Added docs and test for return_esmpy_regrid_operator #768

Author: mattjbr123

cf/docstring/docstring.py

@@ -651,6 +651,11 @@
                                 operation and define a halo to be
                                 added to the subspaced axes.
                 ==============  ======================================""",
+    # return_esmpy_regrid_operator
+    "{{return_esmpy_regrid_operator: `bool`, optional}}": """return_esmpy_regrid_operator: `bool`, optional
+                If True then do not perform the regridding, rather
+                return the esmpy.Regrid instance that defines the
+                regridding operation.""",                
     # ----------------------------------------------------------------
     # Method description substitutions (4 levels of indentation)
     # ----------------------------------------------------------------

cf/test/test_regrid.py

@@ -791,6 +791,18 @@ def test_Field_regrid_weights_file(self):
                 src.regrids(r, method="linear", weights_file=tmpfile)
             )
 
+    @unittest.skipUnless(esmpy_imported, "Requires esmpy/ESMF package.")
+    def test_return_esmpy_regrid_operator(self):
+        """esmpy regrid operator returns esmpy.api.regrid.Regrid in regrids and regridc"""
+        dst = self.dst
+        src = self.src
+        
+        opers = src.regrids(dst, method="conservative", return_esmpy_regrid_operator=True)
+        operc = src.regridc(dst, method="conservative", return_esmpy_regrid_operator=True)        
+        
+        self.assertIsInstance(opers, esmpy.api.regrid.Regrid)
+        self.assertIsInstance(operc, esmpy.api.regrid.Regrid)
+
 
 if __name__ == "__main__":
     print("Run date:", datetime.datetime.now())