Fixed #25583 -- Allowed calling `transform` with `CoordTransform` even if SRID is invalid.

django/contrib/gis/geos/geometry.py

@@ -494,14 +494,18 @@ class GEOSGeometry(GEOSBase, ListMixin):
             else:
                 return
 
-        if (srid is None) or (srid < 0):
+        if isinstance(ct, gdal.CoordTransform):
+            # We don't care about SRID because CoordTransform presupposes
+            # source SRS.
+            srid = None
+        elif srid is None or srid < 0:
             raise GEOSException("Calling transform() with no SRID set is not supported")
 
         if not gdal.HAS_GDAL:
             raise GEOSException("GDAL library is not available to transform() geometry.")
 
         # Creating an OGR Geometry, which is then transformed.
-        g = self.ogr
+        g = gdal.OGRGeometry(self.wkb, srid)
         g.transform(ct)
         # Getting a new GEOS pointer
         ptr = wkb_r().read(g.wkb)

docs/ref/contrib/gis/geos.txt

@@ -553,6 +553,14 @@ is returned instead.
 
     Requires GDAL. Raises :class:`~django.contrib.gis.geos.GEOSException` if
     GDAL is not available or if the geometry's SRID is ``None`` or less than 0.
+    It doesn't impose any constraints on the geometry's SRID if called with a
+    :class:`~django.contrib.gis.gdal.CoordTransform` object.
+
+    .. versionchanged:: 1.10
+
+        In previous versions, it required the geometry's SRID to be a positive
+        integer even if it was called with a
+        :class:`~django.contrib.gis.gdal.CoordTransform` object.
 
 ``Point``
 ---------

tests/gis_tests/geos_tests/test_geos.py

@@ -656,9 +656,10 @@ class GEOSTest(unittest.TestCase, TestDataMixin):
 
     @skipUnless(HAS_GDAL, "GDAL is required.")
     def test_custom_srid(self):
-        """ Test with a srid unknown from GDAL """
-        pnt = Point(111200, 220900, srid=999999)
-        self.assertTrue(pnt.ewkt.startswith("SRID=999999;POINT (111200.0"))
+        """Test with a null srid and a srid unknown to GDAL."""
+        for srid in [None, 999999]:
+            pnt = Point(111200, 220900, srid=srid)
+            self.assertTrue(pnt.ewkt.startswith(("SRID=%s;" % srid if srid else '') + "POINT (111200.0"))
             self.assertIsInstance(pnt.ogr, gdal.OGRGeometry)
             self.assertIsNone(pnt.srs)