
  template: 'book'
  name: 'title'
  dir: 'books-read'
  filter_condition: "record['read'] == true"
- data: 'books'
  template: 'book'
  name: 'title'
  dir: 'books-to-read'
  filter_condition: "record['read'] == false"

which splits the book data structure in two different folders, according to the value of the read flag.

Of course, such an approach makes sense only for variables with a limited number of values, since one needs to explicitly specify in _config.yml conditions and target directories.

Compatibility

Run with Jekyll 3.1.6 and Jekyll 3.6.2, it should also work with previous versions of Jekyll. Try with the included example and open an issue if you find any compatibility issue.

Author and Contributors

Adolfo Villafiorita with contributions from various authors.

Known Bugs

Some known bugs and an unknown number of unknown bugs.

(See the open issues for the known bugs.)

License

Distributed under the terms of the MIT License.