[1.9.x] Fixed #26557 -- Converted empty strings to None when saving GenericIPAddressField.

Backport of 4681d65048ca2553895e10c2c492997b0a78ffba from master

3 files changed, 12 insertions, 1 deletions

diff --git a/django/db/backends/base/operations.py b/django/db/backends/base/operations.py
index acca12708a..5d3cddff9d 100644
--- a/django/db/backends/base/operations.py
+++ b/django/db/backends/base/operations.py
@@ -497,7 +497,7 @@ class BaseDatabaseOperations(object):
         Transforms a string representation of an IP address into the expected
         type for the backend driver.
         """
-        return value
+        return value or None
 
     def year_lookup_bounds_for_date_field(self, value):
         """
diff --git a/docs/releases/1.9.6.txt b/docs/releases/1.9.6.txt
index 7e3f6aed6a..769d04945a 100644
--- a/docs/releases/1.9.6.txt
+++ b/docs/releases/1.9.6.txt
@@ -24,3 +24,6 @@ Bugfixes
 
 * Fixed a regression causing the cached template loader to crash when using
   template names starting with a dash (:ticket:`26536`).
+
+* Restored conversion of an empty string to null when saving values of
+  ``GenericIPAddressField`` on SQLite and MySQL (:ticket:`26557`).
diff --git a/tests/model_fields/tests.py b/tests/model_fields/tests.py
index cc6639b032..b103baeedb 100644
--- a/tests/model_fields/tests.py
+++ b/tests/model_fields/tests.py
@@ -900,6 +900,14 @@ class GenericIPAddressFieldTests(test.TestCase):
         o = GenericIPAddress.objects.get()
         self.assertIsNone(o.ip)
 
+    def test_blank_string_saved_as_null(self):
+        o = GenericIPAddress.objects.create(ip='')
+        o.refresh_from_db()
+        self.assertIsNone(o.ip)
+        GenericIPAddress.objects.update(ip='')
+        o.refresh_from_db()
+        self.assertIsNone(o.ip)
+
     def test_save_load(self):
         instance = GenericIPAddress.objects.create(ip='::1')
         loaded = GenericIPAddress.objects.get()