Re: Should reverse() return a Unicode string?

[Jon Dufresne]

On Fri, Sep 19, 2014 at 5:13 AM, Tom Christie  wrote:
> One point of clarity is that we ought to return the same type for each of
> `reverse`, `request.path`, `request.get_full_path`, `request.path_info`, and
> the values in the `request.GET` dictionary. Given that, the answer is
> clearly "it should be a string".

>From my testing, these are all returning text strings except `reverse()`.

The pull request for the reverse() fix can be found here:


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Re: Should reverse() return a Unicode string?

[Tom Christie]

One point of clarity is that we ought to return the same type for each of 
`reverse`, `request.path`, `request.get_full_path`, `request.path_info`, 
and the values in the `request.GET` dictionary. Given that, the answer is 
clearly "it should be a string".

It's also a little unclear to me what type is currently expected from 
values in the `request.META` dictionary. I believe that the `HTTP_*` keys 
currently return byte objects, but it's not documented, or clear to me if 
that's consistently true.

On Thursday, 18 September 2014 22:11:39 UTC+1, Carl Meyer wrote:
>
> Hi Jon, 
>
> On 09/18/2014 02:01 PM, Jon Dufresne wrote: 
> > In my Django application, I'm making a strong attempt to always deal 
> > with Unicode strings at the application layer. Byte strings are only 
> > handled at the protocol layer -- sending data out on the "wire". If my 
> > application tests if an object is a string, I'll use isinstance(obj, 
> > unicode) (Python2). 
> > 
> > One gotcha that I noticed is that reverse() will always return a byte 
> > string. Tracing this through the code, I see this happens during the 
> > call to iri_to_uri(), as this function creates a string consisting 
> > only of ASCII characters, other characters are escaped. 
> > 
> > Now, reverse() is often used to grab a URL and handle it at the 
> > application layer. It is not reserved only for the protocol layer. An 
> > example would be presenting a URL inside a HTML template, (as an href 
> > or as text), mail, or JSON. 
> > 
> > In my opinion, reverse() should return a Unicode string, even if that 
> > string consists only of ASCII characters. It is not until the string 
> > hits the wire that it ought to be forced to bytes. 
> > 
> > To verify this, I have created a unit test that I placed in 
> > "urlpatterns_reverse.tests.URLPatternReverse" to demonstrate this is 
> > at the Django layer. 
> > 
> > def test_reverse_unicode(self): 
> > name, expected, args, kwargs = test_data[0] 
> > self.assertIsInstance( 
> > reverse(name, args=args, kwargs=kwargs), 
> >     six.text_type) 
> > 
> > What do you think? If others agree, I can file a bug and create a pull 
> > request to fix this. 
>
> It makes sense to me that `reverse()` should return a text (unicode) 
> string. A URL may be "just bytes" on the network, but within the Django 
> context it is clearly text. 
>
> I'm a bit concerned about the backwards-compatibility implications, 
> particularly for Python 3 projects where `bytes` and `str` don't 
> silently interoperate. It would be really interesting to hear if anyone 
> on this list has a real-world Python 3 Django project handy and could 
> test the impact of this change. 
>
> Carl 
>

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Re: Should reverse() return a Unicode string?

[Wim Feijen]

Please do. :) 

- Wim

On Thursday, 18 September 2014 22:01:21 UTC+2, Jon Dufresne wrote:
>
> What do you think? If others agree, I can file a bug and create a pull 
> request to fix this. 
>  
>

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Re: Should reverse() return a Unicode string?

[Carl Meyer]

Hi Jon,

On 09/18/2014 02:01 PM, Jon Dufresne wrote:
> In my Django application, I'm making a strong attempt to always deal
> with Unicode strings at the application layer. Byte strings are only
> handled at the protocol layer -- sending data out on the "wire". If my
> application tests if an object is a string, I'll use isinstance(obj,
> unicode) (Python2).
> 
> One gotcha that I noticed is that reverse() will always return a byte
> string. Tracing this through the code, I see this happens during the
> call to iri_to_uri(), as this function creates a string consisting
> only of ASCII characters, other characters are escaped.
> 
> Now, reverse() is often used to grab a URL and handle it at the
> application layer. It is not reserved only for the protocol layer. An
> example would be presenting a URL inside a HTML template, (as an href
> or as text), mail, or JSON.
> 
> In my opinion, reverse() should return a Unicode string, even if that
> string consists only of ASCII characters. It is not until the string
> hits the wire that it ought to be forced to bytes.
> 
> To verify this, I have created a unit test that I placed in
> "urlpatterns_reverse.tests.URLPatternReverse" to demonstrate this is
> at the Django layer.
> 
> def test_reverse_unicode(self):
> name, expected, args, kwargs = test_data[0]
> self.assertIsInstance(
> reverse(name, args=args, kwargs=kwargs),
> six.text_type)
> 
> What do you think? If others agree, I can file a bug and create a pull
> request to fix this.

It makes sense to me that `reverse()` should return a text (unicode)
string. A URL may be "just bytes" on the network, but within the Django
context it is clearly text.

I'm a bit concerned about the backwards-compatibility implications,
particularly for Python 3 projects where `bytes` and `str` don't
silently interoperate. It would be really interesting to hear if anyone
on this list has a real-world Python 3 Django project handy and could
test the impact of this change.

Carl

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Should reverse() return a Unicode string?

[Jon Dufresne]

Hi,

In my Django application, I'm making a strong attempt to always deal
with Unicode strings at the application layer. Byte strings are only
handled at the protocol layer -- sending data out on the "wire". If my
application tests if an object is a string, I'll use isinstance(obj,
unicode) (Python2).

One gotcha that I noticed is that reverse() will always return a byte
string. Tracing this through the code, I see this happens during the
call to iri_to_uri(), as this function creates a string consisting
only of ASCII characters, other characters are escaped.

Now, reverse() is often used to grab a URL and handle it at the
application layer. It is not reserved only for the protocol layer. An
example would be presenting a URL inside a HTML template, (as an href
or as text), mail, or JSON.

In my opinion, reverse() should return a Unicode string, even if that
string consists only of ASCII characters. It is not until the string
hits the wire that it ought to be forced to bytes.

To verify this, I have created a unit test that I placed in
"urlpatterns_reverse.tests.URLPatternReverse" to demonstrate this is
at the Django layer.

def test_reverse_unicode(self):
name, expected, args, kwargs = test_data[0]
self.assertIsInstance(
reverse(name, args=args, kwargs=kwargs),
six.text_type)

What do you think? If others agree, I can file a bug and create a pull
request to fix this.

Thanks,
Jon

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