Grammar for Shopify Liquid!

[S0AndS0]

I've been learning the Pest, and some Rust with it too, and thought I might share a project I published today!

TLDR: Liquid is a templating language, often used for generating static web-sites.

• Crates: https://crates.io/crates/liquid-grammar-pest
• Source: https://github.com/rust-utilities/liquid-grammar-pest
• Grammar: https://github.com/rust-utilities/liquid-grammar-pest/blob/main/src/grammars/liquid.pest
• Spec: https://shopify.github.io/liquid/

---

There are a number of flavors of Liquid but, for reasons, I chose to target the core Shopify variant first; specification can be found on their GitHub Pages site.

Note; attempts have been made to ensure the base grammar allows for consuming crates to implement additional features from other Liquid flavors. But I've no doubt something(s) may have been missed X-D

Example -- Liquid

{% assign name = include.name | default: 'WaT' %}

{%- for item in site.collection[name] %}
  {%- if item.published %}
    <p>Item: {{ item }}</p>
  {%- endif %}
{%- endfor %}

Note; the prefixed hyphens ({%-) are for Whitespace control, and capturing the variants of stripping before, after, or both kinda bloated the Pest definitions.

Example -- Parser result

- document
  - liquid__tag__assign
    - liquid__tag__open__plain: "{%"
    - liquid__code__assign
      - liquid__key_word__assign: "assign"
      - liquid__code__assign__key > object__word: "name"
      - liquid__code__assign__value > liquid__type > object
        - object__word: "include"
        - object__accessor > object__property > object__word: "name"
      - liquid__filter__list > liquid__filter__default
        - liquid__key_word__filter__default: "default"
        - colon: ":"
        - liquid__filter__default__value > liquid__type > string > string__quote__single
          - quote__single: "'"
          - string__quote__single__content: "WaT"
          - quote__single: "'"
    - liquid__tag__close__plain: "%}"
  - content__block: "\n\n"
  - liquid__block__iteration__for > liquid__block__iteration__for__strip_leading
    - liquid__block_subsection__iteration__for__strip_leading__start
      - liquid__tag__open__strip: "{%-"
      - liquid__key_word__iteration__for: "for"
      - object__word: "item"
      - liquid__code__iteration__target > object
        - object__word: "site"
        - object__accessor
          - object__property > object__word: "collection"
          - object__accessor > object__key
            - bracket__square__open: "["
            - object > object__word: "name"
            - bracket__square__close: "]"
      - liquid__tag__close__plain: "%}"
      - content__block: "\n  "
      - liquid__block__control_flow__branch__within_iteration > liquid__block__control_flow__branch__within_iteration__strip_leading
        - liquid__block_subsection__control_flow__branch__within_iteration__strip_leading__start
          - liquid__tag__open__strip: "{%-"
          - liquid__key_word__control_flow__branch: "if"
          - liquid__code__control_flow__branch__comparison__expression > liquid__code__control_flow__branch__comparison__operator__word > liquid__type > object
            - object__word: "item"
            - object__accessor > object__property > object__word: "published"
          - liquid__tag__close__plain: "%}"
          - content__block: "\n    <p>Item: {{ item }}</p>\n  "
        - liquid__tag__strip_leading__end
          - liquid__tag__open__strip: "{%-"
          - liquid__code__end: "endif"
          - liquid__tag__close__plain: "%}"
      - content__block: "\n"
    - liquid__tag__strip_leading__end
      - liquid__tag__open__strip: "{%-"
      - liquid__code__end: "endfor"
      - liquid__tag__close__plain: "%}"
  - content__block: "\n"
  - EOI: ""

At this time I'd be super grateful for some bug reports, and any suggestions that'd make the src/grammars/liquid.pest easier for consuming crates to utilize.

[tomtau]

Nice! Feel free to open a PR to add it to this list here: https://github.com/pest-parser/awesome-pest