format_html not working with lazy objects on jython

[andreas@…]

django.utils.html.format_html does not convert lazy string objects to unicode on jython. E.g. the hidden csrf_token field looks like follows:

<input type="hidden" name="csrfmiddlewaretoken" value="&lt;django.utils.functional.__proxy__ object at 0x1c7&gt;">

I attached a patch that fixes this bug.

[Florian Apolloner]

Is that only an issue on jython or on python too?

[andreas@…]

As far as I can see, it is only an issue on jython. I guess there is a difference in the behaviour of the string.format method. However, '%s' place holders are working fine with lazy string objects.

[Aymeric Augustin]

We should review carefully what the expected type and what the actual type are (str or unicode?), and make sure this is the correct level to fix the problem. If we're indeed relying on an implicit cast, and that trips up Jython, we should make it explicit. (str is unicode-based on Jython and that could explain the problem.)

I would also like to see a test that fails on CPython; without such a test we could easily reintroduce this problem in the future.

Minor comment on the patch: args_safe should use a list comprehension rather than map/lambda.

[andreas@…]

I attached a new version of the patch that is using a list comprehension instead of a map+lambda expression. Unfortunately I was not able to write a test that reproduces the Jython behaviour on CPython.

[andreas@…]

I was able to fix the problem on a lower level, by assigning the __text_cast method not only on the __unicode__ method of the Promise class, but also on the __str__ method. But I am not sure if that is the right thing to do.

[Baptiste Mispelon]

This looks like it might be related to #20221.

Can you try applying the patch I made for it [1] and telling me if the problem is still there?

Thanks.

[1] ​https://github.com/django/django/pull/1007

[andreas@…]

Unfortunately your patch does not solve the problem with jython.

[Tim Graham]

​django-jython has been updated to work with Django 1.7. I'd think we would have heard about this issue if it were still a problem. Please reopen with more details if it can still be reproduced.