From 4822bd8cb203863d8d4ac31ba35e1e7eab18e077 Mon Sep 17 00:00:00 2001
From: Justus Magin <keewis@users.noreply.github.com>
Date: Mon, 10 Jun 2024 17:39:17 +0200
Subject: [PATCH] fixes for the `pint` tests (#8983)

* use the `Quantity` constructor instead of multiplying

* manually install `pint` deps into the upstream-dev CI

* stop explicitly installing `pint` dependencies
---
 ci/install-upstream-wheels.sh |  2 ++
 xarray/tests/test_units.py    | 13 +++++--------
 2 files changed, 7 insertions(+), 8 deletions(-)

diff --git a/ci/install-upstream-wheels.sh b/ci/install-upstream-wheels.sh
index b43c6a61ec1..d728768439a 100755
--- a/ci/install-upstream-wheels.sh
+++ b/ci/install-upstream-wheels.sh
@@ -48,6 +48,8 @@ python -m pip install \
     --pre \
     --upgrade \
     pyarrow
+# manually install `pint` to pull in new dependencies
+python -m pip install --upgrade pint
 python -m pip install \
     --no-deps \
     --upgrade \
diff --git a/xarray/tests/test_units.py b/xarray/tests/test_units.py
index 2f11fe688b7..0e8fbe9198b 100644
--- a/xarray/tests/test_units.py
+++ b/xarray/tests/test_units.py
@@ -34,6 +34,7 @@
 # always be treated like ndarrays
 unit_registry = pint.UnitRegistry(force_ndarray_like=True)
 Quantity = unit_registry.Quantity
+no_unit_values = ("none", None)
 
 
 pytestmark = [
@@ -91,17 +92,13 @@ def array_strip_units(array):
 
 
 def array_attach_units(data, unit):
-    if isinstance(data, Quantity):
+    if isinstance(data, Quantity) and data.units != unit:
         raise ValueError(f"cannot attach unit {unit} to quantity {data}")
 
-    try:
-        quantity = data * unit
-    except np.core._exceptions.UFuncTypeError:
-        if isinstance(unit, unit_registry.Unit):
-            raise
-
-        quantity = data
+    if unit in no_unit_values or (isinstance(unit, int) and unit == 1):
+        return data
 
+    quantity = unit_registry.Quantity(data, unit)
     return quantity