57 lines
2.1 KiB
Python
57 lines
2.1 KiB
Python
from jinja2 import nodes
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from jinja2.ext import Extension
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class FragmentCacheExtension(Extension):
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# a set of names that trigger the extension.
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tags = set(['cache'])
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def __init__(self, environment):
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super(FragmentCacheExtension, self).__init__(environment)
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# add the defaults to the environment
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environment.extend(
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fragment_cache_prefix='',
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fragment_cache=None
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)
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def parse(self, parser):
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# the first token is the token that started the tag. In our case
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# we only listen to ``'cache'`` so this will be a name token with
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# `cache` as value. We get the line number so that we can give
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# that line number to the nodes we create by hand.
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lineno = parser.stream.next().lineno
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# now we parse a single expression that is used as cache key.
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args = [parser.parse_expression()]
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# if there is a comma, the user provided a timeout. If not use
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# None as second parameter.
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if parser.stream.skip_if('comma'):
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args.append(parser.parse_expression())
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else:
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args.append(nodes.Const(None))
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# now we parse the body of the cache block up to `endcache` and
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# drop the needle (which would always be `endcache` in that case)
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body = parser.parse_statements(['name:endcache'], drop_needle=True)
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# now return a `CallBlock` node that calls our _cache_support
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# helper method on this extension.
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return nodes.CallBlock(self.call_method('_cache_support', args),
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[], [], body).set_lineno(lineno)
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def _cache_support(self, name, timeout, caller):
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"""Helper callback."""
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key = self.environment.fragment_cache_prefix + name
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# try to load the block from the cache
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# if there is no fragment in the cache, render it and store
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# it in the cache.
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rv = self.environment.fragment_cache.get(key)
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if rv is not None:
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return rv
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rv = caller()
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self.environment.fragment_cache.add(key, rv, timeout)
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return rv
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