Thanks for taking the time to write up this proposal. I agree on pretty
much all counts, but I do have a few comments:
1)
If an app has templates and view code that are reversing
<app_name>:<view_name>, then changing the app name (e.g. by an undocumented
feature, passing a (patterns, app_name) tuple), then all those URLs will
break. Unless I'm missing something, an app *must always* be installed with
the app name that is hard coded in its templates and view code, so there is
no workaround for app namespace conflicts?
Does or would it work to allow two apps with the same app namespace, as
long as they both are installed with customised instance names, so that the
"default app" namespace lookup doesn't return anything, and Django must
fallback to the `current_app` to determine which app is being reversed?
2)
I'd rather see the "app name, period" (as opposed to a default app name)
defined as a variable in an app's URLconf as per #11642 or as an attribute
of the `urlpatterns` object, that Django looks at when a URLconf is
included with a dotted path string, instead of requiring users to import
and then include a `(patterns, app_name)` tuple. Basically, the app name
defined by the app should be used for both of:
include(r^foo/', 'foo.urls')
and
from foo.urls import some_tuple
include(r'^foo/', some_tuple),
3)
Not exactly related to the issue at hand, but if we are reworking URL
namespaces it might be worth some consideration. One reason why I always
avoid using URL namespaces these days is that it becomes impossible to
override an app URL at the project level. Project authors are stuck with
the exact URLs defined by the app author, all located below the same root
path where the URLs are included and with the same view behaviour.
Without namespaced URLs, the project author can include their own version
of a URL at any location (as long as it comes before the app's included
URLs) and change the view behaviour. For namespaced URLs, I'd like to be
able to do something like:
urlpatterns = patterns('',
url(r'^my_foo_login/$', 'myapp.views.my_foo_login', name='login',
app='foo', namespace='foo'),
url(r'^foo/', include('foo.urls', app='foo', namespace='foo')),
)
Then when templates or view code in the `foo` app does reverse('foo:login')
they will get `/my_foo_login/` instead of `/foo/login/` and I can change
the behaviour of the view.
Cheers.
Tai.
On Friday, May 29, 2015 at 1:21:58 AM UTC+10, Marten Kenbeek wrote:
>
> Sure, I'll go through the list of url tickets on Trac.
>
> The key difference with #11642 is "default". What I propose is that
> urls.py specifies the app_name, period. The only reason to change app_name
> is conflicting app names, and there are easy workarounds that I feel
> shouldn't be part of the API itself. The namespace would be specified in
> include(), and default to the app_name.
>
> Op donderdag 28 mei 2015 15:37:20 UTC+2 schreef Tim Graham:
>>
>> Point 1 sounds like https://code.djangoproject.com/ticket/11642 -- and
>> that ticket says it may be superseded by
>> https://code.djangoproject.com/ticket/21927. Could you review those
>> tickets as well as the others in the "Core (URLs)" component of Trac? It
>> would be good if you could assign yourself any tickets that your project
>> will address.
>>
>> On Wednesday, May 27, 2015 at 5:58:00 PM UTC-4, Marten Kenbeek wrote:
>>>
>>> Hi all,
>>>
>>> URL namespaces have a few quirks that make them a bit difficult to use
>>> and understand. I hope to create a patch that clears up these issues.
>>>
>>> First up: the distinction between an application namespace and an
>>> instance namespace. The docs say on the application namespace:
>>>
>>> This describes the name of the application that is being deployed. Every
>>>> instance of a single application will have the same application namespace.
>>>
>>>
>>> And on the instance namespace:
>>>
>>> This identifies a specific instance of an application. Instance
>>>> namespaces should be unique across your entire project. However, an
>>>> instance namespace can be the same as the application namespace. This is
>>>> used to specify a default instance of an application.
>>>
>>>
>>> The current implementation requires that both are specified in the same
>>> place: either in the included url configuration by returning a 3-tuple, or
>>> in the including url configuration through the arguments to include(). The
>>> first case generally does not allow multiple deployments of the same app,
>>> unless the included url configuration contains specific logic to return
>>> different instance namespaces. The second case does not in any way enforce
>>> that multiple deployments in fact have the same application namespace.
>>>
>>> I'd like to get the semantics and the implementation in line, and
>>> provide one obvious way to specify namespaces. Including a set of url
>>> patterns under a namespace involves two parts: the including urlconf that
>>> calls include(), and the included urlconf that is imported by include().
>>> The first is a specific deployment of the imported urlconf; the second is a
>>> single app.
>>>
>>> The obvious way as I see it would be to specify the application
>>> namespace in the app, and specify the instance namespace as a parameter to
>>> include(). This enforces the single application namespace for a single set
>>> of patterns, and allows any end-user to specify the instance namespace on a
>>> per-instance basis. To take the admin as an example:
>>>
>>> admin.site.urls would return a 2-tuple: (patterns, 'admin'), where
>>> 'admin' is the application namespace. (An alternative to a 2-tuple could be
>>> an object with urlpatterns and app_name attributes.)
>>> To include the admin instance, use include(admin.site.urls,
>>> namespace='admin'). This is the instance namespace. If left out, it could
>>> default to be the same as the app name.
>>>
>>> After a deprecation period, it would be an error to specify an instance
>>> namespace if there is no application namespace. This is to ensure that the
>>> app can always reverse its own urls using <app_name>:<view_name> if it
>>> specifies an application namespace, and using <view_name> if it doesn't.
>>> (Setting and app_name would technically still be possible by passing a
>>> hardcoded (patterns, app_name) tuple, just not as an advertised feature.)
>>>
>>> The second point is about nested namespace handling and current_app.
>>>
>>> At the moment, current_app is looking for an exact namespace match.
>>> Unlike the namespaced view path, it is not split into namespace parts using
>>> current_app.split(':'). Take the following (fictional) urlpatterns:
>>>
>>> blog_patterns = [
>>> url(r'^comments-one/', include('comments.urls', 'comments-one',
>>> 'comments')),
>>> url(r'^comments-two/', include('comments.urls', 'comments-two',
>>> 'comments')),
>>> ]
>>>
>>> urlpatterns = [
>>> url(r'^blog-one/', include(blog_patterns, 'blog-one', 'blog')),
>>> url(r'^blog-two/', include(blog_patterns, 'blog-two', 'blog')),
>>> ]
>>>
>>> Because of how current_app is handled, it is now impossible to reverse
>>> patterns in 'blog-one:comments-one:' using current_app. To select
>>> 'blog-one', the current app needs to be the string 'blog-one', but to
>>> select 'comments-one', it needs to be 'comments-one'. The only solution is
>>> to hardcode at least one of the instance namespaces in the namespaced view
>>> path. This also means that setting request.current_app to
>>> request.resolver_match.namespace, as recommended in the docs, does not work
>>> if you have nested namespaces.
>>>
>>> The ResolverMatch object also has some inconsistent behaviour for
>>> app_name. resolver_match.namespace is the full namespace path, i.e.
>>> 'blog-one:comments-one' (with resolver_match.namespaces a list of
>>> individual namespaces, i.e. ['blog-one', 'comments-one']), but
>>> resolver_match.app_name is the outer-most app_name, in this case
>>> 'blog-one', with no trace whatsoever of the full app_name path.
>>>
>>> To illustrate how I would see it end up eventually (after the
>>> deprecation cycle), I've created a branch at
>>> https://github.com/knbk/django/tree/namespaces. I feel these changes
>>> are fairly straightforward, but any comments are appreciated.
>>>
>>> Marten
>>>
>>
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