Fix Duration multiplication by a float dropping years and months

Duration.__mul__ with a float built the result only from
_to_microseconds(), which excludes the years and months components, so
Duration(years=1) * 2.0 returned an empty Duration even though
Duration(years=1) * 2 (int) and Duration(years=1) / 2.0 (float) both keep
them. Scale years and months by the float ratio as well, mirroring the
existing __truediv__ implementation.

Author: gaoflow

src/pendulum/duration.py

@@ -368,7 +368,13 @@ def __mul__(self, other: int | float) -> Self:
             usec = self._to_microseconds()
             a, b = other.as_integer_ratio()
 
-            return self.__class__(0, 0, _divide_and_round(usec * a, b))
+            return self.__class__(
+                0,
+                0,
+                _divide_and_round(usec * a, b),
+                years=_divide_and_round(self._years * a, b),
+                months=_divide_and_round(self._months * a, b),
+            )
 
         return NotImplemented
 

tests/duration/test_arithmetic.py

@@ -27,6 +27,40 @@ def test_multiply():
     assert_duration(mul, 4, 6, 9, 5, 0, 1, 9, 44444)
 
 
+def test_multiply_float():
+    # A float factor must scale years and months just like an int factor (and
+    # like float division already does). Regression: Duration.__mul__ with a
+    # float dropped the years/months components entirely.
+    it = pendulum.duration(
+        years=2, months=3, weeks=4, days=6, seconds=34, microseconds=522222
+    )
+    mul = it * 2.0
+
+    assert isinstance(mul, pendulum.Duration)
+    assert_duration(mul, 4, 6, 9, 5, 0, 1, 9, 44444)
+
+    mul = 2.0 * it
+
+    assert isinstance(mul, pendulum.Duration)
+    assert_duration(mul, 4, 6, 9, 5, 0, 1, 9, 44444)
+
+    # A whole-valued float must match the integer result exactly.
+    it = pendulum.duration(years=1, months=6, days=2, seconds=35, microseconds=522222)
+    by_int = it * 3
+    by_float = it * 3.0
+
+    assert (by_float.years, by_float.months) == (by_int.years, by_int.months)
+    assert by_float.total_seconds() == by_int.total_seconds()
+
+    # A non-integer factor rounds years/months, mirroring float division.
+    it = pendulum.duration(years=2, months=4, days=2, seconds=35, microseconds=522222)
+    mul = it * 1.5
+
+    assert isinstance(mul, pendulum.Duration)
+    assert mul.years == 3
+    assert mul.months == 6
+
+
 def test_divide():
     it = pendulum.duration(days=2, seconds=34, microseconds=522222)
     mul = it / 2