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from __future__ import annotations
from .mixins import ImmutableDictMixin
from .mixins import UpdateDictMixin
def cache_control_property(key, empty, type):
"""Return a new property object for a cache header. Useful if you
want to add support for a cache extension in a subclass.
.. versionchanged:: 2.0
Renamed from ``cache_property``.
"""
return property(
lambda x: x._get_cache_value(key, empty, type),
lambda x, v: x._set_cache_value(key, v, type),
lambda x: x._del_cache_value(key),
f"accessor for {key!r}",
)
class _CacheControl(UpdateDictMixin, dict):
"""Subclass of a dict that stores values for a Cache-Control header. It
has accessors for all the cache-control directives specified in RFC 2616.
The class does not differentiate between request and response directives.
Because the cache-control directives in the HTTP header use dashes the
python descriptors use underscores for that.
To get a header of the :class:`CacheControl` object again you can convert
the object into a string or call the :meth:`to_header` method. If you plan
to subclass it and add your own items have a look at the sourcecode for
that class.
.. versionchanged:: 2.1.0
Setting int properties such as ``max_age`` will convert the
value to an int.
.. versionchanged:: 0.4
Setting `no_cache` or `private` to boolean `True` will set the implicit
none-value which is ``*``:
>>> cc = ResponseCacheControl()
>>> cc.no_cache = True
>>> cc
<ResponseCacheControl 'no-cache'>
>>> cc.no_cache
'*'
>>> cc.no_cache = None
>>> cc
<ResponseCacheControl ''>
In versions before 0.5 the behavior documented here affected the now
no longer existing `CacheControl` class.
"""
no_cache = cache_control_property("no-cache", "*", None)
no_store = cache_control_property("no-store", None, bool)
max_age = cache_control_property("max-age", -1, int)
no_transform = cache_control_property("no-transform", None, None)
def __init__(self, values=(), on_update=None):
dict.__init__(self, values or ())
self.on_update = on_update
self.provided = values is not None
def _get_cache_value(self, key, empty, type):
"""Used internally by the accessor properties."""
if type is bool:
return key in self
if key in self:
value = self[key]
if value is None:
return empty
elif type is not None:
try:
value = type(value)
except ValueError:
pass
return value
return None
def _set_cache_value(self, key, value, type):
"""Used internally by the accessor properties."""
if type is bool:
if value:
self[key] = None
else:
self.pop(key, None)
else:
if value is None:
self.pop(key, None)
elif value is True:
self[key] = None
else:
if type is not None:
self[key] = type(value)
else:
self[key] = value
def _del_cache_value(self, key):
"""Used internally by the accessor properties."""
if key in self:
del self[key]
def to_header(self):
"""Convert the stored values into a cache control header."""
return http.dump_header(self)
def __str__(self):
return self.to_header()
def __repr__(self):
kv_str = " ".join(f"{k}={v!r}" for k, v in sorted(self.items()))
return f"<{type(self).__name__} {kv_str}>"
cache_property = staticmethod(cache_control_property)
class RequestCacheControl(ImmutableDictMixin, _CacheControl):
"""A cache control for requests. This is immutable and gives access
to all the request-relevant cache control headers.
To get a header of the :class:`RequestCacheControl` object again you can
convert the object into a string or call the :meth:`to_header` method. If
you plan to subclass it and add your own items have a look at the sourcecode
for that class.
.. versionchanged:: 2.1.0
Setting int properties such as ``max_age`` will convert the
value to an int.
.. versionadded:: 0.5
In previous versions a `CacheControl` class existed that was used
both for request and response.
"""
max_stale = cache_control_property("max-stale", "*", int)
min_fresh = cache_control_property("min-fresh", "*", int)
only_if_cached = cache_control_property("only-if-cached", None, bool)
class ResponseCacheControl(_CacheControl):
"""A cache control for responses. Unlike :class:`RequestCacheControl`
this is mutable and gives access to response-relevant cache control
headers.
To get a header of the :class:`ResponseCacheControl` object again you can
convert the object into a string or call the :meth:`to_header` method. If
you plan to subclass it and add your own items have a look at the sourcecode
for that class.
.. versionchanged:: 2.1.1
``s_maxage`` converts the value to an int.
.. versionchanged:: 2.1.0
Setting int properties such as ``max_age`` will convert the
value to an int.
.. versionadded:: 0.5
In previous versions a `CacheControl` class existed that was used
both for request and response.
"""
public = cache_control_property("public", None, bool)
private = cache_control_property("private", "*", None)
must_revalidate = cache_control_property("must-revalidate", None, bool)
proxy_revalidate = cache_control_property("proxy-revalidate", None, bool)
s_maxage = cache_control_property("s-maxage", None, int)
immutable = cache_control_property("immutable", None, bool)
# circular dependencies
from .. import http
|
