Add mechanism for deferring required field validation on WagtailAdminModelForm

wagtail/admin/forms/models.py

@@ -103,7 +103,10 @@ def formfield_for_dbfield(db_field, **kwargs):
 class WagtailAdminModelFormOptions(PermissionedFormOptionsMixin, ClusterFormOptions):
     # Container for the options set in the inner 'class Meta' of a model form, supporting
     # extensions for both ClusterForm ('formsets') and PermissionedForm ('field_permissions').
-    pass
+
+    def __init__(self, options=None):
+        super().__init__(options)
+        self.defer_required_on_fields = getattr(options, "defer_required_on_fields", [])
 
 
 class WagtailAdminModelFormMetaclass(PermissionedFormMetaclass, ClusterFormMetaclass):
@@ -125,6 +128,13 @@ class WagtailAdminModelForm(
         self.for_user = kwargs.get("for_user")
         super().__init__(*args, **kwargs)
 
+    def defer_required_fields(self):
+        for field_name in self._meta.defer_required_on_fields:
+            try:
+                self.fields[field_name].required = False
+            except KeyError:
+                pass
+
     class Meta:
         formfield_callback = formfield_for_dbfield
 

wagtail/admin/tests/test_forms.py

@@ -2,6 +2,8 @@ from django.forms.fields import CharField
 from django.test import SimpleTestCase, TestCase
 
 from wagtail.admin.forms.auth import LoginForm, PasswordResetForm
+from wagtail.admin.forms.models import WagtailAdminModelForm
+from wagtail.test.testapp.models import Advert
 
 
 class CustomLoginForm(LoginForm):
@@ -28,3 +30,29 @@ class TestPasswordResetForm(SimpleTestCase):
     def test_extra_fields(self):
         form = CustomPasswordResetForm()
         self.assertEqual(list(form.extra_fields), [("captcha", form["captcha"])])
+
+
+class TestDeferRequiredFields(TestCase):
+    def test_defer_required_fields(self):
+        class AdvertForm(WagtailAdminModelForm):
+            class Meta:
+                model = Advert
+                fields = ["url", "text"]
+                defer_required_on_fields = ["text"]
+
+        form = AdvertForm(
+            {
+                "url": "https://www.example.com",
+                "text": "",
+            }
+        )
+        self.assertFalse(form.is_valid())
+
+        form = AdvertForm(
+            {
+                "url": "https://www.example.com",
+                "text": "",
+            }
+        )
+        form.defer_required_fields()
+        self.assertTrue(form.is_valid())