Revel by default uses Go’s built in html/template package. For information regarding this template engine see here

To add a template engine you must include the module. For example

module.1.pongo2=github.com/revel/modules/template-engine/pongo2
module.2.ace=github.com/revel/modules/template-engine/ace
module.3.static=github.com/revel/modules/static
module.4.jobs=github.com/revel/modules/jobs

This specifies that the pongo2 and ace engines are added to the main template parser, the order of the way the modules are loaded is important as well, since that controls what view overrides another. The first view found is always the view used, all others will be suppressed. The two part key allows the modules to be sorted, after sorting the sort key is removed and in the routes table the route is referenced normally.

The configuration file also needs an list of engines to be used on the views this is where template.engines key in the configuration file comes into play like

template.engines=pongo2,ace,go

The three template engines pongo2,ace,go will be used when rendering templates.

How Revel Picks the Right Template Engine

The template-engine has a method called Handles, which accepts the basic template information (path, and content). The engine then can return true or false if it can parse the file or not. How it makes this choice is up to the parser. Revel has a builtin function called revel.EngineHandles, which can be used to look for a shebang at the top of the template to see which template engine it belongs to, it also looks for a secondary extension like foo.ace.html which would be identified as an ace template. Finally it could try to parse the code and if that passes it can register itself for that.

File Path Case Sensitivity

In the past we have maintained an all lower case template path, this works in most cases but lead to some confusion. For example if you include a file within your template you must type out the file and file path in lower case. Now you can specify if the case sensitivity is on or off. The case sensitivity can be turned on by setting an app configuration option per template engine like go.tempate.path=case will turn on case sensitivity on the go template engine (by default it is off).

Directory Scanning

Directories are scanned for templates in the following order:

  1. The application app/views/ directory and subdirectories.
  2. revel core templates/ directory.
  3. Otherwise a 500 error as template not found (but in dev mode shows debug info)

For example, given a controller/action Hello.World(), Revel will:

  • look for a template file named views/Hello/World.html.
  • and if not found, show views/errors/500.html
  • and if that’s not found, use Revel’s built-in templates/errors/500.html

Template file names are case insensitive so the following will be treated as the same:

  • views/hello/world.html
  • views/HeLlO/wOrLd.HtMl

However, on **nix based file systems (and for example with index.html and IndeX.html), duplicate cased file names are to be avoided as it is unpredictable which one will be considered.

Revel provides templates for error pages (see code) and these display the developer friendly compilation errors in dev mode. An application may override them by creating a template of the equivalent template name, e.g. app/views/errors/404.html.

Render Context

Revel executes the template using the ViewArgs data map[string]interface{}. Aside from application-provided data, Revel provides the following entries:

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