Liquid::Pry
“Pry is a runtime developer console with powerful introspection capabilities.” — Pry home page
Liquid::Pry brings Pry to Liquid templates and to Jekyll-powered sites.
Installation
Without Jekyll
Add following to the Gemfile:
gem "liquid-pry"
With Jekyll
If you want to integrate Liquid::Pry with Jekyll, it’s probably the easiest
to add following to the Gemfile, so that Jekyll will automatically load and
enable Liquid::Pry:
group :jekyll_plugins do gem "liquid-pry" end
For other options, read Jekyll documentation.
Usage
This gem provides a Liquid filter and a Liquid tag.
Filter
The pry filter hooks Pry into filter chain in a Liquid template, helping user
to debug Jekyll’s front matter or any other data available in given template.
For example following could be used to debug page.title:
You are on page {{ page.title | pry }}.
When Liquid renderer encounters pry filter, then Pry console is launched.
A convenience local variable named input is defined, which contains filter
input (value of page.title in above example), allowing site developer to
inspect or alter that value. Another local variable context provides access
to rendering context.
The filter returns its input, hence it does not affect rendered page. Also, it
can be placed anywhere in the filter chain, not necessarily at the end.
For example, in a following example pry filter is placed before upcase,
allowing user to inspect page.title value before the upcase filter is
applied.
You are on page {{ page.title | pry | upcase }}.
However, if user modify the value of input variable, then modified version is
returned. This may be used for experimenting.
The pry filter is typically more useful than the pry tag, especially for
novice users.
Tag
The pry tag interrupts Liquid rendering, allowing user to inspect or modify
the rendering context. For example:
{% pry %}
When Liquid renderer encounters pry tag, then Pry console is launched
and rendering context is available via context local variable.
Using with once option
If pry tag is supplied with once option, then Pry console is launched only
for the first time that tag is encountered on given page. In following example:
{% for product in collection.products %}
{% pry once %}
{{ product.title }}
{% endfor %}
Pry will be launched only once, no matter if collection.products contains one
item or a hundred.
Still, in following example Pry will be launched twice, because pry tag is
placed that many times in the template:
{% pry once %}
{% pry once %}
Using Pry console
See Pry documentation.
Credits
This gem is developed, maintained and funded by Ribose Inc.
License
The gem is available as open source under the terms of the MIT License.
See also
This gem is tiny but quite comprehensive. However, there are some other ones you may want to try:
-
jekyll-liquid-debug (a very different approach)
-
octopress-debugger (seems unmaintained as of Jan 2021)