A cache of parsed templates across renders, like the template cache of a Jinja2 Environment.

Without a cache, Otera loads and parses each template once in a render. With the :cache option of Otera.load/2 and Otera.render/3, it keeps the parsed templates of a loader for the next renders. The cache is an ETS table that a process owns, so start it in the supervision tree of your application:

children = [
  {Otera.Cache, name: MyApp.Templates}
]

Then give its name with the loader:

opts = [loader: Otera.Loader.file_system("priv/templates"), cache: MyApp.Templates]
{:ok, template} = Otera.load("page.html", opts)
Otera.render(template, %{title: "Home"}, opts)

The cache keeps a template for each loader, name and parse options (:trim_blocks, :lstrip_blocks, :keep_trailing_newline and the names of the custom filters and tests). Like the auto reload of Jinja2, it checks a template before it uses it:

• A template of Otera.Loader.file_system/1 loads again when the modification time or the size of its file changes. The time has a resolution of one second.
• A template of a map loads again when the map has another source for its name, like the DictLoader of Jinja2.
• A template of a function loads again when the function gave an uptodate function with the source and that function returns false, like the FunctionLoader of Jinja2. Without it, the template stays until clear/1.

These checks have a cost: a file system loader reads the status of each file at each render. Like auto_reload=False in Jinja2, start the cache with auto_reload: false to use each template without a check until clear/1:

{Otera.Cache, name: MyApp.Templates, auto_reload: false}