Micro-library to easily write custom Django template tags
Project description
django-tag-parser
A micro-library to easily write custom Django template tags.
Features:
Functions to parse tags, especially: “args”, “kwargs”, and “as varname” syntax.
Real OOP classes to write custom inclusion tags.
Functions:
parse_token_kwargs: split a token into the tag name, args and kwargs.
parse_as_var: extract the “as varname” from a token.
Decorators:
@template_tag: register a class with a parse(parser, token) method as template tag.
Base classes (in tag_parser.basetags):
BaseNode: A template Node object which features some basic parsing abilities.
BaseInclusionNode: a Node that has inclusion_tag like behaviour, but allows to override the template_name dynamically.
BaseAssignmentOrInclusionNode: a class that allows a {% get_items template="..." %} and {% get_items as var %} syntax.
The base classes allows to implement @register.simple_tag, @register.inclusion_tag and @register.assignment_tag like functionalities, while still leaving room to extend the parsing, rendering or syntax validation. For example, not all arguments need to be seen as template variables, filters or literal keywords.
Installation
First install the module, preferably in a virtual environment. It can be installed from PyPI:
pip install django-tag-parser
Or the current folder can be installed:
pip install .
Examples
In your template tags library:
from django.template import Library from tag_parser import template_tag from tag_parser.basetags import BaseNode, BaseInclusionNode register = Library()
Arguments and keyword arguments
To parse a syntax like:
{% my_tag "arg1" keyword1="bar" keyword2="foo" %}
use:
@template_tag(register, 'my_tag')
class MyTagNode(BaseNode):
max_args = 1
allowed_kwargs = ('keyword1', 'keyword2',)
def render_tag(self, context, *tag_args, **tag_kwargs):
return "Tag Output"
Custom parsing
With a standard Node class, it’s easier to implement custom syntax. For example, to parse:
{% getfirstof val1 val2 as val3 %}
use:
@template_tag(register, 'getfirstof')
class GetFirstOfNode(Node):
def __init__(self, options, as_var):
self.options = options # list of FilterExpression nodes.
self.as_var = as_var
@classmethod
def parse(cls, parser, token):
bits, as_var = parse_as_var(parser, token)
tag_name, options, _ = parse_token_kwargs(parser, bits, allowed_kwargs=())
if as_var is None or not choices:
raise TemplateSyntaxError("Expected syntax: {{% {0} val1 val2 as val %}}".format(tag_name))
return cls(options, as_var)
def render(self, context):
value = None
for filterexpr in self.options:
# The ignore_failures argument prevents that the value becomes TEMPLATE_STRING_IF_INVALID.
value = filterexpr.resolve(context, ignore_failures=True)
if value is not None:
break
context[self.as_var] = value
return ''
Contributing
This module is designed to be generic. In case there is anything you didn’t like about it, or think it’s not flexible enough, please let us know. We’d love to improve it!
If you have any other valuable contribution, suggestion or idea, please let us know as well because we will look into it. Pull requests are welcome too. :-)
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