From 4fbe3ecce654614232f94362d51184e241ac07c6 Mon Sep 17 00:00:00 2001
From: Ryan P Kilby <rpkilby@ncsu.edu>
Date: Sat, 18 Nov 2017 13:54:48 -0500
Subject: [PATCH] Add request.current_app handling to drf reverse

---
 rest_framework/reverse.py |  17 +++++++
 tests/test_reverse.py     | 100 ++++++++++++++++++++++++++++++++++++--
 2 files changed, 112 insertions(+), 5 deletions(-)

diff --git a/rest_framework/reverse.py b/rest_framework/reverse.py
index 54c463553..d5123d351 100644
--- a/rest_framework/reverse.py
+++ b/rest_framework/reverse.py
@@ -60,10 +60,27 @@ def _reverse(viewname, args=None, kwargs=None, request=None, format=None, **extr
     if format is not None:
         kwargs = kwargs or {}
         kwargs['format'] = format
+    if request:
+        extra.setdefault('current_app', current_app(request))
     url = django_reverse(viewname, args=args, kwargs=kwargs, **extra)
     if request:
         return request.build_absolute_uri(url)
     return url
 
 
+def current_app(request):
+    """
+    Get the current app for the request.
+
+    This code is copied from the URL tag.
+    """
+    try:
+        return request.current_app
+    except AttributeError:
+        try:
+            return request.resolver_match.namespace
+        except AttributeError:
+            return None
+
+
 reverse_lazy = lazy(reverse, six.text_type)
diff --git a/tests/test_reverse.py b/tests/test_reverse.py
index 145b1a54f..473a82ffd 100644
--- a/tests/test_reverse.py
+++ b/tests/test_reverse.py
@@ -1,21 +1,29 @@
 from __future__ import unicode_literals
 
-from django.conf.urls import url
+from django.conf.urls import include, url
+from django.http import HttpResponse
 from django.test import TestCase, override_settings
 from django.urls import NoReverseMatch
 
-from rest_framework.reverse import reverse
+from rest_framework.reverse import current_app, reverse
 from rest_framework.test import APIRequestFactory
 
 factory = APIRequestFactory()
 
 
-def null_view(request):
-    pass
+def mock_view(request):
+    return HttpResponse('')
+
+
+apppatterns = ([
+    url(r'^home$', mock_view, name='home'),
+], 'app')
 
 
 urlpatterns = [
-    url(r'^view$', null_view, name='view'),
+    url(r'^view$', mock_view, name='view'),
+    url(r'^app2/', include(apppatterns, namespace='app2')),
+    url(r'^app1/', include(apppatterns, namespace='app1')),
 ]
 
 
@@ -54,3 +62,85 @@ class ReverseTests(TestCase):
 
         url = reverse('view', request=request)
         assert url == 'http://testserver/view'
+
+
+@override_settings(ROOT_URLCONF='tests.test_reverse')
+class NamespaceTests(TestCase):
+    """
+    Ensure reverse can handle namespaces.
+
+    Note: It's necessary to use self.client() here, as the
+          RequestFactory does not setup the resolver_match.
+    """
+
+    def request(self, url):
+        return self.client.get(url).wsgi_request
+
+    def test_application_namespace(self):
+        url = reverse('app:home')
+        assert url == '/app1/home'
+
+        # instance namespace provided by current_app
+        url = reverse('app:home', current_app='app2')
+        assert url == '/app2/home'
+
+    def test_instance_namespace(self):
+        url = reverse('app1:home')
+        assert url == '/app1/home'
+
+        url = reverse('app2:home')
+        assert url == '/app2/home'
+
+    def test_application_namespace_with_request(self):
+        # request's current app affects result
+        request1 = self.request('/app1/home')
+        request2 = self.request('/app2/home')
+
+        # sanity check
+        assert current_app(request1) == 'app1'
+        assert current_app(request2) == 'app2'
+
+        assert reverse('app:home', request=request1) == 'http://testserver/app1/home'
+        assert reverse('app:home', request=request2) == 'http://testserver/app2/home'
+
+    def test_instance_namespace_with_request(self):
+        # request's current app is not relevant
+        request1 = self.request('/app1/home')
+        request2 = self.request('/app2/home')
+
+        # sanity check
+        assert current_app(request1) == 'app1'
+        assert current_app(request2) == 'app2'
+
+        assert reverse('app1:home', request=request1) == 'http://testserver/app1/home'
+        assert reverse('app2:home', request=request1) == 'http://testserver/app2/home'
+        assert reverse('app1:home', request=request2) == 'http://testserver/app1/home'
+        assert reverse('app2:home', request=request2) == 'http://testserver/app2/home'
+
+
+@override_settings(ROOT_URLCONF='tests.test_reverse')
+class CurrentAppTests(TestCase):
+    """
+    Test current_app() function.
+
+    Note: It's necessary to use self.client() here, as the
+          RequestFactory does not setup the resolver_match.
+    """
+
+    def request(self, url):
+        return self.client.get(url).wsgi_request
+
+    def test_no_namespace(self):
+        request = self.request('/view')
+        assert current_app(request) == ''
+
+    def test_namespace(self):
+        request = self.request('/app1/home')
+        assert current_app(request) == 'app1'
+
+        request = self.request('/app2/home')
+        assert current_app(request) == 'app2'
+
+    def test_factory_incompatibility(self):
+        request = factory.get('/app1/home')
+        assert current_app(request) is None