Make LiveServerTestCase.live_server_url accessible from class

[Moritz Sichert]

Consider following test:

class MySeleniumTest(LiveServerTestCase):
    @classmethod
    def setUpClass(cls):
        super(MySeleniumTest, cls).setUpClass()
        # initialize selenium driver
        cls.selenium = WebDriver()
        # initialize browser state, live_server_url is needed here
        cls.selenium.get(cls.live_server_url)
        # [...]

Right now this doesn't work, because live_server_url is a property even though it only consists of class attributes.

Since class properties are a bit more complicated I suggest adding a get_live_server_url classmethod and keeping the live_server_url.
An alternative is to deprecate live_server_url but I don't think that's really necessary.

[Tim Graham]

Would an approach like this be better than adding a method?

diff --git a/django/test/testcases.py b/django/test/testcases.py
index b17b392..22ab3c1 100644
--- a/django/test/testcases.py
+++ b/django/test/testcases.py
@@ -1245,6 +1245,13 @@ class LiveServerThread(threading.Thread):
             self.httpd.server_close()
 
 
+class classproperty(object):
+    def __init__(self, f):
+        self.f = f
+    def __get__(self, obj, owner):
+        return self.f(owner)
+
+
 class LiveServerTestCase(TransactionTestCase):
     """
     Does basically the same as TransactionTestCase but also launches a live
@@ -1259,7 +1266,7 @@ class LiveServerTestCase(TransactionTestCase):
 
     static_handler = _StaticFilesHandler
 
-    @property
+    @classproperty
     def live_server_url(self):
         return 'http://%s:%s' % (
             self.server_thread.host, self.server_thread.port)

Is it okay for the attribute to fail when not using setUpClass? For example:

>>> from django.test.testcases import LiveServerTestCase
>>> LiveServerTestCase.live_server_url
Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/home/tim/code/django/django/test/testcases.py", line 1252, in __get__
    return self.f(owner)
  File "/home/tim/code/django/django/test/testcases.py", line 1272, in live_server_url
    self.server_thread.host, self.server_thread.port)
AttributeError: type object 'LiveServerTestCase' has no attribute 'server_thread'

[Moritz Sichert]

Yes that would be better and I thought about it, but I didn't want to add a new decorator just for one property.
Should the classproperty go into some utils module then?

I don't see were else it would make sense to use, so I guess that's ok.

[Tim Graham]

django.utils.decorators seems like a good candidate.

[Moritz Sichert]

Updated PR.
Is some additional documentation needed?

[Tim Graham]

I don't think so. A simple test for live_server_url being accessible as a class property might be useful if it's easy.

[Moritz Sichert]

How should I do that?
I could do something like

class TestLiveServerTestCase(LiveServerTestCase):
    @classmethod
    def setUpClass(cls):
        super(TestLiveServerTestCase, cls).setUpClass()
        if isinstance(cls.live_server_url, str):
            cls._test_worked = True
        else:
            cls._test_worked = False

    def test_worked(self):
        self.assertTrue(self._test_worked)

But that feels really hackish.
And instanciating LiveServerTestCase inside a SimpleTestCase isn't that trivial, I think.

[Tim Graham]

Right, I was thinking something like this:

tests/servers/tests.py

@@ -9 +9 @@
 
 from django.core.exceptions import ImproperlyConfigured
 from django.test import LiveServerTestCase, override_settings
+from django.utils import six
 from django.utils._os import upath
 from django.utils.http import urlencode
 from django.utils.six.moves.urllib.error import HTTPError
@@ -71 +72 @@
         else:
             del os.environ['DJANGO_LIVE_TEST_SERVER_ADDRESS']
 
+        cls.live_server_url_type = type(cls.live_server_url)
+
     @classmethod
     def tearDownClass(cls):
         # skip it, as setUpClass doesn't call its parent either
@@ -92 +95 @@
         # test runner and the overridden setUpClass() method is executed.
         pass
 
+    def test_live_server_url_is_class_property(self):
+        self.assertTrue(issubclass(self.live_server_url_type, six.text_type))
+
 
 class LiveServerViews(LiveServerBase):
     def test_404(self):

[Moritz Sichert]

Updated PR, added this test and some documentation.

[Tim Graham <timograham@…>]

In 296919e:

Fixed #24965 -- Made LiveServerTestCase.live_server_url accessible from class

[Tim Graham <timograham@…>]

In d58573e6:

Refs #24965 -- Added changes from accidentally reverted file for last commit.