Fix quantity formatting bug with -0/0

It would only print the unit, no number.

Signed-off-by: Mathias L. Baumann <[email protected]>

Author: Marenz

src/frequenz/sdk/timeseries/_quantities.py

@@ -261,16 +261,17 @@ def __format__(self, __format_spec: str) -> str:
             unit_place = max(self._exponent_unit_map)
         else:
             unit = self._exponent_unit_map[unit_place]
+
         value_str = f"{self._base_value / 10 ** unit_place:.{precision}f}"
 
-        if value_str != "0":
-            stripped = value_str.rstrip("0").rstrip(".")
-        else:
+        if value_str in ("-0", "0"):
             stripped = value_str
+        else:
+            stripped = value_str.rstrip("0").rstrip(".")
 
         if not keep_trailing_zeros:
             value_str = stripped
-        unit_str = unit if stripped != "0" else self._exponent_unit_map[0]
+        unit_str = unit if stripped not in ("-0", "0") else self._exponent_unit_map[0]
         return f"{value_str} {unit_str}"
 
     def __add__(self, other: Self) -> Self:

tests/timeseries/test_quantities.py

@@ -152,6 +152,8 @@ def test_string_representation() -> None:
 
     assert f"{Power.from_watts(0.000124445):.0}" == "0 W"
     assert f"{Energy.from_watt_hours(0.124445):.0}" == "0 Wh"
+    assert f"{Power.from_watts(-0.0):.0}" == "-0 W"
+    assert f"{Power.from_watts(0.0):.0}" == "0 W"
 
 
 def test_isclose() -> None: