Fixed #36363 -- Added field names to admin duplicated fields error hint.

django/contrib/admin/checks.py

@@ -331,11 +331,15 @@ class BaseModelAdminChecks:
                     id="admin.E005",
                 )
             ]
-        fields = flatten(obj.fields)
+        field_counts = collections.Counter(flatten(obj.fields))
-        if len(fields) != len(set(fields)):
+        if duplicate_fields := [
+            field for field, count in field_counts.items() if count > 1
+        ]:
             return [
                 checks.Error(
                     "The value of 'fields' contains duplicate field(s).",
+                    hint="Remove duplicates of %s."
+                    % ", ".join(map(repr, duplicate_fields)),
                     obj=obj.__class__,
                     id="admin.E006",
                 )
@@ -397,11 +401,20 @@ class BaseModelAdminChecks:
                 id="admin.E008",
             )
 
-        seen_fields.extend(flatten(fieldset[1]["fields"]))
+        fieldset_fields = flatten(fieldset[1]["fields"])
-        if len(seen_fields) != len(set(seen_fields)):
+        seen_fields.extend(fieldset_fields)
+        field_counts = collections.Counter(seen_fields)
+        fieldset_fields_set = set(fieldset_fields)
+        if duplicate_fields := [
+            field
+            for field, count in field_counts.items()
+            if count > 1 and field in fieldset_fields_set
+        ]:
             return [
                 checks.Error(
                     "There are duplicate field(s) in '%s[1]'." % label,
+                    hint="Remove duplicates of %s."
+                    % ", ".join(map(repr, duplicate_fields)),
                     obj=obj.__class__,
                     id="admin.E012",
                 )
@@ -469,10 +482,15 @@ class BaseModelAdminChecks:
             return must_be(
                 "a list or tuple", option="exclude", obj=obj, id="admin.E014"
             )
-        elif len(obj.exclude) > len(set(obj.exclude)):
+        field_counts = collections.Counter(obj.exclude)
+        if duplicate_fields := [
+            field for field, count in field_counts.items() if count > 1
+        ]:
             return [
                 checks.Error(
                     "The value of 'exclude' contains duplicate field(s).",
+                    hint="Remove duplicates of %s."
+                    % ", ".join(map(repr, duplicate_fields)),
                     obj=obj.__class__,
                     id="admin.E015",
                 )

tests/admin_checks/tests.py

@@ -479,6 +479,7 @@ class SystemChecksTestCase(SimpleTestCase):
         expected = [
             checks.Error(
                 "The value of 'exclude' contains duplicate field(s).",
+                hint="Remove duplicates of 'name'.",
                 obj=ExcludedFields2,
                 id="admin.E015",
             )
@@ -970,6 +971,7 @@ class SystemChecksTestCase(SimpleTestCase):
         expected = [
             checks.Error(
                 "The value of 'fields' contains duplicate field(s).",
+                hint="Remove duplicates of 'state'.",
                 obj=MyModelAdmin,
                 id="admin.E006",
             )
@@ -986,12 +988,38 @@ class SystemChecksTestCase(SimpleTestCase):
         expected = [
             checks.Error(
                 "There are duplicate field(s) in 'fieldsets[0][1]'.",
+                hint="Remove duplicates of 'title', 'album'.",
                 obj=MyModelAdmin,
                 id="admin.E012",
             )
         ]
         self.assertEqual(errors, expected)
 
+    def test_check_multiple_duplicates_across_fieldsets(self):
+        class MyModelAdmin(admin.ModelAdmin):
+            fieldsets = [
+                ("Header 1", {"fields": ["title", "album"]}),
+                ("Header 2", {"fields": ["album", "name"]}),
+                ("Header 3", {"fields": ["name", "other", "title"]}),
+            ]
+
+        errors = MyModelAdmin(Song, AdminSite()).check()
+        expected = [
+            checks.Error(
+                "There are duplicate field(s) in 'fieldsets[1][1]'.",
+                hint="Remove duplicates of 'album'.",
+                obj=MyModelAdmin,
+                id="admin.E012",
+            ),
+            checks.Error(
+                "There are duplicate field(s) in 'fieldsets[2][1]'.",
+                hint="Remove duplicates of 'title', 'name'.",
+                obj=MyModelAdmin,
+                id="admin.E012",
+            ),
+        ]
+        self.assertEqual(errors, expected)
+
     def test_list_filter_works_on_through_field_even_when_apps_not_ready(self):
         """
         Ensure list_filter can access reverse fields even when the app registry

tests/modeladmin/test_checks.py

@@ -222,6 +222,7 @@ class FieldsetsCheckTests(CheckTestCase):
             ValidationTestModel,
             "There are duplicate field(s) in 'fieldsets[0][1]'.",
             "admin.E012",
+            "Remove duplicates of 'name'.",
         )
 
     def test_duplicate_fields_in_fieldsets(self):
@@ -236,6 +237,7 @@ class FieldsetsCheckTests(CheckTestCase):
             ValidationTestModel,
             "There are duplicate field(s) in 'fieldsets[1][1]'.",
             "admin.E012",
+            "Remove duplicates of 'name'.",
         )
 
     def test_fieldsets_with_custom_form_validation(self):
@@ -255,6 +257,7 @@ class FieldsCheckTests(CheckTestCase):
             ValidationTestModel,
             "The value of 'fields' contains duplicate field(s).",
             "admin.E006",
+            "Remove duplicates of 'name'.",
         )
 
     def test_inline(self):