soy

Overview ¶

Package soy is an implementation of Google's Closure Templates, which are data-driven templates for generating HTML.

Compared to html/template, Closure Templates have a few advantages

• Intuitive templating language that supports simple control flow, expressions and arithmetic.
• The same templates may be used from Go, Java, and Javascript.
• Internationalization is built in

and specific to this implementation:

• High performance (> 3x faster than html/template in BenchmarkSimpleTemplate)
• Hot reload for templates
• Parse a directory tree of templates

Refer to the official language spec for details:

https://developers.google.com/closure/templates/

Template example ¶

Here is Hello World

{namespace examples.simple}

/**
 * Says hello to the world.
 */
{template .helloWorld}
  Hello world!
{/template}

Here is a more customized version that addresses us by name and can use greetings other than "Hello".

/**
 * Greets a person using "Hello" by default.
 * @param name The name of the person.
 * @param? greetingWord Optional greeting word to use instead of "Hello".
 */
{template .helloName}
  {if not $greetingWord}
    Hello {$name}!
  {else}
    {$greetingWord} {$name}!
  {/if}
{/template}

This last example renders a greeting for each person in a list of names.

It demonstrates a [foreach] loop with an [ifempty] command. It also shows how to call other templates and insert their output using the [call] command. Note that the [data="all"] attribute in the call command passes all of the caller's template data to the callee template.

/**
 * Greets a person and optionally a list of other people.
 * @param name The name of the person.
 * @param additionalNames The additional names to greet. May be an empty list.
 */
{template .helloNames}
  // Greet the person.
  {call .helloName data="all" /}<br>
  // Greet the additional people.
  {foreach $additionalName in $additionalNames}
    {call .helloName}
      {param name: $additionalName /}
    {/call}
    {if not isLast($additionalName)}
      <br>  // break after every line except the last
    {/if}
  {ifempty}
    No additional people to greet.
  {/foreach}
{/template}

This example is from https://developers.google.com/closure/templates/docs/helloworld_java.

Many more examples of Soy language features/commands may be seen here: https://github.com/robfig/soy/blob/master/testdata/features.soy

Usage example ¶

These are the high level steps:

• Create a soy.Bundle and add templates to it (the literal template strings, files, or directories).
• Compile the bundle of templates, resulting in a "Tofu" instance. It provides access to all your soy.
• Render a HTML template from Tofu by providing the template name and a data object.

Typically in a web application you have a directory containing views for all of your pages. For example:

app/views/
app/views/account/
app/views/feed/
...

This code snippet will parse a file of globals, all Soy templates within app/views, and provide back a Tofu intance that can be used to render any declared template. Additionally, if "mode == dev", it will watch the Soy files for changes and update your compiled templates in the background (or log compile errors to soy.Logger). Error checking is omitted.

On startup:

tofu, _ := soy.NewBundle().
    WatchFiles(true).                     // watch Soy files, reload on changes
    AddGlobalsFile("views/globals.txt").  // parse a file of globals
    AddTemplateDir("views").              // load *.soy in all sub-directories
    CompileToTofu()

To render a page:

var obj = map[string]interface{}{
  "user":    user,
  "account": account,
}
tofu.Render(resp, "acme.account.overview", obj)

Structs may be used as the data context too, but keep in mind that they are converted to data maps -- unlike html/template, the context is pure data, and you can not call methods on it.

var obj = HomepageContext{
  User:    user,
  Account: account,
}
tofu.Render(resp, "acme.account.overview", obj)

See soyhtml.StructOptions for knobs to control how your structs get converted to data maps.

Project Status ¶

The goal is full compatibility and feature parity with the official Closure Templates project.

The server-side templating functionality is well tested and nearly complete, except for two notable areas: contextual autoescaping and internationalization/bidi support. Contributions welcome.

The Javascript generation is early and lacks many generation options, but it successfully passes the server-side template test suite. Note that it is possible to run the official Soy compiler to generate your javascript templates at build time, even if you use this package for server-side templates.

Please see the TODO file for features that have yet to be implemented.

Please open a Github Issue for any bugs / problems / comments, or if you find a template that renders differently than with the official compiler.