/usr/lib/python2.7/dist-packages/cement/ext/ext_handlebars.py is in python-cement 2.10.0-1.
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The Handlebars Extension provides output templating based on the
`Handlebars Templating Language <https://github.com/wbond/pybars3>`_.
Requirements
------------
* pybars3 (``pip install pybars3``)
Configuration
-------------
Application Meta-data
^^^^^^^^^^^^^^^^^^^^^
This extension supports the following application meta-data via
``CementApp.Meta``:
* **handlebars_helpers** - A dictionary of helper functions to register
with the compiler. Will **override**
``HandlebarsOutputHandler.Meta.helpers``.
* **handlebars_partials** - A list of partials (template file names) to
search for, and pre-load before rendering templates. Will **override**
``HandlebarsOutputHandler.Meta.partials``.
Template Directories
^^^^^^^^^^^^^^^^^^^^
To **prepend** a directory to the ``template_dirs`` list defined by the
application/developer, an end-user can add the configuration option
``template_dir`` to their application configuration file under the main
config section:
.. code-block:: text
[myapp]
template_dir = /path/to/my/templates
Usage
-----
.. code-block:: python
class MyApp(CementApp):
class Meta:
label = 'myapp'
extensions = ['handlebars']
output_handler = 'handlebars'
template_module = 'myapp.templates'
template_dirs = [
'~/.myapp/templates',
'/usr/lib/myapp/templates',
]
# ...
Note that the above ``template_module`` and ``template_dirs`` are the
auto-defined defaults but are added here for clarity. From here, you
would then put a Handlebars template file in
``myapp/templates/my_template.handlebars`` or
``/usr/lib/myapp/templates/my_template.handlebars`` and then render a data
dictionary with it:
.. code-block:: python
app.render(some_data, 'my_template.handlebars')
Helpers
^^^^^^^
Custom helper functions can easily be registered with the compiler via
``CementApp.Meta.handlebars_helpers`` and/or
``HandlebarsOutputHandler.Meta.helpers``.
.. code-block:: python
def my_custom_helper(this, arg1, arg2):
# do something with arg1 and arg2
if arg1 == arg2:
return True
else:
return False
class MyApp(CementApp):
class Meta:
label = 'myapp'
extensions = ['handlebars']
output_handler = 'handlebars'
handlebars_helpers = {
'myhelper' : my_custom_helper
}
# ...
You would then access this in your template as:
.. code-block:: console
This is my template
{{#if (myhelper this that)}}
This will only appear if myhelper returns True
{{/if}}
See the `Handlebars Documentation <https://github.com/wbond/pybars3>`_ for
more information on helpers.
Partials
^^^^^^^^
Though partials are supported by the library, there is no good way of
automatically loading them in the context and workflow of a typical Cement
application. Therefore, the extension needs a list of partial
template names to know what to preload, in order to make partials work.
Future versions will hopefully automate this.
Example:
.. code-block:: python
class MyApp(CementApp):
class Meta:
label = 'myapp'
extensions = ['handlebars']
output_handler = 'handlebars'
handlebars_partials = [
'header.bars',
'footer.bars',
]
Where ``header.bars`` and ``footer.bars`` are template names that will be
searched for, and loaded just like other templates loaded from template dirs.
These are then referenced in templates as:
.. code-block:: console
{{> "header.bars"}}
This is my template
{{> "footer.bars}}
See the `Handlebars Documentation <https://github.com/wbond/pybars3>`_ for
more information on partials.
"""
import sys
import pybars._compiler
from cement.core import output, handler
from cement.utils.misc import minimal_logger
# Monkey patch so we don't escape HTML (not clear how else to do this)
# See: https://github.com/wbond/pybars3/issues/25
original_prepare = pybars._compiler.prepare
def my_prepare(value, escape):
return original_prepare(value, False)
pybars._compiler.prepare = my_prepare
from pybars import Compiler # noqa
LOG = minimal_logger(__name__)
class HandlebarsOutputHandler(output.TemplateOutputHandler):
"""
This class implements the :ref:`IOutput <cement.core.output>`
interface. It provides text output from template and uses the
`Handlebars Templating Language <http://handlebarsjs.com/>`_ for Python
via the ``pybars`` library. Please see the developer documentation on
:ref:`Output Handling <dev_output_handling>`.
**Note** This extension has an external dependency on ``pybars3``. You
must include ``pybars3`` in your applications dependencies as Cement
explicitly does **not** include external dependencies for optional
extensions.
"""
class Meta:
"""Handler meta-data."""
interface = output.IOutput
label = 'handlebars'
#: Whether or not to include ``handlebars`` as an available to choice
#: to override the ``output_handler`` via command line options.
overridable = False
#: Custom helpers
helpers = {}
#: List of partials to preload
partials = []
def __init__(self, *args, **kw):
super(HandlebarsOutputHandler, self).__init__(*args, **kw)
self._raw_partials = {}
def _setup(self, app):
super(HandlebarsOutputHandler, self)._setup(app)
if hasattr(self.app._meta, 'handlebars_helpers'):
self._meta.helpers = self.app._meta.handlebars_helpers
if hasattr(self.app._meta, 'handlebars_partials'):
self._meta.partials = self.app._meta.handlebars_partials
for partial in self._meta.partials:
self._raw_partials[partial] = self.load_template(partial)
def _clean_content(self, content):
if sys.version_info[0] >= 3:
if not isinstance(content, str):
content = content.decode('utf-8')
else:
if not isinstance(content, unicode): # pragma: nocover # noqa
content = content.decode('utf-8') # pragma: nocover
return content
def render_content(self, data, content):
bars = Compiler()
content = bars.compile(self._clean_content(content))
# need to render partials
partials = {}
for key, val in self._raw_partials.items():
partials[key] = bars.compile(self._clean_content(val))
return content(data, helpers=self._meta.helpers, partials=partials)
def render(self, data, template):
"""
Take a data dictionary and render it using the given template file.
Required Arguments:
:param data: The data dictionary to render.
:keyword template: The path to the template, after the
``template_module`` or ``template_dirs`` prefix as defined in the
application.
:returns: str (the rendered template text)
"""
LOG.debug("rendering output using '%s' as a template." % template)
res = self.render_content(data, self.load_template(template))
return res
def load(app):
handler.register(HandlebarsOutputHandler)
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