1 files changed, 54 insertions, 0 deletions
diff --git a/docs/examples/cache_extension.py b/docs/examples/cache_extension.py
new file mode 100644
index 0000000..387cd46
--- /dev/null
+++ b/docs/examples/cache_extension.py
@@ -0,0 +1,54 @@
+from jinja2 import nodes
+from jinja2.ext import Extension
+
+
+class FragmentCacheExtension(Extension):
+    # a set of names that trigger the extension.
+    tags = {"cache"}
+
+    def __init__(self, environment):
+        super(FragmentCacheExtension, self).__init__(environment)
+
+        # add the defaults to the environment
+        environment.extend(fragment_cache_prefix="", fragment_cache=None)
+
+    def parse(self, parser):
+        # the first token is the token that started the tag.  In our case
+        # we only listen to ``'cache'`` so this will be a name token with
+        # `cache` as value.  We get the line number so that we can give
+        # that line number to the nodes we create by hand.
+        lineno = next(parser.stream).lineno
+
+        # now we parse a single expression that is used as cache key.
+        args = [parser.parse_expression()]
+
+        # if there is a comma, the user provided a timeout.  If not use
+        # None as second parameter.
+        if parser.stream.skip_if("comma"):
+            args.append(parser.parse_expression())
+        else:
+            args.append(nodes.Const(None))
+
+        # now we parse the body of the cache block up to `endcache` and
+        # drop the needle (which would always be `endcache` in that case)
+        body = parser.parse_statements(["name:endcache"], drop_needle=True)
+
+        # now return a `CallBlock` node that calls our _cache_support
+        # helper method on this extension.
+        return nodes.CallBlock(
+            self.call_method("_cache_support", args), [], [], body
+        ).set_lineno(lineno)
+
+    def _cache_support(self, name, timeout, caller):
+        """Helper callback."""
+        key = self.environment.fragment_cache_prefix + name
+
+        # try to load the block from the cache
+        # if there is no fragment in the cache, render it and store
+        # it in the cache.
+        rv = self.environment.fragment_cache.get(key)
+        if rv is not None:
+            return rv
+        rv = caller()
+        self.environment.fragment_cache.add(key, rv, timeout)
+        return rv