From c4f20872acc0ebbd3bdbab3a0766d2473661fd93 Mon Sep 17 00:00:00 2001
From: Greg Lucas <greg.m.lucas@gmail.com>
Date: Sat, 29 Jun 2024 07:36:57 -0600
Subject: [PATCH] FIX/MNT: Simplify project geometry handling

The MultiLineString return type was a plain list, but it should be
an empty MultiLineString to be consistent with the other types.
Additionally, all geometry constructors take empty lists, so
just use that rather than special-casing the returns.
---
 lib/cartopy/crs.py                    | 16 +++-------------
 lib/cartopy/tests/test_line_string.py | 10 ++++++++++
 2 files changed, 13 insertions(+), 13 deletions(-)

diff --git a/lib/cartopy/crs.py b/lib/cartopy/crs.py
index c24415167..bc3541987 100644
--- a/lib/cartopy/crs.py
+++ b/lib/cartopy/crs.py
@@ -918,10 +918,7 @@ def _project_multipoint(self, geometry, src_crs):
         geoms = []
         for geom in geometry.geoms:
             geoms.append(self._project_point(geom, src_crs))
-        if geoms:
-            return sgeom.MultiPoint(geoms)
-        else:
-            return sgeom.MultiPoint()
+        return sgeom.MultiPoint(geoms)
 
     def _project_multiline(self, geometry, src_crs):
         geoms = []
@@ -929,10 +926,7 @@ def _project_multiline(self, geometry, src_crs):
             r = self._project_line_string(geom, src_crs)
             if r:
                 geoms.extend(r.geoms)
-        if geoms:
-            return sgeom.MultiLineString(geoms)
-        else:
-            return []
+        return sgeom.MultiLineString(geoms)
 
     def _project_multipolygon(self, geometry, src_crs):
         geoms = []
@@ -940,11 +934,7 @@ def _project_multipolygon(self, geometry, src_crs):
             r = self._project_polygon(geom, src_crs)
             if r:
                 geoms.extend(r.geoms)
-        if geoms:
-            result = sgeom.MultiPolygon(geoms)
-        else:
-            result = sgeom.MultiPolygon()
-        return result
+        return sgeom.MultiPolygon(geoms)
 
     def _project_polygon(self, polygon, src_crs):
         """
diff --git a/lib/cartopy/tests/test_line_string.py b/lib/cartopy/tests/test_line_string.py
index a0b42ff0e..926dd5b5b 100644
--- a/lib/cartopy/tests/test_line_string.py
+++ b/lib/cartopy/tests/test_line_string.py
@@ -8,6 +8,7 @@
 
 import numpy as np
 import pytest
+import shapely
 import shapely.geometry as sgeom
 
 import cartopy.crs as ccrs
@@ -73,6 +74,15 @@ def test_out_of_domain_efficiency(self):
         tgt_proj.project_geometry(line_string, src_proj)
         assert time.time() < cutoff_time, 'Projection took too long'
 
+    @pytest.mark.skipif(shapely.__version__ < "2",
+                        reason="Shapely <2 has an incorrect geom_type ")
+    def test_multi_linestring_return_type(self):
+        # Check that the return type of project_geometry is a MultiLineString
+        # and not an empty list
+        multi_line_string = ccrs.Mercator().project_geometry(
+            sgeom.MultiLineString(), ccrs.PlateCarree())
+        assert isinstance(multi_line_string, sgeom.MultiLineString)
+
 
 class FakeProjection(ccrs.PlateCarree):
     def __init__(self, left_offset=0, right_offset=0):