Fix DST fall-back repeated hour skipped in Arrow.range() (#1162)

arrow/arrow.py

@@ -321,7 +321,27 @@ def fromdatetime(cls, dt: dt_datetime, tzinfo: Optional[TZ_EXPR] = None) -> "Arr
                 tzinfo = timezone.utc
             else:
                 tzinfo = dt.tzinfo
-
+            fold = getattr(dt, "fold", 0)
+        else:
+            # When replacing tzinfo, infer the correct fold by comparing
+            # the original UTC offset to what fold=1 produces in the new tz.
+            # This correctly handles ambiguous times (e.g. DST fall-back) issue #1162.
+            fold = getattr(dt, "fold", 0)
+            if dt.tzinfo is not None and dt.utcoffset() is not None:
+                resolved = cls._get_tzinfo(tzinfo)
+                dt_fold1 = dt_datetime(
+                    dt.year,
+                    dt.month,
+                    dt.day,
+                    dt.hour,
+                    dt.minute,
+                    dt.second,
+                    dt.microsecond,
+                    tzinfo=resolved,
+                    fold=1,
+                )
+                if dt_fold1.utcoffset() == dt.utcoffset():
+                    fold = 1
         return cls(
             dt.year,
             dt.month,
@@ -331,7 +351,7 @@ def fromdatetime(cls, dt: dt_datetime, tzinfo: Optional[TZ_EXPR] = None) -> "Arr
             dt.second,
             dt.microsecond,
             tzinfo,
-            fold=getattr(dt, "fold", 0),
+            fold=fold,
         )
 
     @classmethod

arrow/factory.py

@@ -245,6 +245,11 @@ def get(self, *args: Any, **kwargs: Any) -> Arrow:
             # (str) -> parse @ tzinfo
             elif isinstance(arg, str):
                 dt = parser.DateTimeParser(locale).parse_iso(arg, normalize_whitespace)
+                if tz is not None and dt.tzinfo is not None:
+                    # If the parsed string already has offset info, convert to
+                    # the target timezone (preserving the UTC moment) rather than
+                    # replacing the tzinfo, so ambiguous times are resolved correctly issue #1162.
+                    return self.type.fromdatetime(dt).to(tz)
                 return self.type.fromdatetime(dt, tzinfo=tz)
 
             # (struct_time) -> from struct_time

tests/test_arrow.py

@@ -1141,6 +1141,21 @@ def test_range_over_year_maintains_end_date_across_leap_year(self):
             arrow.Arrow(2016, 2, 29),
         ]
 
+    def test_range_dst_fall_back_includes_repeated_hour(self):
+        # Issue #1162: When iterating over a DST fall-back period, the repeated
+        # hour should not be skipped. A string with an explicit UTC offset and a
+        # named tzinfo kwarg should be converted (not replaced), preserving the
+        # correct UTC moment and fold.
+        import arrow as arrow_module
+
+        dts = arrow_module.get("2021-11-07T01:00:00-05:00", tzinfo="US/Eastern")
+        dte = arrow_module.get("2021-11-07T02:00:00-06:00", tzinfo="US/Eastern")
+        result = list(arrow.Arrow.range("hours", dts, dte))
+        assert len(result) == 3
+        assert result[0].utcoffset().total_seconds() == -5 * 3600
+        assert result[1].utcoffset().total_seconds() == -5 * 3600
+        assert result[2].utcoffset().total_seconds() == -5 * 3600
+
 
 class TestArrowSpanRange:
     def test_year(self):