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README.org

README

Jekyll Data Pages Generator

Jekyll allows data to be specified in YAML, CSV, and 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

Option 1. Add =gem “jekyll-datapage-generator”= to your project Gemfile and then load it as a plugin in the configuration:

plugins:
  - jekyll-datapage-generator

(See https://jekyllrb.com/docs/plugins/installation/ for more details.)

Option 2. Download jekyll-datapage-generator.rb and put it in the _plugins directory of your website. Remember to delete older versions of the source file from the =_plugins= directory or you might run into errors.

Quick Start

Read the Example section or the included example to get started quickly.

Usage

  • Specify in _config.yml the data files for which you want to generate individual pages.
  • Launch Jekyll

The specification in config.yml looks like:

page_gen-dirs: [true|false]

page_gen:
- data: [name of a data set in _data]
  template: [name of template in _layouts: will be used to render pages]
  dir: [directory where filenames will be generated]
  index_files: [true|false]
  name: [field used to generate the filename]
  name_expr: [a Ruby expression to generate the filename (alternative to name)]
  title: [field used to generate the page title]
  title_expr: [a Ruby expression to generate the filename (alternative to title)]
  extension: [extension used to generate the filename]
  filter: [property to filter data records by]
  filter_condition: [a Ruby expression to filter data]
  
[another set of data, if you want ...]

where:

  • page_gen-dirs specifies whether we want to generate named folders (true) or not (false) for all generated data.
  • page_gen is an array specifying a data for which individual pages have to be generated.

Each entry in page_gen can (in some cases must) contain the following fields:

  • 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 the variable people in the _data/hierarchy.yml file.
  • template is the name of a template used to layout data in the page. Optional, it defaults to the value =data= if not specified.
  • 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.
  • name is the name of a field in the data used to generate a filename. You need to ensure values in the chosen field are unique, or some files will get overwritten.
  • name_expr is an optional Ruby expression used to generate a filename. The expression can reference fields of the data being read using the record hash (e.g., record['first_name'] + "_" + record['last_name']; see the documentation of filter_condition for more details.) Optional: used in alternative to =name=. If set it overrides =name=
  • index_files specifies whether 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=.
  • title is the name of a field in data which is used for the page title. Optional: if not specified, the generator uses the filename.
  • title_expr is an optional Ruby expression used to generate the page title. The expression can reference fields of the data being read using the record hash (e.g., record['first_name'] + "_" + record['last_name']). Optional, but if set, it overrides =title=.
  • extension is the extension of the generated files. Optional: if not specified, the generator uses =html= extension.
  • page_data_prefix is the prefix used to output the page data. Data read from each record is made available in the page so that it can be accessed using liquid tags. In some cases, however, there might be clashes with existing tags. page_data_prefix can be used to prefix all data read from records and avoid the problem mentioned above. Optional: if not specified, no prefix is used.
  • 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. See Filtering Data, below, for more details. 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’=). See Filtering Data, below, for more details. Optional:* if not specified, all records from the dataset are included (see also =filter=).
  • debug is a Boolean value specifying whether the plugin will output information about the configuration and data read. Optional:* if not specified, no debug information is outputted.

Note. 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.

Filtering Data

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.

Generating Filename with an Expression

You can generate filenames with an expression, by replacing name with name_expr. For example, if you have data in a .yml file that looks like this:

- first_name: adolfo
  last_name: villafiorita
  bio: long bio goes here
- first_name: pietro
  last_name: molini
  bio: another long bio
- first_name: aaron
  last_name: ciaghi
  bio: another very long bio

Your _config.yml could contain the following:

page_gen:
  - data: 'members'
    template: 'profile'
    name_expr: record['first_name'] + "_" + record['last_name']
    dir: 'people'

Example

  1. You have a members.yml file in the _data directory, 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 a members.json (or a members.csv 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"
  }
]
  1. There is a profile.html file in the _layouts directory:
<h1>{{page.name}}</h1>

{{page.bio}}
  1. _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.)

Change Log

See the CHANGELOG file.

Compatibility

Run successfully at least once with the following Jekyll versions: 4.0.1, 3.8.5, 3.6.2, 3.1.6. Try with the included example and open an issue if you find any compatibility issue.

Author and Contributors

Adolfo Villafiorita with several excellent 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.

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