liquid/README.md

Liquid Template Parser

liquid is a Go implementation of Shopify Liquid templates. It was developed for use in the Gojekyll static site generator.

“Any sufficiently complicated C or Fortran program contains an ad-hoc, informally-specified, bug-ridden, slow implementation of half of Common Lisp.” – Philip Greenspun

• Liquid Template Parser
  • Differences from Liquid
  • Stability
  • Install
  • Usage
    • Command-Line tool
  • Contributing
  • References
  • Attribution
  • Other Implementations
    • Go
    • Other Languages
  • License

Differences from Liquid

The feature parity board lists differences from Liquid.

In brief, these aren't implemented:

• Warn and lax error modes.
• Non-strict filters. An undefined filter is currently an error.
• Strict variables. An undefined variable is not an error.

Stability

This library is at an early stage of development. It has been mostly used by its author.

Only the liquid package itself, and the sub-package types that are used in that top-level package, are guaranteed stable. For example, render.Context is documented as the parameter type for tag definitions; it therefore won't change incompatibly with minor versions.

Install

go get gopkg.in/osteele/liquid.v1 # latest snapshot

go get -u github.com/osteele/goliquid # development version

Usage

engine := liquid.NewEngine()
template := `<h1>{{ page.title }}</h1>`
bindings := map[string]interface{}{
    "page": map[string]string{
        "title": "Introduction",
    },
}
out, err := engine.ParseAndRenderString(template, bindings)
if err != nil { log.Fatalln(err) }
fmt.Println(out)
// Output: <h1>Introduction</h1>

Command-Line tool

go install gopkg.in/osteele/liquid.v0/cmd/liquid installs a command-line liquid executable. This is intended to make it easier to create test cases for bug reports.

$ liquid --help
usage: liquid [FILE]
$ echo '{{ "Hello World" | downcase | split: " " | first | append: "!"}}' | liquid
hello!

Contributing

Bug reports, test cases, and code contributions are more than welcome. Please refer to the contribution guidelines.

References

• Shopify.github.io/liquid
• Liquid for Designers
• Liquid for Programmers
• Help.shopify.com goes into more detail, but includes features that aren't present in core Liquid as used by Jekyll.

Attribution

Package	Author	Description	License
Ragel	Adrian Thurston	scanning expressions	MIT
gopkg.in/yaml.v2	Canonical	YAML support (for printing parse trees)	Apache License 2.0

Michael Hamrah's Lexing with Ragel and Parsing with Yacc using Go was essential to understanding go yacc.

The original Liquid engine, of course, for the design and documentation of the Liquid template language. Many of the tag and filter test cases are taken directly from the Liquid documentation.

Other Implementations

Go

• karlseguin/liquid is a dormant implementation that inspired a lot of forks.
• acstech/liquid is a more active fork of Karl Seguin's implementation.
• hownowstephen/go-liquid

Other Languages

See Shopify's ports of Liquid to other environments.

License

MIT License