backup properties instead of potentially empty private attributes

Author: chenkasirer

src/compas/tolerance.py

@@ -398,14 +398,14 @@ def temporary(
         """
         # Save current state
         saved = {
-            "unit": self._unit,
-            "absolute": self._absolute,
-            "relative": self._relative,
-            "angular": self._angular,
-            "approximation": self._approximation,
-            "precision": self._precision,
-            "lineardeflection": self._lineardeflection,
-            "angulardeflection": self._angulardeflection,
+            "unit": self.unit,
+            "absolute": self.absolute,
+            "relative": self.relative,
+            "angular": self.angular,
+            "approximation": self.approximation,
+            "precision": self.precision,
+            "lineardeflection": self.lineardeflection,
+            "angulardeflection": self.angulardeflection,
         }
         try:
             # Apply temporary changes

tests/compas/test_tolerance.py

@@ -62,6 +62,16 @@ def test_tolerance_temporary_restores_on_exception():
     assert TOL.absolute == original
 
 
+def test_tolerance_temporary_restores_unit():
+    """Test that temporary() restores values even if an exception occurs."""
+    original = TOL.unit
+
+    with TOL.temporary(unit="MM"):
+        assert TOL.unit == "MM"
+
+    assert TOL.unit == original
+
+
 def test_tolerance_format_number():
     assert TOL.format_number(0, precision=3) == "0.000"
     assert TOL.format_number(0.5, precision=3) == "0.500"