fix(chant create): move folio-sequence uniqueness check to Form obj

Moves validity checks on the Chant Create view to the Chant Create Form.

Refs: #1713.

django/cantusdb_project/main_app/forms.py

@@ -170,6 +170,7 @@ class Meta:
             "incipit_of_refrain",
             "later_addition",
             "rubrics",
+            "source",
         ]
         # the widgets dictionary is ignored for a model field with a non-empty
         # choices attribute. In this case, you must override the form field to
@@ -239,17 +240,23 @@ class Meta:
         help_text="Select the project (if any) that the chant belongs to.",
     )
 
-    # automatically computed fields
-    # source and incipit are mandatory fields in model,
-    # but have to be optional in the form, otherwise the field validation won't pass
-    source = forms.ModelChoiceField(
-        queryset=Source.objects.all().order_by("title"),
-        required=False,
-        error_messages={
-            "invalid_choice": "This source does not exist, please switch to a different source."
-        },
-    )
-    incipit = forms.CharField(required=False)
+    def clean(self) -> dict[str, Any]:
+        """
+        Provide custom clean method that ensures the created chant does
+        not duplicate the folio and c_sequence of an already-existing chant.
+        """
+        # Call super().clean() to ensure that the form's built-in validation
+        # is run before our custom validation.
+        super().clean()
+        folio = self.cleaned_data["folio"]
+        c_sequence = self.cleaned_data["c_sequence"]
+        source = self.cleaned_data["source"]
+        if source.chant_set.filter(folio=folio, c_sequence=c_sequence):
+            raise forms.ValidationError(
+                "Chant with the same sequence and folio already exists in this source.",
+                code="duplicate-folio-sequence",
+            )
+        return self.cleaned_data
 
 
 class SourceCreateForm(forms.ModelForm):

django/cantusdb_project/main_app/views/chant.py

@@ -880,8 +880,16 @@ def test_func(self):
 
         return user_can_edit_chants_in_source(user, self.source)
 
-    # if success_url and get_success_url not specified, will direct to chant detail page
     def get_success_url(self):
+        """
+        Get the incipit of the created chant (generated by a signal)
+        and display a success message.
+        """
+        self.object.refresh_from_db()
+        messages.success(
+            self.request,
+            "Chant '" + self.object.incipit + "' created successfully!",
+        )
         return reverse("chant-create", args=[self.source.id])
 
     def get_initial(self):
@@ -960,53 +968,24 @@ def get_context_data(self, **kwargs: Any) -> dict[Any, Any]:
         context["suggested_chants"] = suggested_chants
         return context
 
-    def form_valid(self, form):
+    def get_form_kwargs(self):
         """
-        Validates the new chant.
-
-        Custom validation steps are:
-        - Check if a chant with the same sequence and folio already exists in the source.
-        - Compute the chant incipit.
-        - Adds the "created_by" and "updated_by" fields to the chant.
+        In the case of a submitted form (there is data in the request),
+        we copy the data dictionary and add the source id to it.
         """
-        # compute source
-        form.instance.source = self.source
-
-        # compute incipit, within 30 charactors, keep words complete
-        words = form.instance.manuscript_full_text_std_spelling.split(" ")
-        incipit = ""
-        for word in words:
-            new_incipit = incipit + word + " "
-            if len(new_incipit) >= 30:
-                break
-            incipit = new_incipit
-
-        form.instance.incipit = incipit.strip(" ")
-
-        # if a chant with the same sequence and folio already exists in the source
-        if (
-            Chant.objects.all()
-            .filter(
-                source=self.source,
-                folio=form.instance.folio,
-                c_sequence=form.instance.c_sequence,
-            )
-            .exists()
-        ):
-            form.add_error(
-                None,
-                "Chant with the same sequence and folio already exists in this source.",
-            )
+        kwargs = super().get_form_kwargs()
+        if "data" in kwargs:
+            kwargs["data"] = kwargs["data"].copy()
+            kwargs["data"]["source"] = self.source.id
+        return kwargs
 
-        if form.is_valid():
-            form.instance.created_by = self.request.user
-            form.instance.last_updated_by = self.request.user
-            messages.success(
-                self.request,
-                "Chant '" + form.instance.incipit + "' created successfully!",
-            )
-            return super().form_valid(form)
-        return super().form_invalid(form)
+    def form_valid(self, form):
+        """
+        Adds the "created_by" and "updated_by" fields to the chant.
+        """
+        form.instance.created_by = self.request.user
+        form.instance.last_updated_by = self.request.user
+        return super().form_valid(form)
 
 
 class ChantDeleteView(LoginRequiredMixin, UserPassesTestMixin, DeleteView):