fix: ensure contiguous spans in span_range with exact=True and month frame (#1185)

arrow/arrow.py

@@ -709,8 +709,16 @@ def span_range(
             for r in _range:
                 yield r.span(frame, bounds=bounds, exact=exact)
 
+        prev_ceil = None
         for r in _range:
             floor, ceil = r.span(frame, bounds=bounds, exact=exact)
+            if prev_ceil is not None:
+                # Ensure consecutive spans are contiguous by using the
+                # previous span's ceiling (+1 microsecond) as the floor,
+                # preventing gaps caused by month-length day clipping.
+                expected_floor = prev_ceil.shift(microseconds=+1)
+                if floor > expected_floor:
+                    floor = expected_floor
             if ceil > end:
                 ceil = end
                 if bounds[1] == ")":
@@ -719,6 +727,7 @@ def span_range(
                 break
             elif floor + relativedelta(microseconds=-1) == end:
                 break
+            prev_ceil = ceil
             yield floor, ceil
 
     @classmethod

tests/test_arrow.py

@@ -1555,6 +1555,27 @@ def test_small_interval_exact_open_bounds(self):
 
         assert result == expected
 
+    def test_exact_month_no_gaps_when_day_clipped(self):
+        """Regression test for #1185: span_range with frame='month' and
+        exact=True must produce contiguous spans even when the start day
+        exceeds the number of days in a shorter month (day clipping)."""
+        result = list(
+            arrow.Arrow.span_range(
+                "month",
+                datetime(2023, 1, 31, tzinfo=ZoneInfo("Europe/Berlin")),
+                datetime(2023, 4, 1, tzinfo=ZoneInfo("Europe/Berlin")),
+                exact=True,
+            )
+        )
+
+        # Spans must be contiguous: each floor == previous ceil + 1 µs
+        for i in range(1, len(result)):
+            prev_ceil = result[i - 1][1]
+            curr_floor = result[i][0]
+            assert curr_floor == prev_ceil.shift(
+                microseconds=+1
+            ), f"Gap between span {i - 1} and {i}"
+
 
 class TestArrowInterval:
     def test_incorrect_input(self):