django.utils.decorators.decorator_from_middleware doesn't work with parameters

Duplicate of #1047.

Possible solution, keeping backward compatibility:

--- django/utils/decorators.py  (revision 4490)
+++ django/utils/decorators.py  (working copy)
@@ -30,4 +30,12 @@
                     return result
             return response
         return _wrapped_view
+
+    def _true_24_decorator(*args, **kwargs):
+        def _decorator(f):
+            return _decorator_from_middleware(f, *args, **kwargs)
+        return _decorator
+
+    _decorator_from_middleware.decorator = _true_24_decorator
+
     return _decorator_from_middleware

Usage:

@cache_page.decorator(60)
def my_cool_view(request):
    # cool processing

If it's ok, then feel free to rename the "decorator" attribute to something nice and short enough to type.

Usage is in the comments

#2567 and #3967 marked as duplicates.

Decorators that take arguments need to be functions that return a function that returns a decorator. See these docs for info:

• http://www.python.org/doc/2.4.4/whatsnew/node6.html
• http://www.python.org/dev/peps/pep-0318/
• http://mail.python.org/pipermail/python-dev/2004-September/048874.html

From PEP 318:

The current syntax also allows decorator declarations to call a function that returns a decorator:

@decomaker(argA, argB, ...)
def func(arg1, arg2, ...):
    pass

This is equivalent to:

func = decomaker(argA, argB, ...)(func)

The cache_page decorator appears to be the only one using decorator_from_middleware that also takes arguments, but decorator_from_middleware does not handle decorators that take arguments.

Also the cache documentation is incorrect, because instead of:

slashdot_this = cache_page(slashdot_this, 60 * 15)

it should be

slashdot_this = cache_page(60 * 15)(slashdot_this)

Description of attached patch:

• Added a decorator_with_arguments_from_middleware function for generating functions that generate decorators from middleware classes whose constructors take arguments.
• Factored out the inner decorator function from in decorator_from_middleware into a make_decorator_from_middleware function that generates decorators from middleware classes.
• Changed the cache_page decorator to use decorator_with_arguments_from_middleware since it takes parameters.
• Added CACHE_MIDDLEWARE_SECONDS to the global settings. You will get an error when using cache_page without this setting since it is using the CacheMiddleware, which uses CACHE_MIDDLEWARE_SECONDS.
• Documented the fact that cache_page can take more than one argument.

I should note that the patch is backwards incompatible with people using the cache_page decorator as documented:

slashdot_this = cache_page(slashdot_this, 60 * 15)

Would be nice to avoid the backwards incompatibility if we could. A new name for cache_page would be one way (then cache_page() would work as it does now and the new named function would be the new decorator).

Most of the rest looks great. Will probably give decorator_with_arguments_from_middleware a shorter name to avoid inflicting RSI on the world's population, but that's only cosmetic.

(In [5618]) Added CACHE_MIDDLEWARE_SECONDS to global settings and documentation (it's used by the cache middleware). Refs #1015.

(In [5619]) Fixed #1015 -- Fixed decorator_from_middleware to return a real decorator even when arguments are given. This looks a bit ugly, but it's fully backwards compatible and all the extra work is done at import time, so it shouldn't have any real performance impact.