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Fixed #14262 -- Added new assignment_tag as a simple way to assign th…

…e result of a template tag to a context variable. Thanks, Julien Phalip.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@16149 bcc190cf-cafb-0310-a4f2-bffc1f526a37
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commit 950e05c3ff5daa360c3bddb84831d40b167062f1 1 parent 8ce352c
@jezdez jezdez authored
View
60 django/template/base.py
@@ -901,6 +901,66 @@ def render(self, context):
else:
raise TemplateSyntaxError("Invalid arguments provided to simple_tag")
+ def assignment_tag(self, func=None, takes_context=None):
+ def dec(func):
+ params, xx, xxx, defaults = getargspec(func)
+ if takes_context:
+ if params[0] == 'context':
+ params = params[1:]
+ else:
+ raise TemplateSyntaxError("Any tag function decorated with takes_context=True must have a first argument of 'context'")
+
+ class AssignmentNode(Node):
+ def __init__(self, params_vars, target_var):
+ self.params_vars = map(Variable, params_vars)
+ self.target_var = target_var
+
+ def render(self, context):
+ resolved_vars = [var.resolve(context) for var in self.params_vars]
+ if takes_context:
+ func_args = [context] + resolved_vars
+ else:
+ func_args = resolved_vars
+ context[self.target_var] = func(*func_args)
+ return ''
+
+ def compile_func(parser, token):
+ bits = token.split_contents()
+ tag_name = bits[0]
+ bits = bits[1:]
+ params_max = len(params)
+ defaults_length = defaults and len(defaults) or 0
+ params_min = params_max - defaults_length
+ if (len(bits) < 2 or bits[-2] != 'as'):
+ raise TemplateSyntaxError(
+ "'%s' tag takes at least 2 arguments and the "
+ "second last argument must be 'as'" % tag_name)
+ params_vars = bits[:-2]
+ target_var = bits[-1]
+ if (len(params_vars) < params_min or
+ len(params_vars) > params_max):
+ if params_min == params_max:
+ raise TemplateSyntaxError(
+ "%s takes %s arguments" % (tag_name, params_min))
+ else:
+ raise TemplateSyntaxError(
+ "%s takes between %s and %s arguments"
+ % (tag_name, params_min, params_max))
+ return AssignmentNode(params_vars, target_var)
+
+ compile_func.__doc__ = func.__doc__
+ self.tag(getattr(func, "_decorated_function", func).__name__, compile_func)
+ return func
+
+ if func is None:
+ # @register.assignment_tag(...)
+ return dec
+ elif callable(func):
+ # @register.assignment_tag
+ return dec(func)
+ else:
+ raise TemplateSyntaxError("Invalid arguments provided to assignment_tag")
+
def inclusion_tag(self, file_name, context_class=Context, takes_context=False):
def dec(func):
params, xx, xxx, defaults = getargspec(func)
View
65 docs/howto/custom-template-tags.txt
@@ -681,7 +681,70 @@ Or, using decorator syntax::
return your_get_current_time_method(timezone, format_string)
For more information on how the ``takes_context`` option works, see the section
-on `inclusion tags`_.
+on :ref:`inclusion tags<howto-custom-template-tags-inclusion-tags>`.
+
+.. _howto-custom-template-tags-assignment-tags:
+
+Assignment tags
+~~~~~~~~~~~~~~~
+
+.. versionadded:: 1.4
+
+Another common type of template tag is the type that fetches some data and
+stores it in a context variable. To ease the creation of this type of tags,
+Django provides a helper function, ``assignment_tag``. This function works
+the same way as :ref:`simple_tag<howto-custom-template-tags-simple-tags>`,
+except that it stores the tag's result in a specified context variable instead
+of directly outputting it.
+
+Our earlier ``current_time`` function could thus be written like this:
+
+.. code-block:: python
+
+ def get_current_time(format_string):
+ return datetime.datetime.now().strftime(format_string)
+
+ register.assignment_tag(get_current_time)
+
+The decorator syntax also works:
+
+.. code-block:: python
+
+ @register.assignment_tag
+ def get_current_time(format_string):
+ ...
+
+You may then store the result in a template variable using the ``as`` argument
+followed by the variable name, and output it yourself where you see fit:
+
+.. code-block:: html+django
+
+ {% get_current_time "%Y-%m-%d %I:%M %p" as the_time %}
+ <p>The time is {{ the_time }}.</p>
+
+If your template tag needs to access the current context, you can use the
+``takes_context`` argument when registering your tag:
+
+.. code-block:: python
+
+ # The first argument *must* be called "context" here.
+ def get_current_time(context, format_string):
+ timezone = context['timezone']
+ return your_get_current_time_method(timezone, format_string)
+
+ register.assignment_tag(takes_context=True)(get_current_time)
+
+Or, using decorator syntax:
+
+.. code-block:: python
+
+ @register.assignment_tag(takes_context=True)
+ def get_current_time(context, format_string):
+ timezone = context['timezone']
+ return your_get_current_time_method(timezone, format_string)
+
+For more information on how the ``takes_context`` option works, see the section
+on :ref:`inclusion tags<howto-custom-template-tags-inclusion-tags>`.
.. _howto-custom-template-tags-inclusion-tags:
View
8 docs/releases/1.4.txt
@@ -52,6 +52,14 @@ documentation for :attr:`~django.contrib.admin.ModelAdmin.list_filter`.
A lazily evaluated version of :func:`django.core.urlresolvers.reverse` was
added to allow using URL reversals before the project's URLConf gets loaded.
+Assignment template tags
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+A new helper function,
+:ref:`assignment_tag<howto-custom-template-tags-assignment-tags>`, was added to
+``template.Library`` to ease the creation of template tags that store some
+data in a specified context variable.
+
.. _backwards-incompatible-changes-1.4:
Backwards incompatible changes in 1.4
View
53 tests/regressiontests/templates/custom.py
@@ -1,3 +1,5 @@
+from __future__ import with_statement
+
from django import template
from django.utils.unittest import TestCase
from templatetags import custom
@@ -102,3 +104,54 @@ def test_15070_use_l10n(self):
c.use_l10n = True
self.assertEquals(t.render(c).strip(), u'True')
+
+ def test_assignment_tags(self):
+ c = template.Context({'value': 42})
+
+ t = template.Template('{% load custom %}{% assignment_no_params as var %}The result is: {{ var }}')
+ self.assertEqual(t.render(c), u'The result is: assignment_no_params - Expected result')
+
+ t = template.Template('{% load custom %}{% assignment_one_param 37 as var %}The result is: {{ var }}')
+ self.assertEqual(t.render(c), u'The result is: assignment_one_param - Expected result: 37')
+
+ t = template.Template('{% load custom %}{% assignment_explicit_no_context 37 as var %}The result is: {{ var }}')
+ self.assertEqual(t.render(c), u'The result is: assignment_explicit_no_context - Expected result: 37')
+
+ t = template.Template('{% load custom %}{% assignment_no_params_with_context as var %}The result is: {{ var }}')
+ self.assertEqual(t.render(c), u'The result is: assignment_no_params_with_context - Expected result (context value: 42)')
+
+ t = template.Template('{% load custom %}{% assignment_params_and_context 37 as var %}The result is: {{ var }}')
+ self.assertEqual(t.render(c), u'The result is: assignment_params_and_context - Expected result (context value: 42): 37')
+
+ self.assertRaisesRegexp(template.TemplateSyntaxError,
+ "'assignment_one_param' tag takes at least 2 arguments and the second last argument must be 'as'",
+ template.Template, '{% load custom %}{% assignment_one_param 37 %}The result is: {{ var }}')
+
+ self.assertRaisesRegexp(template.TemplateSyntaxError,
+ "'assignment_one_param' tag takes at least 2 arguments and the second last argument must be 'as'",
+ template.Template, '{% load custom %}{% assignment_one_param 37 as %}The result is: {{ var }}')
+
+ self.assertRaisesRegexp(template.TemplateSyntaxError,
+ "'assignment_one_param' tag takes at least 2 arguments and the second last argument must be 'as'",
+ template.Template, '{% load custom %}{% assignment_one_param 37 ass var %}The result is: {{ var }}')
+
+ def test_assignment_tag_registration(self):
+ # Test that the decorators preserve the decorated function's docstring, name and attributes.
+ self.verify_tag(custom.assignment_no_params, 'assignment_no_params')
+ self.verify_tag(custom.assignment_one_param, 'assignment_one_param')
+ self.verify_tag(custom.assignment_explicit_no_context, 'assignment_explicit_no_context')
+ self.verify_tag(custom.assignment_no_params_with_context, 'assignment_no_params_with_context')
+ self.verify_tag(custom.assignment_params_and_context, 'assignment_params_and_context')
+
+ def test_assignment_tag_missing_context(self):
+ # That the 'context' parameter must be present when takes_context is True
+ def an_assignment_tag_without_parameters(arg):
+ """Expected __doc__"""
+ return "Expected result"
+
+ register = template.Library()
+ decorator = register.assignment_tag(takes_context=True)
+
+ self.assertRaisesRegexp(template.TemplateSyntaxError,
+ "Any tag function decorated with takes_context=True must have a first argument of 'context'",
+ decorator, an_assignment_tag_without_parameters)
View
30 tests/regressiontests/templates/templatetags/custom.py
@@ -84,3 +84,33 @@ def use_l10n(context):
@register.inclusion_tag('test_incl_tag_use_l10n.html', takes_context=True)
def inclusion_tag_use_l10n(context):
return {}
+
+@register.assignment_tag
+def assignment_no_params():
+ """Expected assignment_no_params __doc__"""
+ return "assignment_no_params - Expected result"
+assignment_no_params.anything = "Expected assignment_no_params __dict__"
+
+@register.assignment_tag
+def assignment_one_param(arg):
+ """Expected assignment_one_param __doc__"""
+ return "assignment_one_param - Expected result: %s" % arg
+assignment_one_param.anything = "Expected assignment_one_param __dict__"
+
+@register.assignment_tag(takes_context=False)
+def assignment_explicit_no_context(arg):
+ """Expected assignment_explicit_no_context __doc__"""
+ return "assignment_explicit_no_context - Expected result: %s" % arg
+assignment_explicit_no_context.anything = "Expected assignment_explicit_no_context __dict__"
+
+@register.assignment_tag(takes_context=True)
+def assignment_no_params_with_context(context):
+ """Expected assignment_no_params_with_context __doc__"""
+ return "assignment_no_params_with_context - Expected result (context value: %s)" % context['value']
+assignment_no_params_with_context.anything = "Expected assignment_no_params_with_context __dict__"
+
+@register.assignment_tag(takes_context=True)
+def assignment_params_and_context(context, arg):
+ """Expected assignment_params_and_context __doc__"""
+ return "assignment_params_and_context - Expected result (context value: %s): %s" % (context['value'], arg)
+assignment_params_and_context.anything = "Expected assignment_params_and_context __dict__"
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