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

• Liquid Template Parser
  • Installation
  • Usage
    • Command-Line tool
  • Security
  • Documentation
    • Status
    • Drops
    • Value Types
    • Template Store
    • References
  • Contributing
    • Contributors
    • Attribution
  • Other Implementations
    • Go
    • Other Languages
  • License

go get github.com/osteele/liquid # latest version

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

engine := liquid.NewEngine()
template := `<h1>{{ page.title }}</h1>`
bindings := map[string]any{
    "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>

See the API documentation for additional examples.

This library was originally developed for Gojekyll, a Go port of Jekyll. As such, it includes optional Jekyll-specific extensions that are not part of the Shopify Liquid specification.

To enable Jekyll compatibility mode:

engine := liquid.NewEngine()
engine.EnableJekyllExtensions()

Jekyll extensions include:

• Dot notation in assign tags: {% assign page.canonical_url = "/about/" %}
  • In standard Liquid, this would be a syntax error
  • With Jekyll extensions enabled, this creates or updates nested object properties
  • Intermediate objects are created automatically if they don't exist

Example:

engine := liquid.NewEngine()
engine.EnableJekyllExtensions()  // Enable Jekyll-specific features

template := `{% assign page.meta.author = "John Doe" %}{{ page.meta.author }}`
bindings := map[string]any{
    "page": map[string]any{
        "title": "Home",
    },
}
out, _ := engine.ParseAndRenderString(template, bindings)
// Output: John Doe

Note: Jekyll extensions are disabled by default to maintain compatibility with standard Shopify Liquid.

go install github.com/osteele/liquid/cmd/liquid@latest 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!

Important: If you plan to process untrusted templates (templates authored by users you don't fully trust), please review the Security Policy documentation.

Key security considerations:

• Sandboxed Execution: Templates cannot execute arbitrary code or access filesystem/network resources (by default)
• DoS Vulnerabilities: The engine is vulnerable to denial-of-service attacks via infinite loops and memory exhaustion when processing untrusted templates
• Resource Limiting via FRender: Use the FRender method with custom writers to implement timeouts and output size limits for untrusted templates
• Third-Party Extensions: Custom filters and tags execute arbitrary Go code and should be carefully audited

For detailed information about security guarantees, limitations, and production deployment recommendations, see SECURITY.md. For implementing resource limits, see the FRender documentation.

This section provides a comprehensive guide to using and extending the Liquid template engine. Documentation is organized by topic:

• Installation - Install the library and command-line tool
• Usage - Quick start guide with examples
• Command-Line Tool - Testing templates from the command line
• API Documentation - Complete API reference on pkg.go.dev

• Value Types - How Go values map to Liquid types
• Drops - Custom types in templates
• Status - Feature compatibility with Shopify Liquid

• Template Store - Custom template storage (filesystem, database, etc.)
  • See also: Template Store Example
• Advanced Rendering - FRender for streaming, timeouts, and size limits
  • See also: FRender Documentation

• Security - Resource limits and security considerations
  • See also: SECURITY.md
• FRender Documentation - Implementing resource limits in production

• Loop Semantics - Comparison with Ruby Liquid implementation
• References - Shopify Liquid documentation and resources

• CONTRIBUTING.md - How to contribute to the project
• Contributors - List of project contributors

These features of Shopify Liquid aren't implemented:

• Filter keyword parameters, for example {{ image | img_url: '580x', scale: 2 }}. [Issue #42]
• Warn and lax error modes.
• Non-strict filters. An undefined filter is currently an error.

Drops have a different design from the Shopify (Ruby) implementation. A Ruby drop sets liquid_attributes to a list of attributes that are exposed to Liquid. A Go drop implements ToLiquid() any, that returns a proxy object. Conventionally, the proxy is a map or struct that defines the exposed properties. See http://godoc.org/github.com/osteele/liquid#Drop for additional information.

Render and friends take a Bindings parameter. This is a map of string to any, that associates template variable names with Go values.

Any Go value can be used as a variable value. These values have special meaning:

• false and nil
  • These, and no other values, are recognized as false by and, or, {% if %}, {% elsif %}, and {% case %}.
• Integers
  • (Only) integers can be used as array indices: array[1]; array[n], where array has an array value and n has an integer value.
  • (Only) integers can be used as the endpoints of a range: {% for item in (1..5) %}, {% for item in (start..end) %} where start and end have integer values.
• Integers and floats
  • Integers and floats are converted to their join type for comparison: 1 == 1.0 evaluates to true. Similarly, int8(1), int16(1), uint8(1) etc. are all ==.
  • [There is currently no special treatment of complex numbers.]
• Integers, floats, and strings
  • Integers, floats, and strings can be used in comparisons <, >, <=, >=. Integers and floats can be usefully compared with each other. Strings can be usefully compared with each other, but not with other values. Any other comparison, e.g. 1 < "one", 1 > "one", is always false.
• Arrays (and slices)
  • An array can be indexed by integer value: array[1]; array[n] where n has an integer value.
  • Arrays have first, last, and size properties: array.first == array[0], array[array.size-1] == array.last (where array.size > 0)
• Maps
  • A map can be indexed by a string: hash["key"]; hash[s] where s has a string value
  • A map can be accessed using property syntax hash.key
  • Maps have a special size property, that returns the size of the map.
• Drops
  • A value value of a type that implements the Drop interface acts as the value value.ToLiquid(). There is no guarantee about how many times ToLiquid will be called. [This is in contrast to Shopify Liquid, which both uses a different interface for drops, and makes stronger guarantees.]
• Structs
  • A public field of a struct can be accessed by its name: value.FieldName, value["fieldName"].
    • A field tagged e.g. liquid:”name” is accessed as value.name instead.
    • If the value of the field is a function that takes no arguments and returns either one or two arguments, accessing it invokes the function, and the value of the property is its first return value.
    • If the second return value is non-nil, accessing the field panics instead.
  • A function defined on a struct can be accessed by function name e.g. value.Func, value["Func"].
    • The same rules apply as to accessing a func-valued public field.
  • Note that despite being array- and map-like, structs do not have a special value.size property.
• []byte
  • A value of type []byte is rendered as the corresponding string, and presented as a string to filters that expect one. A []byte is not (currently) equivalent to a string for all uses; for example, a < b, a contains b, hash[b] will not behave as expected where a or b is a []byte.
• MapSlice
  • An instance of yaml.MapSlice acts as a map. It implements m.key, m[key], and m.size.

The template store allows for usage of varying template storage implementations (embedded file system, database, service, etc). In order to use:

1. Create a struct that implements TemplateStore

   type TemplateStore interface {
         ReadTemplate(templatename string) ([]byte, error)
   }

2. Register with the engine

   engine.RegisterTemplateStore(myTemplateStore)

FileTemplateStore is the default mechanism for backwards compatibility.

Refer to example for an example implementation.

For advanced use cases like streaming to files, implementing timeouts, or limiting output size, use the FRender method to render directly to any io.Writer:

var buf bytes.Buffer
err := template.FRender(&buf, bindings)

This is particularly useful for:

• Rendering large templates without buffering in memory
• Implementing cancellation via context
• Limiting output size from untrusted templates
• Custom output transformation

See the FRender documentation for detailed examples and security best practices.

• Shopify.github.io/liquid
• Liquid for Designers
• Liquid for Programmers
• Help.shopify.com

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

Thanks goes to these wonderful people (emoji key):

Oliver Steele 💻 📖 🤔 🚇 👀 ⚠️	James Littlejohn 💻 📖 ⚠️	nsf 💻 ⚠️	Tobias Salzmann 💻	Ben Doerr 💻	Daniil Gentili 💻	Carolyn Van Slyck 💻
Kimmo Lehto 💻	Victor "Vito" Gama 💻	Utpal Sarkar 💻 ⚠️

This project follows the all-contributors specification. Contributions of any kind welcome!

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.

• 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

See Shopify's ports of Liquid to other environments.

MIT License