From 4178488881f4e703c4e47ea78720dd61e0230ce5 Mon Sep 17 00:00:00 2001
From: Sergey Fedoseev <fedoseev.sergey@gmail.com>
Date: Wed, 22 Jun 2016 00:57:45 +0500
Subject: [PATCH] Refs #26657 -- Fixed a crash induced by invalid WKT returned
 by MySQL 5.7.5+.

---
 .../gis/db/backends/mysql/operations.py       | 19 ++++++++++++++++++-
 tests/gis_tests/geoapp/test_functions.py      |  2 +-
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/django/contrib/gis/db/backends/mysql/operations.py b/django/contrib/gis/db/backends/mysql/operations.py
index 997ebc9a3c..b59060b221 100644
--- a/django/contrib/gis/db/backends/mysql/operations.py
+++ b/django/contrib/gis/db/backends/mysql/operations.py
@@ -2,7 +2,7 @@ from django.contrib.gis.db.backends.base.adapter import WKTAdapter
 from django.contrib.gis.db.backends.base.operations import \
     BaseSpatialOperations
 from django.contrib.gis.db.backends.utils import SpatialOperator
-from django.contrib.gis.db.models import aggregates
+from django.contrib.gis.db.models import GeometryField, aggregates
 from django.db.backends.mysql.operations import DatabaseOperations
 from django.utils.functional import cached_property
 
@@ -22,6 +22,10 @@ class MySQLOperations(BaseSpatialOperations, DatabaseOperations):
     def is_mysql_5_6(self):
         return self.connection.mysql_version < (5, 7, 6)
 
+    @cached_property
+    def uses_invalid_empty_geometry_collection(self):
+        return self.connection.mysql_version >= (5, 7, 5)
+
     @cached_property
     def select(self):
         if self.is_mysql_5_5:
@@ -105,3 +109,16 @@ class MySQLOperations(BaseSpatialOperations, DatabaseOperations):
         else:
             placeholder = '%s(%%s)' % self.from_text
         return placeholder
+
+    def get_db_converters(self, expression):
+        converters = super(MySQLOperations, self).get_db_converters(expression)
+        if isinstance(expression.output_field, GeometryField) and self.uses_invalid_empty_geometry_collection:
+            converters.append(self.convert_invalid_empty_geometry_collection)
+        return converters
+
+    # https://dev.mysql.com/doc/refman/5.7/en/spatial-function-argument-handling.html
+    # MySQL 5.7.5 adds support for the empty geometry collections, but they are represented with invalid WKT.
+    def convert_invalid_empty_geometry_collection(self, value, expression, connection, context):
+        if value == b'GEOMETRYCOLLECTION()':
+            return b'GEOMETRYCOLLECTION EMPTY'
+        return value
diff --git a/tests/gis_tests/geoapp/test_functions.py b/tests/gis_tests/geoapp/test_functions.py
index 3d42a4e407..c0e0a37ab3 100644
--- a/tests/gis_tests/geoapp/test_functions.py
+++ b/tests/gis_tests/geoapp/test_functions.py
@@ -223,7 +223,7 @@ class GISFunctionsTests(TestCase):
         geom = Point(5, 23, srid=4326)
         qs = Country.objects.annotate(inter=functions.Intersection('mpoly', geom))
         for c in qs:
-            if spatialite or mysql or oracle:
+            if spatialite or (mysql and not connection.ops.uses_invalid_empty_geometry_collection) or oracle:
                 # When the intersection is empty, some databases return None.
                 expected = None
             else: