Mustache Template Engine for Go

Why a Fork?

I forked hoisie/mustache because it does not appear to be maintained, and I wanted to add the following functionality:

Update the API to follow the idiomatic Go convention of returning errors (this is a breaking change)
Add option to treat missing variables as errors

Overview

This library is an implementation of the Mustache template language in Go.

Mustache Spec Compliance

https://github.com/mustache/spec contains the formal standard for Mustache, and it is added as a submodule (using v1.1.3) for testing compliance. Currently ~40% of tests are failing, and the optional lambda support is not implemented. You can see which tests are disabled (b/c they are failing) by looking at spec_test.go. Getting all tests passing is my top priority (time permitting), and any PRs to that end are welcome.

Documentation

For more information about mustache, check out the mustache project page or the mustache manual.

Also check out some example mustache files

Installation

To install mustache.go, simply run go get github.com/cbroglie/mustache. To use it in a program, use import "github.com/cbroglie/mustache"

Usage

There are four main methods in this package:

Render(data string, context ...interface{}) (string, error)

RenderFile(filename string, context ...interface{}) (string, error)

ParseString(data string) (*Template, error)

ParseFile(filename string) (*Template, error)

There are also two additional methods for using layouts (explained below); as well as several more that can provide a custom Partial retrieval.

The Render method takes a string and a data source, which is generally a map or struct, and returns the output string. If the template file contains an error, the return value is a description of the error. There's a similar method, RenderFile, which takes a filename as an argument and uses that for the template contents.

data, err := mustache.Render("hello {{c}}", map[string]string{"c": "world"})

If you're planning to render the same template multiple times, you do it efficiently by compiling the template first:

tmpl, _ := mustache.ParseString("hello {{c}}")
var buf bytes.Buffer
for i := 0; i < 10; i++ {
    tmpl.FRender(&buf, map[string]string{"c": "world"})
}

For more example usage, please see mustache_test.go

Escaping

mustache.go follows the official mustache HTML escaping rules. That is, if you enclose a variable with two curly brackets, {{var}}, the contents are HTML-escaped. For instance, strings like 5 > 2 are converted to 5 > 2. To use raw characters, use three curly brackets {{{var}}}.

Layouts

It is a common pattern to include a template file as a "wrapper" for other templates. The wrapper may include a header and a footer, for instance. Mustache.go supports this pattern with the following two methods:

RenderInLayout(data string, layout string, context ...interface{}) (string, error)

RenderFileInLayout(filename string, layoutFile string, context ...interface{}) (string, error)

The layout file must have a variable called {{content}}. For example, given the following files:

layout.html.mustache:

<html>
<head><title>Hi</title></head>
<body>
{{{content}}}
</body>
</html>

template.html.mustache:

<h1>Hello World!</h1>

A call to RenderFileInLayout("template.html.mustache", "layout.html.mustache", nil) will produce:

<html>
<head><title>Hi</title></head>
<body>
<h1>Hello World!</h1>
</body>
</html>

Custom PartialProvider

Mustache.go has been extended to support a user-defined repository for mustache partials, instead of the default of requiring file-based templates.

Several new top-level functions have been introduced to take advantage of this:

func RenderPartials(data string, partials PartialProvider, context ...interface{}) (string, error)

func RenderInLayoutPartials(data string, layoutData string, partials PartialProvider, context ...interface{}) (string, error)

func ParseStringPartials(data string, partials PartialProvider) (*Template, error)

func ParseFilePartials(filename string, partials PartialProvider) (*Template, error)

A PartialProvider is any object that responds to Get(string) (*Template,error), and two examples are provided- a FileProvider that recreates the old behavior (and is indeed used internally for backwards compatibility); and a StaticProvider alias for a map[string]string. Using either of these is simple:

fp := &FileProvider{
  Paths: []string{ "", "/opt/mustache", "templates/" },
  Extensions: []string{ "", ".stache", ".mustache" },
}

tmpl, err := ParseStringPartials("This partial is loaded from a file: {{>foo}}", fp)

sp := StaticProvider(map[string]string{
  "foo": "{{>bar}}",
  "bar": "some data",
})

tmpl, err := ParseStringPartials("This partial is loaded from a map: {{>foo}}", sp)

A note about method receivers

Mustache.go supports calling methods on objects, but you have to be aware of Go's limitations. For example, lets's say you have the following type:

type Person struct {
    FirstName string
    LastName string
}

func (p *Person) Name1() string {
    return p.FirstName + " " + p.LastName
}

func (p Person) Name2() string {
    return p.FirstName + " " + p.LastName
}

While they appear to be identical methods, Name1 has a pointer receiver, and Name2 has a value receiver. Objects of type Person(non-pointer) can only access Name2, while objects of type *Person(person) can access both. This is by design in the Go language.

So if you write the following:

mustache.Render("{{Name1}}", Person{"John", "Smith"})

It'll be blank. You either have to use &Person{"John", "Smith"}, or call Name2

Supported features

Variables
Comments
Change delimiter
Sections (boolean, enumerable, and inverted)
Partials

tetrode/mustache