Despite inheriting from the str type, every SafeString instance gains
an empty __dict__ due to the normal, expected behaviour of type
subclassing in Python.
Adding __slots__ to SafeData is necessary, because otherwise inheriting
from that (as SafeString does) will give it a __dict__ and negate the
benefit added by modifying SafeString.
Refs #7261 -- Made strings escaped by Django usable in third-party libs.
The changes in mark_safe and mark_for_escaping are straightforward. The
more tricky part is to handle correctly objects that implement __html__.
Historically escape() has escaped SafeData. Even if that doesn't seem a
good behavior, changing it would create security concerns. Therefore
support for __html__() was only added to conditional_escape() where this
concern doesn't exist.
Then using conditional_escape() instead of escape() in the Django
template engine makes it understand data escaped by other libraries.
Template filter |escape accounts for __html__() when it's available.
|force_escape forces the use of Django's HTML escaping implementation.
Here's why the change in render_value_in_context() is safe. Before Django
1.7 conditional_escape() was implemented as follows:
if isinstance(text, SafeData):
return text
else:
return escape(text)
render_value_in_context() never called escape() on SafeData. Therefore
replacing escape() with conditional_escape() doesn't change the
autoescaping logic as it was originally intended.
This change should be backported to Django 1.7 because it corrects a
feature added in Django 1.7.
Thanks mitsuhiko for the report.
mark_safe and mark_for_escaping should have been kept similar.
On Python 2 this change has no effect. On Python 3 it fixes the use case
shown in the regression test for mark_for_escaping, which used to raise
a TypeError. The regression test for mark_safe is just for completeness.
This reverts commit 2ee447fb5f.
That commit introduced a regression (#21882) and didn't really
do what it was supposed to: while it did delay the evaluation
of lazy objects passed to mark_safe(), they weren't actually
marked as such so they could end up being escaped twice.
Refs #21882.
The idea is that if an object implements __html__ which returns a string this is
used as HTML representation (eg: on escaping). If the object is a str or unicode
subclass and returns itself the object is a safe string type.
This is an updated patch based on jbalogh and ivank patches.
