From 6a1957bb9887f8e0bb69d3d2b180a1414d38c1fc Mon Sep 17 00:00:00 2001
From: Vinay Karanam <vinayinvicible@gmail.com>
Date: Wed, 3 Jan 2018 12:10:14 +0530
Subject: [PATCH] Fixed #28950 -- Fixed ArrayField.has_changed() for empty
 values.

---
 django/contrib/postgres/forms/array.py | 10 ++++++++++
 tests/postgres_tests/test_array.py     |  8 ++++++++
 2 files changed, 18 insertions(+)

diff --git a/django/contrib/postgres/forms/array.py b/django/contrib/postgres/forms/array.py
index f01d5836c1..d9e3256e1f 100644
--- a/django/contrib/postgres/forms/array.py
+++ b/django/contrib/postgres/forms/array.py
@@ -91,6 +91,16 @@ class SimpleArrayField(forms.CharField):
         if errors:
             raise ValidationError(errors)
 
+    def has_changed(self, initial, data):
+        try:
+            value = self.to_python(data)
+        except ValidationError:
+            pass
+        else:
+            if initial in self.empty_values and value in self.empty_values:
+                return False
+        return super().has_changed(initial, data)
+
 
 class SplitArrayWidget(forms.Widget):
     template_name = 'postgres/widgets/split_array.html'
diff --git a/tests/postgres_tests/test_array.py b/tests/postgres_tests/test_array.py
index 71d0603469..cc264fe9fc 100644
--- a/tests/postgres_tests/test_array.py
+++ b/tests/postgres_tests/test_array.py
@@ -760,6 +760,14 @@ class TestSimpleFormField(PostgreSQLTestCase):
         self.assertIs(field.has_changed([1, 2], '1,2,3'), True)
         self.assertIs(field.has_changed([1, 2], 'a,b'), True)
 
+    def test_has_changed_empty(self):
+        field = SimpleArrayField(forms.CharField())
+        self.assertIs(field.has_changed(None, None), False)
+        self.assertIs(field.has_changed(None, ''), False)
+        self.assertIs(field.has_changed(None, []), False)
+        self.assertIs(field.has_changed([], None), False)
+        self.assertIs(field.has_changed([], ''), False)
+
 
 class TestSplitFormField(PostgreSQLTestCase):