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from __future__ import annotations
import collections.abc as cabc
import typing as t
from inspect import cleandoc
from .mixins import ImmutableDictMixin
from .structures import CallbackDict
def cache_control_property(
key: str, empty: t.Any, type: type[t.Any] | None, *, doc: str | None = None
) -> t.Any:
"""Return a new property object for a cache header. Useful if you
want to add support for a cache extension in a subclass.
:param key: The attribute name present in the parsed cache-control header dict.
:param empty: The value to use if the key is present without a value.
:param type: The type to convert the string value to instead of a string. If
conversion raises a ``ValueError``, the returned value is ``None``.
:param doc: The docstring for the property. If not given, it is generated
based on the other params.
.. versionchanged:: 3.1
Added the ``doc`` param.
.. versionchanged:: 2.0
Renamed from ``cache_property``.
"""
if doc is None:
parts = [f"The ``{key}`` attribute."]
if type is bool:
parts.append("A ``bool``, either present or not.")
else:
if type is None:
parts.append("A ``str``,")
else:
parts.append(f"A ``{type.__name__}``,")
if empty is not None:
parts.append(f"``{empty!r}`` if present with no value,")
parts.append("or ``None`` if not present.")
doc = " ".join(parts)
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),
doc=cleandoc(doc),
)
class _CacheControl(CallbackDict[str, t.Optional[str]]):
"""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:: 3.1
Dict values are always ``str | None``. Setting properties will
convert the value to a string. Setting a non-bool property to
``False`` is equivalent to setting it to ``None``. Getting typed
properties will return ``None`` if conversion raises
``ValueError``, rather than the string.
.. versionchanged:: 2.1
Setting int properties such as ``max_age`` will convert the
value to an int.
.. versionchanged:: 0.4
Setting ``no_cache`` or ``private`` to ``True`` will set the
implicit value ``"*"``.
"""
no_store: bool = cache_control_property("no-store", None, bool)
max_age: int | None = cache_control_property("max-age", None, int)
no_transform: bool = cache_control_property("no-transform", None, bool)
stale_if_error: int | None = cache_control_property("stale-if-error", None, int)
def __init__(
self,
values: cabc.Mapping[str, t.Any] | cabc.Iterable[tuple[str, t.Any]] | None = (),
on_update: cabc.Callable[[_CacheControl], None] | None = None,
):
super().__init__(values, on_update)
self.provided = values is not None
def _get_cache_value(
self, key: str, empty: t.Any, type: type[t.Any] | None
) -> t.Any:
"""Used internally by the accessor properties."""
if type is bool:
return key in self
if key not in self:
return None
if (value := self[key]) is None:
return empty
if type is not None:
try:
value = type(value)
except ValueError:
return None
return value
def _set_cache_value(
self, key: str, value: t.Any, type: type[t.Any] | None
) -> None:
"""Used internally by the accessor properties."""
if type is bool:
if value:
self[key] = None
else:
self.pop(key, None)
elif value is None or value is False:
self.pop(key, None)
elif value is True:
self[key] = None
else:
if type is not None:
value = type(value)
self[key] = str(value)
def _del_cache_value(self, key: str) -> None:
"""Used internally by the accessor properties."""
if key in self:
del self[key]
def to_header(self) -> str:
"""Convert the stored values into a cache control header."""
return http.dump_header(self)
def __str__(self) -> str:
return self.to_header()
def __repr__(self) -> str:
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[str, t.Optional[str]], _CacheControl): # type: ignore[misc]
"""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:: 3.1
Dict values are always ``str | None``. Setting properties will
convert the value to a string. Setting a non-bool property to
``False`` is equivalent to setting it to ``None``. Getting typed
properties will return ``None`` if conversion raises
``ValueError``, rather than the string.
.. versionchanged:: 3.1
``max_age`` is ``None`` if present without a value, rather
than ``-1``.
.. versionchanged:: 3.1
``no_cache`` is a boolean, it is ``True`` instead of ``"*"``
when present.
.. versionchanged:: 3.1
``max_stale`` is ``True`` if present without a value, rather
than ``"*"``.
.. versionchanged:: 3.1
``no_transform`` is a boolean. Previously it was mistakenly
always ``None``.
.. versionchanged:: 3.1
``min_fresh`` is ``None`` if present without a value, rather
than ``"*"``.
.. versionchanged:: 2.1
Setting int properties such as ``max_age`` will convert the
value to an int.
.. versionadded:: 0.5
Response-only properties are not present on this request class.
"""
no_cache: bool = cache_control_property("no-cache", None, bool)
max_stale: int | t.Literal[True] | None = cache_control_property(
"max-stale",
True,
int,
)
min_fresh: int | None = cache_control_property("min-fresh", None, int)
only_if_cached: bool = 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:: 3.1
Dict values are always ``str | None``. Setting properties will
convert the value to a string. Setting a non-bool property to
``False`` is equivalent to setting it to ``None``. Getting typed
properties will return ``None`` if conversion raises
``ValueError``, rather than the string.
.. versionchanged:: 3.1
``no_cache`` is ``True`` if present without a value, rather than
``"*"``.
.. versionchanged:: 3.1
``private`` is ``True`` if present without a value, rather than
``"*"``.
.. versionchanged:: 3.1
``no_transform`` is a boolean. Previously it was mistakenly
always ``None``.
.. versionchanged:: 3.1
Added the ``must_understand``, ``stale_while_revalidate``, and
``stale_if_error`` properties.
.. versionchanged:: 2.1.1
``s_maxage`` converts the value to an int.
.. versionchanged:: 2.1
Setting int properties such as ``max_age`` will convert the
value to an int.
.. versionadded:: 0.5
Request-only properties are not present on this response class.
"""
no_cache: str | t.Literal[True] | None = cache_control_property(
"no-cache", True, None
)
public: bool = cache_control_property("public", None, bool)
private: str | t.Literal[True] | None = cache_control_property(
"private", True, None
)
must_revalidate: bool = cache_control_property("must-revalidate", None, bool)
proxy_revalidate: bool = cache_control_property("proxy-revalidate", None, bool)
s_maxage: int | None = cache_control_property("s-maxage", None, int)
immutable: bool = cache_control_property("immutable", None, bool)
must_understand: bool = cache_control_property("must-understand", None, bool)
stale_while_revalidate: int | None = cache_control_property(
"stale-while-revalidate", None, int
)
# circular dependencies
from .. import http
|