Change method return types to Self where suitable (#3364)

changelog/3363.bugfix.rst

@@ -0,0 +1 @@
+Consistently used ``typing.Self`` for return types representing copying actions.

src/urllib3/_collections.py

@@ -427,7 +427,7 @@ def _copy_from(self, other: HTTPHeaderDict) -> None:
             val = other.getlist(key)
             self._container[key.lower()] = [key, *val]
 
-    def copy(self) -> HTTPHeaderDict:
+    def copy(self) -> Self:
         clone = type(self)()
         clone._copy_from(self)
         return clone
@@ -462,7 +462,7 @@ def __ior__(self, other: object) -> HTTPHeaderDict:
         self.extend(maybe_constructable)
         return self
 
-    def __or__(self, other: object) -> HTTPHeaderDict:
+    def __or__(self, other: object) -> Self:
         # Supports merging header dicts using operator |
         # combining items with add instead of __setitem__
         maybe_constructable = ensure_can_construct_http_header_dict(other)
@@ -472,7 +472,7 @@ def __or__(self, other: object) -> HTTPHeaderDict:
         result.extend(maybe_constructable)
         return result
 
-    def __ror__(self, other: object) -> HTTPHeaderDict:
+    def __ror__(self, other: object) -> Self:
         # Supports merging header dicts using operator | when other is on left side
         # combining items with add instead of __setitem__
         maybe_constructable = ensure_can_construct_http_header_dict(other)

src/urllib3/connectionpool.py

@@ -55,14 +55,14 @@
     import ssl
     from typing import Literal
 
+    from typing_extensions import Self
+
     from ._base_connection import BaseHTTPConnection, BaseHTTPSConnection
 
 log = logging.getLogger(__name__)
 
 _TYPE_TIMEOUT = typing.Union[Timeout, float, _TYPE_DEFAULT, None]
 
-_SelfT = typing.TypeVar("_SelfT")
-
 
 # Pool objects
 class ConnectionPool:
@@ -95,7 +95,7 @@ def __init__(self, host: str, port: int | None = None) -> None:
     def __str__(self) -> str:
         return f"{type(self).__name__}(host={self.host!r}, port={self.port!r})"
 
-    def __enter__(self: _SelfT) -> _SelfT:
+    def __enter__(self) -> Self:
         return self
 
     def __exit__(

src/urllib3/poolmanager.py

@@ -28,6 +28,8 @@
     import ssl
     from typing import Literal
 
+    from typing_extensions import Self
+
 __all__ = ["PoolManager", "ProxyManager", "proxy_from_url"]
 
 
@@ -51,8 +53,6 @@
 # http.client.HTTPConnection & http.client.HTTPSConnection in Python 3.7
 _DEFAULT_BLOCKSIZE = 16384
 
-_SelfT = typing.TypeVar("_SelfT")
-
 
 class PoolKey(typing.NamedTuple):
     """
@@ -214,7 +214,7 @@ def __init__(
         self.pool_classes_by_scheme = pool_classes_by_scheme
         self.key_fn_by_scheme = key_fn_by_scheme.copy()
 
-    def __enter__(self: _SelfT) -> _SelfT:
+    def __enter__(self) -> Self:
         return self
 
     def __exit__(

src/urllib3/util/retry.py

@@ -21,6 +21,8 @@
 from .util import reraise
 
 if typing.TYPE_CHECKING:
+    from typing_extensions import Self
+
     from ..connectionpool import ConnectionPool
     from ..response import BaseHTTPResponse
 
@@ -240,7 +242,7 @@ def __init__(
         )
         self.backoff_jitter = backoff_jitter
 
-    def new(self, **kw: typing.Any) -> Retry:
+    def new(self, **kw: typing.Any) -> Self:
         params = dict(
             total=self.total,
             connect=self.connect,
@@ -429,7 +431,7 @@ def increment(
         error: Exception | None = None,
         _pool: ConnectionPool | None = None,
         _stacktrace: TracebackType | None = None,
-    ) -> Retry:
+    ) -> Self:
         """Return a new Retry object with incremented retry counters.
 
         :param response: A response object, or None, if the server did not

src/urllib3/util/ssltransport.py

@@ -10,10 +10,11 @@
 if typing.TYPE_CHECKING:
     from typing import Literal
 
+    from typing_extensions import Self
+
     from .ssl_ import _TYPE_PEER_CERT_RET, _TYPE_PEER_CERT_RET_DICT
 
 
-_SelfT = typing.TypeVar("_SelfT", bound="SSLTransport")
 _WriteBuffer = typing.Union[bytearray, memoryview]
 _ReturnValue = typing.TypeVar("_ReturnValue")
 
@@ -70,7 +71,7 @@ def __init__(
         # Perform initial handshake.
         self._ssl_io_loop(self.sslobj.do_handshake)
 
-    def __enter__(self: _SelfT) -> _SelfT:
+    def __enter__(self) -> Self:
         return self
 
     def __exit__(self, *_: typing.Any) -> None: