Add test cases for creating a user with username already existing

oidc/viewsets.py

@@ -245,27 +245,21 @@ def _clean_user_data(self, user_data) -> Tuple[dict, Optional[list]]:
             ) and "email" in user_data:
                 username = user_data["email"].split("@")[0]
                 if (
-                    self.user_model.objects.filter(username__iexact=username).count()
-                    == 0
+                    self.replaceable_username_characters
+                    and self.username_char_replacement
                 ):
-                    username = user_data["email"].split("@")[0]
-                    if (
-                        self.replaceable_username_characters
-                        and self.username_char_replacement
-                    ):
-                        for char in list(self.replaceable_username_characters):
-                            username = username.replace(
-                                char, self.username_char_replacement
-                            )
+                    for char in list(self.replaceable_username_characters):
+                        username = username.replace(
+                            char, self.username_char_replacement
+                        )
 
-                    # Validate retrieved username matches regex
-                    if (
-                        "username" in self.field_validation_regex
-                        and username_regex.search(username)
-                    ):
-                        user_data["username"] = username
-                        if "username" in missing_fields:
-                            missing_fields.remove("username")
+                # Validate retrieved username matches regex
+                if "username" in self.field_validation_regex and username_regex.search(
+                    username
+                ):
+                    user_data["username"] = username
+                    if "username" in missing_fields:
+                        missing_fields.remove("username")
 
         return user_data, missing_fields
 
@@ -277,6 +271,7 @@ def callback(self, request: HttpRequest, **kwargs: dict) -> HttpResponse:  # noq
         if client:
             user_data = request.POST.dict()
             id_token = user_data.get("id_token")
+            provided_username = user_data.get("username")
 
             if not id_token and user_data.get("code"):
                 try:
@@ -304,6 +299,8 @@ def callback(self, request: HttpRequest, **kwargs: dict) -> HttpResponse:  # noq
                         redirect_after = decoded_token.pop(REDIRECT_AFTER_AUTH)
                     user_data.update(decoded_token)
                     user_data = self.map_claims_to_model_field(user_data)
+                    if provided_username:
+                        user_data.update({"username": provided_username})
                     filter_kwargs = None
 
                     if "email" in user_data:

tests/test_viewsets.py

@@ -35,6 +35,7 @@
     "MAP_CLAIM_TO_MODEL": {
         "given_name": "first_name",
         "family_name": "last_name",
+        "preferred_username": "username",
         "sub": "email",
     },
     "USER_DEFAULTS": {
@@ -87,6 +88,85 @@ def test_returns_data_entry_template_on_missing_username_claim(self):
             self.assertEqual(response.status_code, 200)
             self.assertEqual(response.template_name, "oidc/oidc_user_data_entry.html")
 
+    @override_settings(OPENID_CONNECT_VIEWSET_CONFIG=OPENID_CONNECT_VIEWSET_CONFIG)
+    def test_create_user_providing_id_token_in_form(self):
+        """
+        Trying to create a user that already exists will ask you to chose a different username
+        """
+        view = UserModelOpenIDConnectViewset.as_view({"post": "callback"})
+        with patch(
+            "oidc.viewsets.OpenIDClient.verify_and_decode_id_token"
+        ) as mock_func:
+            mock_func.return_value = {
+                "email_verified": False,
+                "name": "Alice User",
+                "preferred_username": "[email protected]",
+                "given_name": "user",
+                "family_name": "Alice",
+                "email": "[email protected]",
+            }
+
+            data = {
+                "id_token": "sadsdaio3209lkasdlkas0d.sdojdsiad.iosdadia",
+            }
+            request = self.factory.post("/", data=data)
+            response = view(request, auth_server="default")
+            self.assertEqual(response.status_code, 302)
+            user = User.objects.get(username="useralice")
+            self.assertEqual(user.email, "[email protected]")
+
+        # when email username is already in use erorr message should reflect that
+        with patch(
+            "oidc.viewsets.OpenIDClient.verify_and_decode_id_token"
+        ) as mock_func:
+            mock_func.return_value = {
+                "email_verified": False,
+                "name": "Alice User",
+                "preferred_username": "[email protected]",
+                "given_name": "user",
+                "family_name": "Alice",
+                "email": "[email protected]",
+            }
+
+            data = {
+                "id_token": "sadsdaio3209lkasdlkas0d.sdojdsiad.iosdadia",
+            }
+            request = self.factory.post("/", data=data)
+            response = view(request, auth_server="default")
+
+            self.assertEqual(user.email, "[email protected]")
+            self.assertEqual(response.template_name, "oidc/oidc_user_data_entry.html")
+            self.assertEqual(response.status_code, 200)
+            self.assertEqual(
+                response.data["error"],
+                "Username field is already in use.",
+            )
+
+        # when preferred username is provided, use the preferred username
+        with patch(
+            "oidc.viewsets.OpenIDClient.verify_and_decode_id_token"
+        ) as mock_func:
+            mock_func.return_value = {
+                "email_verified": False,
+                "name": "Alice User",
+                "preferred_username": "[email protected]",
+                "given_name": "user",
+                "family_name": "Alice",
+                "email": "[email protected]",
+            }
+
+            data = {
+                "id_token": "sadsdaio3209lkasdlkas0d.sdojdsiad.iosdadia",
+                "username": "preferredusername",
+            }
+            request = self.factory.post("/", data=data)
+            response = view(request, auth_server="default")
+
+            self.assertEqual(user.email, "[email protected]")
+            self.assertEqual(response.status_code, 302)
+            user = User.objects.get(username="preferredusername")
+            self.assertEqual(user.email, "[email protected]")
+
     @override_settings(OPENID_CONNECT_VIEWSET_CONFIG=OPENID_CONNECT_VIEWSET_CONFIG)
     def test_recreating_already_existing_user(self):
         """