Allow mark_safe() to be used as a decorator

[matehat]

I think the two safety markers located in django.utils.safestring could be improved a bit to help DRYing up a redundant situation. Say some function of a model or whatever class instance is often used in templates and instead of applying the safe filter to it everywhere it appears in the template code, the returned value is marked as safe. Now the following pattern can be DRYed up:

def some_method(self, arg):
  if arg == 1:
    return mark_safe(some_tags)
  elif arg == 2:
    return mark_safe(some_other_tags)
  elif arg == 3:
    return mark_safe(some_third_tags)

Sure there are better ways to organize this type of pattern but it shows my point. Instead of appying the marker everywhere data is returned, it could be used as a decorator on the whole method:

@mark_safe
def some_method(self, arg):
  if arg == 1:
    return some_tags
  elif arg == 2:
    return some_other_tags
  elif arg == 3:
    return some_third_tags

Anyway, I made the necessary patch, so take a look at it! The same is applied to the mark_for_escaping method for the same reasons.

[Malcolm Tredinnick]

This isn't a bad idea. There are some improvements that jump out at me from reading the patch, however:

1. Code must be Python 2.3 compatible, which means you can't use a decorator in any of this code (you're using one for one of the nested functions).
2. Don't worry about allowing the case of @mark_safe(). That's just poor style, since the decorator/function never takes any arguments. People can get by with only writing @mark_safe. That removes the need for s=None, too, which avoids accidental errors.
3. Patch needs to include documentation changes to describe the new usage.
4. Patch needs to include test changes, so that we can verify it continues to keep on working in the future.

[matehat]

The new patch includes fixes for python 2.3 compatibility and a test case for testing escaping behavior (though for a unknown reason, the file's content doesn't show up in trac ... I can only see its content when downloading it ...) I'm still unsure where I should put the documentation for this: in 'Custom template tags' (It's not quite designed for this) or in '(Template) Syntax overview' (though turning autoescaping off is only mentioned there for the template side of coding, i.e. for template designers).

[dc]

Maybe offtopic, but in your case better use function with one exit point:

def some_method(self, arg):
  if arg == 1:
    tags = some_tags
  elif arg == 2:
    tags = some_other_tags
  elif arg == 3:
    tags = some_third_tags
  return mark_safe(tags)

[matehat]

Yes, of course :P, I made up a simplistic situation that is rather a 'reduced' version of more complex cases, where a very complicated processing sometimes happen. Of course it can always be rearranged the way you suggested, but that can also make things less straightfoward.

[matehat]

Sorry about the long time in adding patch to documentation for using mark_safe and mark_for_escaping as decorators. The new patch includes tests and documentation.

[matehat]

New patch for regressiontests, documentation and django.utils.safestring

[Aymeric Augustin]

Change UI/UX from NULL to False.

[Petr Dlouhý]

Where got this stuck? Is there any problem with the patch?

[Tim Graham]

The patch is 7 years old, so needs to be updated to apply cleanly to trunk and conform to the guidelines of the PatchReviewChecklist.

I'd also suggest to drop the enhancement for mark_for_escaping() as that function is under consideration for deprecation in #24046.

[Susan Tan]

​https://github.com/django/django/pull/6390 is the github pull request.

[Scott Vitale]

Talked to susan at Pycon 2016 and created a new PR to incorporate the comments from her original work. New PR here: ​https://github.com/django/django/pull/6706

[Tim Graham]

Left comments for improvement on the PR. Please uncheck "Patch needs improvement" after updating.

[Tim Graham <timograham@…>]

In be729b6:

Fixed #10107 -- Allowed using mark_safe() as a decorator.

Thanks ArcTanSusan for the initial patch.