fix(precisedelta): keep sign of negative timedeltas (#379)

src/humanize/time.py

@@ -552,6 +552,16 @@ def precisedelta(
     if date is None:
         return str(value)
 
+    import datetime as dt
+
+    # _date_and_delta() returns an absolute delta; remember the original sign so
+    # negative inputs are not rendered identically to positive ones (#379).
+    is_negative = (
+        value < dt.timedelta(0)
+        if isinstance(value, dt.timedelta)
+        else isinstance(value, (int, float)) and value < 0
+    )
+
     suppress_set = {Unit[s.upper()] for s in suppress}
 
     # Find a suitable minimum unit (it can be greater than the one that the
@@ -652,6 +662,8 @@ def precisedelta(
         ("%d microsecond", "%d microseconds", usecs),
     ]
 
+    sign = "-" if is_negative and any(f[2] for f in fmts) else ""
+
     import math
 
     texts: list[str] = []
@@ -675,12 +687,12 @@ def precisedelta(
             break
 
     if len(texts) == 1:
-        return texts[0]
+        return sign + texts[0]
 
     head = ", ".join(texts[:-1])
     tail = texts[-1]
 
-    return _("%s and %s") % (head, tail)
+    return sign + _("%s and %s") % (head, tail)
 
 
 def _rounding_by_fmt(format: str, value: float) -> float | int:

tests/test_time.py

@@ -875,3 +875,21 @@ def test_time_unit() -> None:
 )
 def test_rounding_by_fmt(fmt: str, value: float, expected: float) -> None:
     assert time._rounding_by_fmt(fmt, value) == pytest.approx(expected)
+
+
+@pytest.mark.parametrize(
+    "val, min_unit, expected",
+    [
+        (dt.timedelta(seconds=-3661), "seconds", "-1 hour, 1 minute and 1 second"),
+        (dt.timedelta(days=-1), "seconds", "-1 day"),
+        (-90, "seconds", "-1 minute and 30 seconds"),
+        (dt.timedelta(seconds=-3661), "minutes", "-1 hour and 1.02 minutes"),
+        (dt.timedelta(seconds=3661), "seconds", "1 hour, 1 minute and 1 second"),
+        (dt.timedelta(0), "seconds", "0 seconds"),
+    ],
+)
+def test_precisedelta_negative_keeps_sign(
+    val: dt.timedelta | int, min_unit: str, expected: str
+) -> None:
+    """Regression for #379: negative deltas must not look like positive ones."""
+    assert humanize.precisedelta(val, minimum_unit=min_unit) == expected