django-render-block 0.5

Render a particular block from a template to a string.

Django Render Block
###################

.. image:: https://travis-ci.org/clokep/django-render-block.svg?branch=master
:target: https://travis-ci.org/clokep/django-render-block

Render the content of a specific block tag from a Django template. Works for
arbitrary template inheritance, even if a block is defined in the child template
but not in the parent. Generally it works like ``render_to_string`` from Django,
but allows you to specify a block to render.

Features
========

* Render a specific block from a template
* Fully supports the Django templating engine
* Partially supports the `Jinja2 <http://jinja.pocoo.org/>`_ engine: it does
not currently process the ``extends`` tag.

Requirements
============

Django Render Block supports Django 1.8 and 1.9.

Examples
========

In ``test1.html``:

.. code-block:: jinja

{% block block1 %}block1 from test1{% endblock %}
{% block block2 %}block2 from test1{% endblock %}

In ``test2.html``:

.. code-block:: jinja

{% extends 'test1.html' %}
{% block block1 %}block1 from test2{% endblock %}

And from the Python shell:

.. code-block:: python

>>> from render_block import render_block_to_string
>>> print render_block_to_string('test2.html', 'block1')
u'block1 from test2'
>>> print render_block_to_string('test2.html', 'block2')
u'block2 from test1'

It can also accept a context as a ``dict`` (just like ``render_to_string``), in
``test3.html``:

.. code-block:: jinja

{% block block3 %}Render this {{ variable }}!{% endblock %}

And from Python:

.. code-block:: python

>>> print render_block_to_string('test3.html', 'block3', {'variable': 'test'})
u'Render this test!'

API Reference
=============

The API is simple and attempts to mirror the built-in ``render_to_string`` API.

``render_block_to_string(template_name, block_name, context=None)``

``template_name``
The name of the template to load and render. If it’s a list of template
names, Django uses ``select_template()`` instead of ``get_template()``
to find the template.

``block_name``
The name of the block to render from the above template.

``context``
A ``dict`` to be used as the template’s context for rendering.

``context`` is now optional. An empty context will be used if it isn’t
provided.

Exceptions
----------

Like ``render_to_string`` this will raise the following exceptions:

``TemplateDoesNotExists``
Raised if the template(s) specified by ``template_name`` cannot be
loaded.

``TemplateSyntaxError``
Raised if the loaded template contains invalid syntax.

There are also two additional errors that can be raised:

``BlockNotFound``
Raised if the block given by ``block_name`` does not exist in the
template.

``UnsupportedEngine``
Raised if a template backend besides the Django backend is used.

Contributing
============

If you find a bug or have an idea for an improvement to Django Render Block,
please
`file an issue <https://github.com/clokep/django-render-block/issues/new>`_ or
provide a pull request! Check the
`list of issues <https://github.com/clokep/django-render-block/issues/>`_ for
ideas of what to work on.

Attribution
===========

This is based on a few sources:

* Originally `Django Snippet 769 <https://djangosnippets.org/snippets/769/>`_
* Updated version `Django Snippet 942 <https://djangosnippets.org/snippets/942/>`_
* A version of the snippets was ported as `Django-Block-Render <https://github.com/uniphil/Django-Block-Render/>`_
* Additionally inspired by part of `django-templated-email <https://github.com/BradWhittington/django-templated-email/blob/master/templated_email/utils.py>`_
* Also based on a `StackOverflow answer 2687173 <http://stackoverflow.com/questions/2687173/django-how-can-i-get-a-block-from-a-template>`_
.. :changelog:

Changelog
#########

0.5 (September 1, 2016)
=======================

* Fixes a major issue with inheriting templates and rendering a block found in
the parent template, but overwriting part of it in the child template.
(`#8 <https://github.com/clokep/django-render-block/pull/8>`_)

0.4 (August 4, 2016)
====================

* Initial support for using the `Jinja2 <http://jinja.pocoo.org/>`_ templating
engine. See README for caveats. (`#3 <https://github.com/clokep/django-render-block/pull/3>`_)
* Support Django 1.10. (`#5 <https://github.com/clokep/django-render-block/pull/5>`_)
* Support Python 3. (`#6 <https://github.com/clokep/django-render-block/pull/6>`_)

0.3.1 (June 1, 2016)
====================

* Refactoring to make more generic (for potentially supporting multiple
templating engines).

0.3 (May 27, 2016)
==================

* Largely rewritten.
* Updated to support modern Django (1.8, 1.9):

* Guards against different template backends.
* Uses internal APIs for each node.
* Removed ``context_instance`` parameter.
* Support for calling ``{{ block.super }}``.

0.2.2 (January 10, 2011)
========================

* Updated per
`comment 3466 on Django Snippet 942 <https://djangosnippets.org/snippets/942/#c3466>`_
to fix an issue with nested extends. The specific bug was not reproducible,
but the additional code shouldn't hurt.

0.2.1 (August 27, 2010)
=======================

* Updated per
`comment 3237 on Django Snippet 942 <https://djangosnippets.org/snippets/942/#c3237>`_
to remove a pointless render. The specific bug was not reproducible, but the
code is extraneous.

0.2 (August 4, 2008)
====================

* Updated version from
`Django Snippet 942 <https://djangosnippets.org/snippets/942/>`_ by zbyte64.
* Improves include:

1. Simpler/better handling of "extends" block tag
2. Searches If/Else blocks
3. Less code
4. Allow list of templates to be passed which is closer to the behavior of
render_to_response


0.1 (May 22, 2008)
==================

* Initial version from
`Django Snippet 769 <https://djangosnippets.org/snippets/769/>`_ by sciyoshi.
* Supports Django 0.96.