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Django templates for Erlang
Erlang Other
Tag: 0.8.1

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ErlyDTL Build Status

ErlyDTL compiles Django Template Language to Erlang bytecode.

Project homepage:

ErlyDTL implements the Django Template Language as documented for version 1.6, here:

Despite our best efforts to be completely compatible with the Django Template Languge, there are still a few differences.


To compile ErlyDTL, run


in this directory.

Template compilation


erlydtl:compile("/path/to/template.dtl", my_module_name)

erlydtl:compile("/path/to/template.dtl", my_module_name, Options)

erlydtl:compile(<<"<html>{{ foo }}</html>">>, my_module_name)

erlydtl:compile(<<"<html>{{ foo }}</html>">>, my_module_name, Options)


ok %% existing compiled template is up to date.

{ok, Module}
{ok, Module, Warnings}
{ok, Module, Binary}
{ok, Module, Binary, Warnings}

{error, Errors, Warnings}

Options is a proplist possibly containing:

  • out_dir - Directory to store generated .beam files. If not specified, no .beam files will be created.

  • doc_root - Included template paths will be relative to this directory; defaults to the compiled template's directory.

  • custom_tags_dir - Directory of DTL files (no extension) includable as tags. E.g. if $custom_tags_dir/foo contains <b>{{ bar }}</b>, then {% foo bar=100 %} will evaluate to <b>100</b>. Get it?

  • custom_tags_modules - A list of modules to be used for handling custom tags. The modules will be searched in order and take precedence over custom_tags_dir. Each custom tag should correspond to an exported function with one of the following signatures:

    some_tag(TagVars)          -> iolist()
    some_tag(TagVars, Options) -> iolist()

    The TagVars are variables provided to a custom tag in the template's body (e.g. {% foo bar=100 %} results in TagVars = [{bar, 100}]). The Options are options passed as the second argument to the render/2 call at render-time. (These may include any options, not just locale and translation_fun.)

  • custom_filters_modules - A list of modules to be used for handling custom filters. The modules will be searched in order and take precedence over the built-in filters. Each custom filter should correspond to an exported filter, e.g.

    some_filter(Value) -> iolist()

    If the filter takes an argument (e.g. "foo:2"), the argument will be also be passed in:

    some_filter(Value, Arg) -> iolist()
  • vars - Variables (and their values) to evaluate at compile-time rather than render-time. (Currently not strictly true, see #61)

  • reader - {module, function} tuple that takes a path to a template and returns a binary with the file contents. Defaults to {file, read_file}. Useful for reading templates from a network resource.

  • force_recompile - Recompile the module even if the source's checksum has not changed. Useful for debugging.

  • locale - The locale used for template compile. Requires erlang_gettext. It will ask gettext_server for the string value on the provided locale. For example, adding {locale, "en_US"} will call {key2str, Key, "en_US"} for all string marked as trans ({% trans "StringValue" %} on templates). See README_I18N.

  • blocktrans_fun - A two-argument fun to use for translating blocktrans blocks. This will be called once for each pair of blocktrans block and locale specified in blocktrans_locales. The fun should take the form:

    Fun(Block::string(), Locale::string()) -> <<"ErlyDTL code">> | default
  • blocktrans_locales - A list of locales to be passed to blocktrans_fun. Defaults to [].

  • binary_strings - Whether to compile strings as binary terms (rather than lists). Defaults to true.

  • record_info - List of records to look for when rendering the template. Each record info is a tuple with the fields of the record:

    {my_record, record_info(fields, my_record)}
  • no_env - Do not read additional options from the OS environment variable ERLYDTL_COMPILER_OPTIONS.

  • auto_escape - Turn on auto escape by default (this is on by default in Django).

  • no_load - Do not load the compiled template.

  • binary - Include the compiled template binary code in the result tuple (between the module name and any warning/error lists). Note, this option is named the same as for the Erlang compiler, with similar use, except that this option does NOT affect whether or not a .beam file is saved.

  • return - Short form for both return_warnings and return_errors.

  • return_warnings - If this flag is set, then an extra field containing warnings is added to the tuple returned on success.

  • return_errors - If this flag is set, then an error-tuple with two extra fields containing errors and warnings is returned when there are errors.

  • report - Short form for both report_warnings and report_errors.

  • report_warnings - Print warnings as they occur.

  • report_errors - Print errors as they occur.

  • warnings_as_errors - Treat warnings as errors.

  • verbose - Enable verbose printing of compilation results.

  • compiler_options - Proplist with extra options passed directly to compiler:forms/2. This can prove useful when using extensions to add extra defines etc when compiling the generated code.

Helper compilation

Helpers provide additional templating functionality and can be used in conjunction with the custom_tags_module option above. They can be created from a directory of templates thusly:

erlydtl:compile_dir("/path/to/dir", my_helper_module_name)

erlydtl:compile_dir("/path/to/dir", my_helper_module_name, Options)

The resulting module will export a function for each template appearing in the specified directory. Options is the same as for compile/3.

Compiling a helper module can be more efficient than using custom_tags_dir because the helper functions will be compiled only once (rather than once per template).

Usage (of a compiled template)

my_compiled_template:render(Variables) -> {ok, IOList} | {error, Err}

Variables is a proplist, dict, gb_tree, or a parameterized module (whose method names correspond to variable names). The variable values can be atoms, strings, binaries, or (nested) variables.

IOList is the rendered template.

my_compiled_template:render(Variables, Options) ->
        {ok, IOList} | {error, Err}

Same as render/1, but with the following options:

  • translation_fun - A fun/1 that will be used to translate strings appearing inside {% trans %} tags. The simplest TranslationFun would be fun(Val) -> Val end

  • locale - A string specifying the current locale, for use with the blocktrans_fun compile-time option.

    my_compiled_template:translatable_strings() -> [String]

    List of strings appearing in {% trans %} tags that can be overridden with a dictionary passed to render/2.

    my_compiled_template:translated_blocks() -> [String]

    List of strings appearing in {% blocktrans %}...{% endblocktrans %} blocks; the translations (which can contain ErlyDTL code) are hard-coded into the module and appear at render-time. To get a list of translatable blocks before compile-time, use the provided blocktrans_extractor module.

    my_compiled_template:source() -> {FileName, CheckSum}

    Name and checksum of the original template file.

    my_compiled_template:dependencies() -> [{FileName, CheckSum}]

    List of names/checksums of templates included by the original template file. Useful for frameworks that recompile a template only when the template's dependencies change.

    my_compiled_template:variables() -> [Variable::atom()]

    Sorted list of unique variables used in the template's body. The list can be used for determining which variable bindings need to be passed to the render/3 function.

Differences from standard Django Template Language

  • auto_escape is not enabled by default in ErlyDTL. Pass the auto_escape option when compiling your template if you need this.

  • csrf_token The Cross Site Request Forgery tag is not implemented.

  • url The url tag is not implemented. This should be addressed in a future release.
  • regroup requires a closing endregroup tag. See Issue #101.


From a Unix shell, run:

make test

Note that the tests will create some output in tests/output.

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