Templates#

Templates in Liara are used to style content. There are two parts to every template, the first is the definition which describes which template should get applied to which URL, and the template execution environment which provides the content that will be consumed by the template.

Definition#

Templates are defined using a template definition, which must contain at least two fields:

  • backend selects the template engine. This must be one of:

    • jinja2: Uses Jinja2. This is the default.

    • mako: Uses Mako

  • paths provides a dictionary containing key-value pairs. See path patterns for more details.

  • backend_options contains a mapping of options to be passed to the backend. For example, for Jinja2, if you want to keep the trailing newline, you’d set:

    backend_options:
  jinja2:
    keep_trailing_newline: true

    Currently, only the Jinja2 backend has options that can be set this way. The default options that are set to enabled are trim_blocks and lstrip_blocks. You can set any Jinja2 option that doesn’t expect a Python object. Additionally, enable_async can’t be toggled.

A very basic template could be defined as following:

backend: jinja2
paths:
  "/*": "default.jinja"

This would process any page using the default.jinja template.

Template definitions also support the following fields:

  • static_directory specifies static files which will be deployed to the output. This can be used for images etc.

  • resource_directory specifies resource files to be deployed, for instance SASS files. See Resources for more details.

  • image_thumbnail_sizes: Replaced by image_thumbnails.sizes, see below.

    Deprecated since version 2.4.1.

  • image_thumbnails is a dictionary used to configure image thumbnails:

    image_thumbnails:
 sizes:
   thumbnail-md: {width: 640}
   thumbnail-xs: {width: 320, exclude: "*.preview.*"}
   hero: {width: 960, include: "*.hero.*"}
 formats:
   - original
   - webp

    This definition will create three kinds of thumbnails. The first entry will resize any static image file (from the template or the site itself) to a maximum width of 640 pixels. The thumbnail will be stored using the same file path as the original, but with thumbnail-md added to the suffix. For instance, an input file named foo.png with width 800 would be resized to foo.thumbnail-md.png with a width of 640. Files which are below the size will get copied, so it’s always safe to use the .thumbnail-md suffix.

    Additionally, it will create files with a thumbnail-xs suffix for all files which don’t match the exclude pattern, and hero thumbnails for all files with do match the include pattern. This is useful to exclude manually created thumbnails, or only create thumbnails for files which are particularly large. include and exclude are mutually exclusive, only one can be set per thumbnail size.

    formats is a list of formats to use for the thumbnails. original means the original format is used (determined from the file extension). Additional supported formats are: JPG, PNG and WEBP.

    New in version 2.4.1: formats and sizes were added.

    New in version 2.5.0: exclude and include were added.

Note

There is nothing special about thumbnail-md in the example above – any suffix can be used, and multiple suffixes are supported (for example, thumb-1x and thumb-2x for normal and high density screens.)

Authoring Templates#

Templates get applied to DocumentNode and IndexNode instances only (which are referred to as “pages” in the context of a template.) Inside a template, a few global variables are pre-populated to provide access to the site and page content. Note that the content of other nodes cannot be referenced inside a template (as the order in which they get executed is unspecified), however, metadata of other nodes is available and can be used.

  • page references the current node, in form of a Page instance.

  • node provides access to the current node directly, which will point to a Node instance.

  • site provides access to the site in form of the SiteTemplateProxy object.

  • build_context provides access to the BuildContext, which provides information about the current build like the last-modified-date of the source file.

In most cases, templates should only use the page reference as it’s rarely useful to directly access the underlying node instances. One use case for accessing the nodes is for example to create a listing of all images in a folder, as images are instances of StaticNode.

Path patterns#

The paths used for template matching are using a syntax very similar to filesystem globs, with * being the only wildcard character supported. Perfect matches take precedence over wildcard matches. That is, if there are two path patterns /foo/* and /foo/, and they are matched against /foo/, both match but /foo/ gets selected as it’s a perfect match.

The patterns have two additional tie-breaker rules implemented if multiple rules apply to the same template:

  • If two rules have the same score, the longer rule wins, as it’s assumed to be more specific. For instance, if you have a rule /en* and /*, and you match /en, then both match, but because /en* is longer it gets selected.

  • If rules have the same length and match the same URL, the first matching rule is used. I.e. if you specify /e* and /*n to match /en, whichever rule came first in the rule set wins.

Additionally, template path patterns allow a query string to restrict the search to specific types. For instance, /foo/*?kind=document will match all DocumentNode below /foo/, but will ignore other node types. The nodes types that can be selected using this method are document for DocumentNode instances and index for IndexNode instances.