feat: make TzInfo instantiable without any arguments (#1777)

Author: PrettyWood

python/pydantic_core/_pydantic_core.pyi

@@ -993,7 +993,14 @@ def list_all_errors() -> list[ErrorTypeInfo]:
 class TzInfo(datetime.tzinfo):
     """An `pydantic-core` implementation of the abstract [`datetime.tzinfo`][] class."""
 
-    # def __new__(cls, seconds: float) -> Self: ...
+    def __init__(self, seconds: float = 0.0) -> None:
+        """Initializes the `TzInfo`.
+
+        Arguments:
+            seconds: The offset from UTC in seconds. Defaults to 0.0 (UTC).
+        """
+
+    def __new__(cls, seconds: float = 0.0) -> Self: ...
 
     # Docstrings for attributes sourced from the abstract base class, [`datetime.tzinfo`](https://docs.python.org/3/library/datetime.html#datetime.tzinfo).
 

src/input/datetime.rs

@@ -643,6 +643,7 @@ pub struct TzInfo {
 #[pymethods]
 impl TzInfo {
     #[new]
+    #[pyo3(signature = (seconds = 0.0))]
     fn py_new(seconds: f32) -> PyResult<Self> {
         Self::try_from(seconds.trunc() as i32)
     }

tests/test_tzinfo.py

@@ -213,6 +213,22 @@ def test_offset_boundaries(self):
                 with self.assertRaises(ValueError):
                     TzInfo(delta.total_seconds())
 
+    def test_no_args_constructor(self):
+        # Test that TzInfo can be constructed without arguments
+        tz = TzInfo()
+        self.assertEqual(tz.utcoffset(None), timedelta(0))
+        self.assertEqual(str(tz), 'UTC')
+
+    def test_pickle(self):
+        # Test that TzInfo can be pickled and unpickled
+        for tz in self.ACDT, self.EST, self.UTC:
+            for pickler, unpickler, proto in pickle_choices:
+                with self.subTest(tz=tz, proto=proto):
+                    pickled = pickler.dumps(tz, proto)
+                    unpickled = unpickler.loads(pickled)
+                    self.assertEqual(tz, unpickled)
+                    self.assertEqual(tz.utcoffset(None), unpickled.utcoffset(None))
+
 
 def test_tzinfo_could_be_reused():
     class Model: