raise ImproperlyConfigured if basename already exists

rest_framework/routers.py

@@ -52,12 +52,27 @@ class BaseRouter:
     def register(self, prefix, viewset, basename=None):
         if basename is None:
             basename = self.get_default_basename(viewset)
-        self.registry.append((prefix, viewset, basename))
+
+        if not self.basename_already_registered(basename):
+            self.registry.append((prefix, viewset, basename))
 
         # invalidate the urls cache
         if hasattr(self, '_urls'):
             del self._urls
 
+    def basename_already_registered(self, new_basename):
+        """
+        If `basename` is already registered, raise an exception
+        """
+        for route in self.registry:
+            prefix, viewset, basename = route
+            if new_basename == basename:
+                msg = (f'Route with basename "{new_basename}" is already registered. '
+                       f'Please provide a unique basename for viewset "{viewset}"')
+                raise ImproperlyConfigured(msg)
+
+        return False
+
     def get_default_basename(self, viewset):
         """
         If `basename` is not specified, attempt to automatically determine

tests/test_routers.py

@@ -481,3 +481,17 @@ class TestViewInitkwargs(URLPatternsTestCase, TestCase):
         initkwargs = match.func.initkwargs
 
         assert initkwargs['basename'] == 'routertestmodel'
+
+
+class TestDuplicateBasename(URLPatternsTestCase, TestCase):
+    def test_exception_for_duplicate_basename(self):
+        class NoteViewSet(viewsets.ModelViewSet):
+            queryset = RouterTestModel.objects.all()
+
+        self.router = SimpleRouter(trailing_slash=False)
+        self.router.register(r'notes', NoteViewSet)
+
+        with pytest.raises(ImproperlyConfigured):
+            self.router.register(r'notes_duplicate', NoteViewSet)
+
+        self.router.register(r'notes_duplicate_2', NoteViewSet, basename='note_duplicate')