Fixed #23757 -- Added 3D introspection support to Spatialite backend

Thanks Tim Graham for the review.

django/contrib/gis/db/backends/base/features.py

@@ -14,6 +14,8 @@ class BaseSpatialFeatures(object):
     # Does the backend introspect GeometryField to its subtypes?
     supports_geometry_field_introspection = True
 
+    # Does the backend support storing 3D geometries?
+    supports_3d_storage = False
     # Reference implementation of 3D functions is:
     # http://postgis.net/docs/PostGIS_Special_Functions_Index.html#PostGIS_3D_Functions
     supports_3d_functions = False

django/contrib/gis/db/backends/postgis/features.py

@@ -4,5 +4,6 @@ from django.db.backends.postgresql_psycopg2.features import \
 
 
 class DatabaseFeatures(BaseSpatialFeatures, Psycopg2DatabaseFeatures):
+    supports_3d_storage = True
     supports_3d_functions = True
     supports_left_right_lookups = True

django/contrib/gis/db/backends/spatialite/features.py

@@ -1,4 +1,5 @@
 from django.contrib.gis.db.backends.base.features import BaseSpatialFeatures
+from django.contrib.gis.geos import geos_version
 from django.db.backends.sqlite3.features import \
     DatabaseFeatures as SQLiteDatabaseFeatures
 from django.utils.functional import cached_property
@@ -15,3 +16,7 @@ class DatabaseFeatures(BaseSpatialFeatures, SQLiteDatabaseFeatures):
         # which can result in a significant performance improvement when
         # creating the database.
         return self.connection.ops.spatial_version >= (4, 1, 0)
+
+    @cached_property
+    def supports_3d_storage(self):
+        return geos_version() >= '3.3'

django/contrib/gis/db/backends/spatialite/introspection.py

@@ -41,7 +41,13 @@ class SpatiaLiteIntrospection(DatabaseIntrospection):
 
             # OGRGeomType does not require GDAL and makes it easy to convert
             # from OGC geom type name to Django field.
-            field_type = OGRGeomType(row[2]).django
+            ogr_type = row[2]
+            if isinstance(ogr_type, six.integer_types) and ogr_type > 1000:
+                # Spatialite versions >= 4 use the new SFSQL 1.2 offsets
+                # 1000 (Z), 2000 (M), and 3000 (ZM) to indicate the presence of
+                # higher dimensional coordinates (M not yet supported by Django).
+                ogr_type = ogr_type % 1000 + OGRGeomType.wkb25bit
+            field_type = OGRGeomType(ogr_type).django
 
             # Getting any GeometryField keyword arguments that are not the default.
             dim = row[0]
@@ -49,7 +55,7 @@ class SpatiaLiteIntrospection(DatabaseIntrospection):
             field_params = {}
             if srid != 4326:
                 field_params['srid'] = srid
-            if isinstance(dim, six.string_types) and 'Z' in dim:
+            if (isinstance(dim, six.string_types) and 'Z' in dim) or dim == 3:
                 field_params['dim'] = 3
         finally:
             cursor.close()