Templates

We use PyJade as a Jinja extension. Templates with the extension .j2.jade are passed to PyJade and converted to a Jinja template.

Our templates mostly support the syntax of Pug which was called Jade before. Instead of Javascript, pieces of code in templates are interpreted as Jinja code. Keep that in mind when reading the language reference for Pug. As a basic rule, keep complicated logic away from templates and use Python code from the cell associated with a template. Reading existing templates and following their style is a good idea.

HTML Tags and Attributes

By default, text at the start of a line (or after only white space) represents an HTML tag. Indented tags are nested, creating the tree structure of HTML.

ul
  li Item A
  li Item B
  li Item C

Tag attributes look similar to HTML, with optional commas between them. Simple values are strings with quotes:

a(href='//example.com', target='_blank') Example

Class and ID Literal

In addition to using the class attribute like in HTML, classes can be added to tags with the .classname syntax:

a.button.button-primary
<a class="button button-primary"></a>

For divs, you can skip writing div and just use a class literal:

.content
<div class="content"></div>

ID literals follow the same rules start with a #.

Values from Expressions

Attribute values support Jinja expressions:

a.link(href=example_url, class=("extra" if options.extra else "")) Example

Adds “extra” to class attribute only if options.extra is true:

<a class="link extra">Example</a>

Boolean Attributes

input(type='checkbox' checked) [x]
|
input(type='checkbox' checked=true) [x]
|
input(type='checkbox' checked=false) []

Differences to Pug

  • Jinja expressions instead of Javascript
  • no multiline attributes
  • no special handling of class and style attributes
  • no support for &attributes syntax

Code

Buffered (With Output)

= is used to produce output from a Jinja expression. Pug calls this buffered code. This works like {{ }} in Jinja. For security, output is automatically escaped by Jinja.

p
  = 'This code is <escaped>!'

For translations, gettext with _ as alias and ngettext from Babel are available in all templates.

Templates that are used by a Cell have access to all methods of the Cell that don’t start with _. Methods that only have the self argument are automatically turned into cached properties and can be used without ().

a(href=index_url)= _('back_to_index')

This uses the return value of a cell method def index_url(self): ... as link target and the translation for ‘back_to_index’ as link text.

Warning

Don’t put a space before the =!

Often it’s nicer to put the code in the next line which has the same effect as the last example:

a(href=index_url)
  = _('back_to_index')

Unescaped HTML

To output HTML without escaping, wrap the string in Python code with Markup() from markupsafe.

Unbuffered

- can be used to run Jinja code directly, without output. Pug calls this unbuffered code. This works like {% %} in Jinja.

We use it for layout extension and blocks on the Jinja level but this may go away in the future.

- extends "ekklesia/layout.j2.jade"
- block content
  .content

In Jinja syntax, that block looks like this:

{% block content %}
<div class="content"></div>
{% end block %}

Try to avoid putting code in templates, most of the time there are better ways to express things. Logic should be implemented in a Cell method or code called by a cell method.

Conditionals

Conditionals can check values for “truthyness” like in Jinja/Python:

if output
  = output

Writes output only if output is truthy (not empty string or not None, for example).

If … else is also supported:

if options.show_full_output
  = full_output
else
  = short_output

Plain Text

Text after a tag is just rendered as plain text:

p Some Text

You won’t need that often because we want to translate most of the strings.

Use a pipe to put plain text on a separate line. Whitespace after the pipe is included in the output.

p
  |Some Text
  | More Text

Whitespace at the end of the line is also rendered! This should be avoided because many editors will strip trailing whitespace and change semantics of the template.

<p>Some Text More Text</p>

Mixing Code with Text

Let’s say we want to output two values separated by a space:

p
  = first_part
  |&nbsp;
  = second_part

Iteration

Use for to iterate over a sequence:

ul
  for item in items
    = li.list-item= item.text

Comments

// comment which is rendered to a HTML comment

//- comment which is just for the template, not rendered to HTML

Code Style

  • Always use 2 spaces for indentation. Do not mix!
  • Line length should not exceed 120, but sometimes it’s neccessary to write longer lines.
  • Avoid putting = output directly after a HTML tag, especially when it has multiple attributes. Put it on a indented line instead.