The module name is the template filename, lowercased, with _dtl appended. Directories are ignored, so templates/mail/hello.dtl is also hello_dtl. Two templates with the same filename would therefore conflict by default.

Set DTL_FULL_PATH to include the path from the template directory. Slashes become underscores, so templates/mail/hello.dtl becomes mail_hello_dtl:

DTL_FULL_PATH = 1

DTL_PREFIX is prepended to that name. It is empty by default. DTL_SUFFIX is appended and defaults to _dtl. An empty suffix keeps the template name as the module name:

DTL_PREFIX = number_
DTL_SUFFIX =

With those values, templates/one.dtl becomes number_one.

DTL_PATH selects the directory. It defaults to templates/:

DTL_PATH = priv/templates

DTL_OPTS holds Erlang terms passed to erlydtl:compile/3. They are inserted before the options added by the plugin. The plugin always writes beams to ebin/ and returns errors to the build.

DTL_OPTS = {auto_escape, false}

Several terms are comma-separated:

DTL_OPTS = auto_escape, {libraries, [{myapp, myapp_lib}]}

{libraries, [...]} is how a project registers its own ErlyDTL tags and filters. The ErlyDTL documentation describes the template language and the compiler options.

ErlyDTL inlines {% include %} and {% extends %} when it compiles a template. A quoted path is relative to the template being compiled. {doc_root, Dir} in DTL_OPTS selects another directory.

Changing a template rebuilds it. Changing a template that others include or extend also rebuilds those templates, including templates reached through a chain of includes. An unchanged template is left as-is. Changing the Makefile recompiles the templates.