parse_units instead of parse_expression

pint_xarray/accessors.py

@@ -132,7 +132,7 @@ def _decide_units(units, registry, unit_attribute):
         raise ValueError("no units given")
     elif units is None:
         # TODO option to read and decode units according to CF conventions (see MetPy)?
-        units = registry.parse_expression(unit_attribute).units
+        units = registry.parse_units(unit_attribute)
     elif isinstance(units, Unit):
         # TODO do we have to check what happens if someone passes a Unit instance
         # without creating a unit registry?

pint_xarray/tests/test_conversion.py

@@ -459,3 +459,10 @@ def test_strip_unit_attributes(self, obj, expected):
         assert (
             filter_none_values(conversion.extract_unit_attributes(actual)) == expected
         )
+
+
+class TestParsing:
+    def test_parse_integer_inverse(self):
+        da = DataArray([10], attrs={'units': 'm^-1'})
+        result = da.pint.quantify()
+        assert result.pint.units == pint.Unit('1 / meter')