Add the ability to disable timezone extension

Author: sdispater

pendulum/tz/__init__.py

@@ -20,7 +20,7 @@
 _tz_cache = {}
 
 
-def timezone(name):  # type: (Union[str, int]) -> _Timezone
+def timezone(name, extended=True):  # type: (Union[str, int]) -> _Timezone
     """
     Return a Timezone instance given its name.
     """
@@ -33,7 +33,7 @@ def timezone(name):  # type: (Union[str, int]) -> _Timezone
     if name in _tz_cache:
         return _tz_cache[name]
 
-    tz = _Timezone(name)
+    tz = _Timezone(name, extended=extended)
     _tz_cache[name] = tz
 
     return tz

pendulum/tz/timezone.py

@@ -26,8 +26,8 @@ class Timezone(tzinfo):
     >>> tz = Timezone('Europe/Paris')
     """
 
-    def __init__(self, name):  # type: (str) -> None
-        tz = read(name)
+    def __init__(self, name, extended=True):  # type: (str) -> None
+        tz = read(name, extend=extended)
 
         self._name = name
         self._transitions = tz.transitions

pendulum/tz/zoneinfo/__init__.py

@@ -1,18 +1,16 @@
 from .reader import Reader
 from .timezone import Timezone
 
-_reader = Reader()
 
-
-def read(name):  # type: (str) -> Timezone
+def read(name, extend=True):  # type: (str) -> Timezone
     """
     Read the zoneinfo structure for a given timezone name.
     """
-    return _reader.read_for(name)
+    return Reader(extend=extend).read_for(name)
 
 
-def read_file(path):  # type: (str) -> Timezone:
+def read_file(path, extend=True):  # type: (str) -> Timezone
     """
     Read the zoneinfo structure for a given path.
     """
-    return _reader.read(path)
+    return Reader(extend=extend).read(path)

pendulum/tz/zoneinfo/reader.py

@@ -35,6 +35,9 @@ class Reader:
     Reads compiled zoneinfo TZif (\0, 2 or 3) files.
     """
 
+    def __init__(self, extend=True):  # type: (bool) -> None
+        self._extend = extend
+
     def read_for(self, timezone):  # type: (str) -> Timezone
         """
         Read the zoneinfo structure for a given timezone name.
@@ -147,7 +150,7 @@ def _parse(self, fd):  # type: (...) -> Timezone
                 Transition(0, types[0], None)
             )
 
-        return Timezone(transitions, posix_rule=trule)
+        return Timezone(transitions, posix_rule=trule, extended=self._extend)
 
     def _parse_header(self, fd):  # type: (...) -> header
         buff = self._check_read(fd, 44)

pendulum/tz/zoneinfo/timezone.py

@@ -14,11 +14,13 @@ class Timezone:
     def __init__(self,
                  transitions,      # type: List[Transition]
                  posix_rule=None,  # type: Union[PosixTimezone, None]
+                 extended=True     # type: bool
                  ):
         self._posix_rule = posix_rule
         self._transitions = transitions
 
-        self._extends()
+        if extended:
+            self._extends()
 
     @property
     def transitions(self):  # type: () -> List[Transition]

tests/tz/test_timezone.py

@@ -10,6 +10,15 @@
 from ..conftest import assert_datetime
 
 
+@pytest.fixture(autouse=True)
+def setup():
+    pendulum.tz._tz_cache = {}
+
+    yield
+
+    pendulum.tz._tz_cache = {}
+
+
 @pytest.mark.skipif(not PY36, reason='fold attribute only present in Python 3.6+')
 def test_basic_convert():
     dt = datetime(2016, 6, 1, 12, 34, 56, 123456, fold=1)
@@ -497,6 +506,48 @@ def test_timezones_are_extended():
     assert dt.dst() == timedelta()
 
 
+def test_timezones_extension_can_be_disabled():
+    tz = pendulum.timezone('Europe/Paris', extended=False)
+    dt = tz.convert(pendulum.naive(2134, 2, 13, 1))
+
+    assert_datetime(dt, 2134, 2, 13, 1)
+    assert dt.utcoffset().total_seconds() == 3600
+    assert dt.dst() == timedelta()
+
+    dt = tz.convert(
+        pendulum.naive(2134, 3, 28, 2, 30),
+        dst_rule=pendulum.POST_TRANSITION
+    )
+
+    assert_datetime(dt, 2134, 3, 28, 2, 30)
+    assert dt.utcoffset().total_seconds() == 3600
+    assert dt.dst() == timedelta()
+
+    dt = tz.convert(pendulum.naive(2134, 7, 11, 2, 30))
+
+    assert_datetime(dt, 2134, 7, 11, 2, 30)
+    assert dt.utcoffset().total_seconds() == 3600
+    assert dt.dst() == timedelta()
+
+    dt = tz.convert(
+        pendulum.naive(2134, 10, 31, 2, 30),
+        dst_rule=pendulum.PRE_TRANSITION
+    )
+
+    assert_datetime(dt, 2134, 10, 31, 2, 30)
+    assert dt.utcoffset().total_seconds() == 3600
+    assert dt.dst() == timedelta()
+
+    dt = tz.convert(
+        pendulum.naive(2134, 10, 31, 2, 30),
+        dst_rule=pendulum.POST_TRANSITION
+    )
+
+    assert_datetime(dt, 2134, 10, 31, 2, 30)
+    assert dt.utcoffset().total_seconds() == 3600
+    assert dt.dst() == timedelta()
+
+
 def test_repr():
     tz = timezone('Europe/Paris')