fix: validate the amount in Interval.range

A zero amount made range() yield the same start value forever: the
advance step add(**{unit: i}) with i == 0 never moves, so the loop
condition start <= end never turns false and any consuming for-loop
hangs. A negative amount runs away from the stated end in the opposite
direction, unbounded, for the same missing-validation reason.

Reject non-positive amounts with ValueError, matching the documented
direction handling (the direction itself is applied via add/subtract
and le/ge, so the step magnitude must be positive in both directions).

Fixes #1080

Co-authored-by: rahul05ranjan <11793455+rahul05ranjan@users.noreply.github.com>

Author: rahul05ranjan

CHANGELOG.md

@@ -1,5 +1,10 @@
 # Change Log
 
+## Unreleased
+
+### Fixed
+- `Interval.range()` now raises `ValueError` for a non-positive `amount` instead of silently producing an infinite (amount <= 0... zero repeats the start forever, negative runs away from the end) or unbounded generator [#1080](https://github.com/python-pendulum/pendulum/issues/1080)
+
 ## [3.3.0] - 2026-10-12
 
 ### Added

src/pendulum/interval.py

@@ -288,6 +288,10 @@ def in_words(self, locale: str | None = None, separator: str = " ") -> str:
         return separator.join(parts)
 
     def range(self, unit: str, amount: int = 1) -> Iterator[_T]:
+        if amount <= 0:
+            msg = f"amount must be a positive integer, got {amount!r}"
+            raise ValueError(msg)
+
         method = "add"
         op = operator.le
         if not self._absolute and self.invert:

tests/interval/test_range.py

@@ -1,5 +1,7 @@
 from __future__ import annotations
 
+import pytest
+
 import pendulum
 
 from pendulum.interval import Interval
@@ -117,3 +119,15 @@ def test_range_amount():
     assert_datetime(r[1], 2016, 10, 16, 1, 0, 0)
     assert_datetime(r[2], 2016, 10, 18, 0, 0, 0)
     assert_datetime(r[3], 2016, 10, 20, 0, 0, 0)
+
+
+def test_range_zero_amount_raises():
+    p = Interval(pendulum.datetime(2016, 1, 1), pendulum.datetime(2016, 2, 1))
+    with pytest.raises(ValueError, match="positive integer"):
+        list(p.range("days", 0))
+
+
+def test_range_negative_amount_raises():
+    p = Interval(pendulum.datetime(2016, 1, 1), pendulum.datetime(2016, 2, 1))
+    with pytest.raises(ValueError, match="positive integer"):
+        list(p.range("days", -1))