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ErlyDTL Build Status

ErlyDTL compiles Django Template Language to Erlang bytecode.

Project homepage: https://github.com/erlydtl/erlydtl/wiki

ErlyDTL implements the Django Template Language as documented for version 1.6, here: http://docs.djangoproject.com/en/1.6/ref/templates/builtins/

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

The erlydtl branches & tags

As things are progressing somewhat more rapidly, I'll describe our branch and tagging strategy to help you stay on the branch or tag(s) that suits you best.

master branch

This is were all the action is, and at times may be slightly broken. Suitable for early adopters who aren't afraid of a little debugging and hopefully also reporting issues.

release tags

Whenever master is deemed stable with a nice set of additions/changes, it may be up for a new release.

As we're still going for the big 1.0 release, breaking changes may be introduced also on minor release bumps; but after that, we'll stick with semver (as a matter of fact, this is all covered by the Semantic Versioning Spec 2.0.0, see 4§).

stable branch

The stable branch Will follow the latest release after it has proven itself stable. This is a bit fuzzy, what will be considered stable, but if you want to follow the releases without having to keep track of when to jump to a new tag, the stable branch is for you.

Compilation

To compile ErlyDTL, run

make

in this directory.

Template compilation

Usage:

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

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

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

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

Result:

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

error
{error, Errors, Warnings}

Options is a proplist possibly containing:

  • auto_escape - Control automatic HTML escaping of template values. Enabled by default.

  • 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.

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

  • blocktrans_fun - A two-argument fun to use for translating blocktrans blocks, trans tags and _(..) expressions. This will be called once for each pair of translated element and locale specified in blocktrans_locales. The fun should take the form:

    Fun(Block::string(), Locale::string()) -> <<"ErlyDTL code">>::binary() | default

  • blocktrans_locales - A list of locales to be passed to blocktrans_fun. Defaults to [].

  • 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.

  • custom_filters_modules deprecated - 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 any arguments (e.g. "foo:2"), those will be added to the call:

    some_filter(Value, Arg) -> iolist()

  • 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>.

  • custom_tags_modules deprecated - 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.)

  • debug_compiler - Enable compiler debug diagnostics. Currently it debug prints the options passed to compile:forms (i.e. if verbosity is >= 2; that is, with two or more verbose options) and enables the saving of the compiled template in source form to a .erl file.

  • debug_info - This option is passed to compile:forms to include debug information in the compiled module.

  • debug_root - Only applies when debug_compiler is true. The root directory for debug source dumps. If set to false, no source dump will be saved. Defaults to undefined, leaving the source dump next to the source template file.

  • default_libraries - A list of libraries that should be loaded by default when compiling a template. Libraries can be specified either by name (when there is a name to module mapping also provided in the libraries option) or by module.

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

  • extension_module experimental - This is work in progress to make erlydtl extensible.

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

  • libraries - A list of {Name, Module} libraries implementing custom tags and filters. Module should implement the erlydtl_library behaviour.

  • locale deprecated - The same as {blocktrans_locales, [Val]}.

  • no_env - Do not read additional options from the OS environment variable ERLYDTL_COMPILER_OPTIONS.

  • no_load - Do not load the compiled template.

  • out_dir - Directory to store generated .beam files. If not specified, no .beam files will be created and a warning is emitted. To silence the warning, use {out_dir, false}.

  • 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.

  • 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)}

  • 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.

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

  • verbose - Enable verbose printing of compilation progress. Add several for even more verbose (e.g. debug) output.

  • warnings_as_errors - Treat warnings as errors.

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).

Notice: The exported template functions return an iolist() on success only, failures are non-local (e.g. as a throw). To get the result in wrapped tuple {ok, iolist()} | {error, Reason} call one of the render functions: render(Tag) | render(Tag, Vars) | render(Tag, Vars, Opts).

Usage (of a compiled template)

render/1

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.

render/2

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 %} and {% blocktrans %} tags. The simplest TranslationFun would be fun(Val) -> Val end. Placeholders for blocktrans variable interpolation should be wrapped to {{ and }}.

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

translatable_strings/0

my_compiled_template:translatable_strings() -> [String]

List of strings appearing in {% trans %} and _(..) tags.

translated_blocks/0

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.

source/0

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

Name and checksum of the original template file.

dependencies/0

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.

variables/0

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

Tests

From a Unix shell, run:

make tests

Note that the tests will create some output in tests/output in case of regressions.

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