Avoid a deprecation warning from numpy 1.25 in crs._safe_pj_transform

lib/cartopy/crs.py

@@ -53,7 +53,22 @@ def _safe_pj_transform(src_crs, tgt_crs, x, y, z=None, trap=True):
     if z is None:
         z = np.zeros_like(x)
 
-    return transformer.transform(x, y, z, errcheck=trap)
+    def _sanitize_scalars(a):
+        # future compatibility with numpy:
+        # pyproj implicitly converts size-1 arrays to scalars, which is
+        # deprecated in numpy 1.25
+        # see https://github.com/numpy/numpy/pull/10615
+        if isinstance(a, np.ndarray) and a.size == 1:
+            return a.item()
+        else:
+            return a
+
+    return transformer.transform(
+        _sanitize_scalars(x),
+        _sanitize_scalars(y),
+        _sanitize_scalars(z),
+        errcheck=trap,
+    )
 
 
 class Globe:

lib/cartopy/tests/crs/test_transform_point.py

@@ -0,0 +1,17 @@
+# Copyright Cartopy Contributors
+#
+# This file is part of Cartopy and is released under the LGPL license.
+# See COPYING and COPYING.LESSER in the root of the repository for full
+# licensing details.
+import warnings
+
+import cartopy.crs as ccrs
+
+
+def test_transform_point():
+    # see https://github.com/SciTools/cartopy/pull/2194
+    p = ccrs.PlateCarree()
+    p2 = ccrs.Mercator()
+    with warnings.catch_warnings():
+        warnings.simplefilter("error")
+        p2.transform_point(1, 2, p)