94 lines
3.3 KiB
Python
94 lines
3.3 KiB
Python
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from django.core.cache import InvalidCacheBackendError, caches
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from django.core.cache.utils import make_template_fragment_key
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from django.template import (
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Library, Node, TemplateSyntaxError, VariableDoesNotExist,
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)
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register = Library()
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class CacheNode(Node):
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def __init__(self, nodelist, expire_time_var, fragment_name, vary_on, cache_name):
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self.nodelist = nodelist
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self.expire_time_var = expire_time_var
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self.fragment_name = fragment_name
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self.vary_on = vary_on
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self.cache_name = cache_name
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def render(self, context):
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try:
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expire_time = self.expire_time_var.resolve(context)
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except VariableDoesNotExist:
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raise TemplateSyntaxError('"cache" tag got an unknown variable: %r' % self.expire_time_var.var)
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if expire_time is not None:
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try:
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expire_time = int(expire_time)
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except (ValueError, TypeError):
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raise TemplateSyntaxError('"cache" tag got a non-integer timeout value: %r' % expire_time)
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if self.cache_name:
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try:
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cache_name = self.cache_name.resolve(context)
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except VariableDoesNotExist:
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raise TemplateSyntaxError('"cache" tag got an unknown variable: %r' % self.cache_name.var)
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try:
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fragment_cache = caches[cache_name]
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except InvalidCacheBackendError:
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raise TemplateSyntaxError('Invalid cache name specified for cache tag: %r' % cache_name)
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else:
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try:
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fragment_cache = caches['template_fragments']
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except InvalidCacheBackendError:
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fragment_cache = caches['default']
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vary_on = [var.resolve(context) for var in self.vary_on]
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cache_key = make_template_fragment_key(self.fragment_name, vary_on)
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value = fragment_cache.get(cache_key)
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if value is None:
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value = self.nodelist.render(context)
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fragment_cache.set(cache_key, value, expire_time)
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return value
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@register.tag('cache')
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def do_cache(parser, token):
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"""
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This will cache the contents of a template fragment for a given amount
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of time.
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Usage::
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{% load cache %}
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{% cache [expire_time] [fragment_name] %}
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.. some expensive processing ..
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{% endcache %}
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This tag also supports varying by a list of arguments::
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{% load cache %}
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{% cache [expire_time] [fragment_name] [var1] [var2] .. %}
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.. some expensive processing ..
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{% endcache %}
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Optionally the cache to use may be specified thus::
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{% cache .... using="cachename" %}
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Each unique set of arguments will result in a unique cache entry.
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"""
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nodelist = parser.parse(('endcache',))
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parser.delete_first_token()
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tokens = token.split_contents()
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if len(tokens) < 3:
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raise TemplateSyntaxError("'%r' tag requires at least 2 arguments." % tokens[0])
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if len(tokens) > 3 and tokens[-1].startswith('using='):
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cache_name = parser.compile_filter(tokens[-1][len('using='):])
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tokens = tokens[:-1]
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else:
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cache_name = None
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return CacheNode(
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nodelist, parser.compile_filter(tokens[1]),
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tokens[2], # fragment_name can't be a variable.
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[parser.compile_filter(t) for t in tokens[3:]],
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cache_name,
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)
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