liquid - Liquid template engine for Crystal

Liquid templating language: http://shopify.github.io/liquid/

This is a fork of TechMagister/liquid.cr, which was moving too slowly for my needs. I'm open to merging back at some point, and will do my best to maintain compatibility, but for the foreseeable future (through 2019), this fork may be unstable and/or add breaking changes here and there. Still, it includes many useful improvements, so please give it a try and report any issues you find.

Installation

Add this to your application's shard.yml:

dependencies:
  liquid:
    github: anamba/liquid.cr

Usage

require "liquid"

txt = "
    {% if kenny.sick %}
      Kenny is sick.
    {% elsif kenny.dead %}
      You killed Kenny!  You ***!!!
    {% else %}
      Kenny looks okay --- so far
    {% endif %}
    "
ctx = Liquid::Context.new
ctx.set "kenny", { "sick" => false, "dead" => true}

tpl = Liquid::Template.parse txt  # tpl can be cached and reused

result = tpl.render ctx

# result = "
#      You killed Kenny!  You ***!!!
#
#    "

Tags can be escaped:

\{% assign myvar = 15 %}

# or

{% raw %}
{% assign myvar = 15 %}
{% endraw %}

will both render {% assign myvar = 15 %}.

Blocks

Cache block (only supports caching using Redis): https://github.com/TechMagister/liquid-cache.cr

Filters

• abs
• append
• camelcase | camelize
• capitalize
• ceil
• compact
• date
• default
• divided_by
• downcase
• escape
• escape_once
• first
• floor
• join
• last
• lstrip
• map
• minus
• modulo
• newline_to_br
• pluralize
• plus
• prepend
• remove
• remove_first
• replace
• replace_first
• reverse
• round
• rstrip
• size
• slice
• sort
• sort_natural
• split
• strip
• strip_html
• strip_newlines
• times
• truncate
• truncatewords
• underscore
• uniq
• upcase | uppercase

Helper Methods

• size (for Array and String)
• present / blank (added)
• first / last

Development

TODO:

• Basic For loops
• if/elsif/else/endif
• unless/endunless
• Raw and comment blocks ({% raw %} and {% comment %})
• Add variable assignment ({% assign var = "Hello World" %})
• Add support for multiple operator (no operator precedence support (for now))
• Add support for Array into for loop
• Add support for Hash into for loop ({% for val in myhash %}, access as val[0] and val[1])
• Add support for Hash into for loop ({% for key, val in myhash %}) (new)
• Add support for Float
• Add iteration over Arrays
• Improve data interface
• Add Filter support
• Add capture block
• Add increment block
• Add decrement block
• Add support for Array in expressions
• Add support for Hash in expressions
• Add "secret" empty Array ([]) for use in comparisons (equivalent to #blank helper method)
• Add contains operator
• Add cycle keyword
• Add starts_with keyword (new)
• Add ends_with keyword (new)
• Add continue keyword
• Add break keyword
• Add case/when
• Add syntax checking
• Improve expression parsing
• Add optional strict mode on Context (see below)
• Add Everything that's missing [https://shopify.github.io/liquid/]

Context Strict Mode

NOTE: Will eventually use this to implement a strict_variables rendering flag (planning to implement strict_filters as well).

Enable at initialization:

ctx = Liquid::Context.new(strict: true)

Or on an existing Context:

ctx.strict = true

Raises KeyError on missing keys and IndexError on array out of bounds errors instead of silently emitting nil.

Append ? to emit nil in strict mode (very simplistic, just checks for ? at the end of the identifier)

ctx = Liquid::Context.new(strict: true)
ctx["obj"] = { something: "something" }

{{ missing }}          -> KeyError
{{ missing? }}         -> nil
{{ obj.missing }}      -> KeyError
{{ obj.missing? }}     -> nil
{{ missing.missing? }} -> nil

Note on order of operations in complex expressions

Currently, comparison operators are evaluated before and/or. Other than that, evaluations are evaluated from left to right. Parentheses are not supported.

Eventually, this will be fixed to evaluate expressions in a way that mirrors Crystal itself, but for now, it would be best to simply avoid writing complex expressions.

Contributing

1. Fork it ( https://github.com/anamba/liquid.cr/fork )
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request

Contributors

• TechMagister Arnaud Fernandés - creator, maintainer of original version
• docelic Davor Ocelic
• anamba Aaron Namba