stages/prompt: fix username field throwing error with existing user (#9342)

Signed-off-by: Jens Langhammer <jens@goauthentik.io>

authentik/stages/prompt/stage.py

@@ -150,22 +150,26 @@ class PromptChallengeResponse(ChallengeResponse):
         return attrs
 
 
-def username_field_validator_factory() -> Callable[[PromptChallenge, str], Any]:
+def username_field_validator_factory() -> Callable[[PromptChallengeResponse, str], Any]:
     """Return a `clean_` method for `field`. Clean method checks if username is taken already."""
 
-    def username_field_validator(_: PromptChallenge, value: str) -> Any:
+    def username_field_validator(self: PromptChallengeResponse, value: str) -> Any:
         """Check for duplicate usernames"""
-        if User.objects.filter(username=value).exists():
+        pending_user = self.stage.get_pending_user()
+        query = User.objects.all()
+        if pending_user.pk:
+            query = query.exclude(username=pending_user.username)
+        if query.filter(username=value).exists():
             raise ValidationError("Username is already taken.")
         return value
 
     return username_field_validator
 
 
-def password_single_validator_factory() -> Callable[[PromptChallenge, str], Any]:
+def password_single_validator_factory() -> Callable[[PromptChallengeResponse, str], Any]:
     """Return a `clean_` method for `field`. Clean method checks if username is taken already."""
 
-    def password_single_clean(self: PromptChallenge, value: str) -> Any:
+    def password_single_clean(self: PromptChallengeResponse, value: str) -> Any:
         """Send password validation signals for e.g. LDAP Source"""
         password_validate.send(sender=self, password=value, plan_context=self.plan.context)
         return value

blueprints/default/flow-default-source-enrollment.yaml

@@ -16,7 +16,7 @@ entries:
     placeholder: Username
     placeholder_expression: false
     required: true
-    type: text
+    type: username
     field_key: username
     label: Username
   identifiers: