modified to_database for handling edits in domain application AO and Submitter

src/registrar/forms/application_wizard.py

@@ -34,6 +34,34 @@ class RegistrarForm(forms.Form):
         self.application = kwargs.pop("application", None)
         super(RegistrarForm, self).__init__(*args, **kwargs)
 
+    def has_more_than_one_join(self, db_obj, rel, related_name):
+        """Helper for finding whether an object is joined more than once."""
+        # threshold is the number of related objects that are acceptable
+        # when determining if related objects exist. threshold is 0 for most
+        # relationships. if the relationship is related_name, we know that
+        # there is already exactly 1 acceptable relationship (the one we are
+        # attempting to delete), so the threshold is 1
+        threshold = 1 if rel == related_name else 0
+
+        # Raise a KeyError if rel is not a defined field on the db_obj model
+        # This will help catch any errors in reverse_join config on forms
+        if rel not in [field.name for field in db_obj._meta.get_fields()]:
+            raise KeyError(f"{rel} is not a defined field on the {db_obj._meta.model_name} model.")
+
+        # if attr rel in db_obj is not None, then test if reference object(s) exist
+        if getattr(db_obj, rel) is not None:
+            field = db_obj._meta.get_field(rel)
+            if isinstance(field, OneToOneField):
+                # if the rel field is a OneToOne field, then we have already
+                # determined that the object exists (is not None)
+                return True
+            elif isinstance(field, ForeignObjectRel):
+                # if the rel field is a ManyToOne or ManyToMany, then we need
+                # to determine if the count of related objects is greater than
+                # the threshold
+                return getattr(db_obj, rel).count() > threshold
+        return False
+    
     def to_database(self, obj: DomainApplication | Contact):
         """
         Adds this form's cleaned data to `obj` and saves `obj`.
@@ -351,13 +379,27 @@ class AboutYourOrganizationForm(RegistrarForm):
 
 
 class AuthorizingOfficialForm(RegistrarForm):
+    JOIN = "authorizing_official"
+    REVERSE_JOINS = [
+        "user",
+        "authorizing_official",
+        "submitted_applications",
+        "contact_applications",
+        "information_authorizing_official",
+        "submitted_applications_information",
+        "contact_applications_information",
+    ]
+    
     def to_database(self, obj):
         if not self.is_valid():
             return
         contact = getattr(obj, "authorizing_official", None)
-        if contact is not None:
+        if contact is not None and not any(self.has_more_than_one_join(contact, rel, "authorizing_official") for rel in self.REVERSE_JOINS):
+            # if contact exists in the database and is not joined to other entities
             super().to_database(contact)
         else:
+            # no contact exists OR contact exists which is joined also to other entities;
+            # in either case, create a new contact and update it
             contact = Contact()
             super().to_database(contact)
             obj.authorizing_official = contact
@@ -549,13 +591,27 @@ class PurposeForm(RegistrarForm):
 
 
 class YourContactForm(RegistrarForm):
+    JOIN = "submitter"
+    REVERSE_JOINS = [
+        "user",
+        "authorizing_official",
+        "submitted_applications",
+        "contact_applications",
+        "information_authorizing_official",
+        "submitted_applications_information",
+        "contact_applications_information",
+    ]
+
     def to_database(self, obj):
         if not self.is_valid():
             return
         contact = getattr(obj, "submitter", None)
-        if contact is not None:
+        if contact is not None and not any(self.has_more_than_one_join(contact, rel, "submitted_applications") for rel in self.REVERSE_JOINS):
+            # if contact exists in the database and is not joined to other entities
             super().to_database(contact)
         else:
+            # no contact exists OR contact exists which is joined also to other entities;
+            # in either case, create a new contact and update it
             contact = Contact()
             super().to_database(contact)
             obj.submitter = contact