fix: PEP 484 prohibits implicit Optional

Problem:

    PEP 484 prohibits implicit Optional. Accordingly, mypy has changed its default to no_implicit_optional=True
    https://github.com/hauntsaninja/no_implicit_optional to automatically upgrade your codebase

Solution:

    ./venv/bin/pip install no_implicit_optional
    ./venv/bin/no_implicit_optional pynvim

pynvim/__init__.py

@@ -6,7 +6,7 @@
 import os
 import sys
 from types import SimpleNamespace as Version
-from typing import List, cast, overload
+from typing import List, Optional, cast, overload
 
 from pynvim.api import Nvim, NvimError
 from pynvim.msgpack_rpc import (ErrorResponse, Session, TTransportType, child_session,
@@ -28,7 +28,7 @@
            'ErrorResponse')
 
 
-def start_host(session: Session = None) -> None:
+def start_host(session: Optional[Session] = None) -> None:
     """Promote the current process into python plugin host for Nvim.
 
     Start msgpack-rpc event loop for `session`, listening for Nvim requests
@@ -101,10 +101,10 @@ def attach(session_type: Literal['stdio']) -> Nvim: ...
 
 def attach(
     session_type: TTransportType,
-    address: str = None,
+    address: Optional[str] = None,
     port: int = 7450,
-    path: str = None,
-    argv: List[str] = None,
+    path: Optional[str] = None,
+    argv: Optional[List[str]] = None,
     decode: Literal[True] = True
 ) -> Nvim:
     """Provide a nicer interface to create python api sessions.

pynvim/api/buffer.py

@@ -13,7 +13,7 @@
 
 
 @overload
-def adjust_index(idx: int, default: int = None) -> int:
+def adjust_index(idx: int, default: Optional[int] = None) -> int:
     ...
 
 
@@ -23,11 +23,11 @@ def adjust_index(idx: Optional[int], default: int) -> int:
 
 
 @overload
-def adjust_index(idx: Optional[int], default: int = None) -> Optional[int]:
+def adjust_index(idx: Optional[int], default: Optional[int] = None) -> Optional[int]:
     ...
 
 
-def adjust_index(idx: Optional[int], default: int = None) -> Optional[int]:
+def adjust_index(idx: Optional[int], default: Optional[int] = None) -> Optional[int]:
     """Convert from python indexing convention to nvim indexing convention."""
     if idx is None:
         return default
@@ -161,7 +161,7 @@ def add_highlight(
         col_start: int = 0,
         col_end: int = -1,
         src_id: int = -1,
-        async_: bool = None,
+        async_: Optional[bool] = None,
         **kwargs: Any
     ) -> int:
         """Add a highlight to the buffer."""
@@ -181,7 +181,7 @@ def clear_highlight(
         src_id: int,
         line_start: int = 0,
         line_end: int = -1,
-        async_: bool = None,
+        async_: Optional[bool] = None,
         **kwargs: Any
     ) -> None:
         """Clear highlights from the buffer."""
@@ -301,7 +301,7 @@ def __iter__(self) -> Iterator[str]:
             yield self._buffer[i]
 
     def append(
-        self, lines: Union[str, bytes, List[Union[str, bytes]]], i: int = None
+        self, lines: Union[str, bytes, List[Union[str, bytes]]], i: Optional[int] = None
     ) -> None:
         i = self._normalize_index(i)
         if i is None:

pynvim/api/common.py

@@ -123,8 +123,8 @@ def __init__(
         self,
         obj: IRemote,
         get_method: str,
-        set_method: str = None,
-        del_method: str = None
+        set_method: Optional[str] = None,
+        del_method: Optional[str] = None
     ):
         """Initialize a RemoteMap with session, getter/setter."""
         self._get = functools.partial(obj.request, get_method)

pynvim/api/nvim.py

@@ -112,7 +112,7 @@ def __init__(
         metadata: Dict[str, Any],
         types: Dict[int, Any],
         decode: TDecodeMode = True,
-        err_cb: Callable[[str], None] = None
+        err_cb: Optional[Callable[[str], None]] = None
     ):
         """Initialize a new Nvim instance. This method is module-private."""
         self._session = session
@@ -142,7 +142,7 @@ def __init__(
             self._err_cb = err_cb
         self.loop = self._session.loop._loop
 
-    def _from_nvim(self, obj: Any, decode: TDecodeMode = None) -> Any:
+    def _from_nvim(self, obj: Any, decode: Optional[TDecodeMode] = None) -> Any:
         if decode is None:
             decode = self._decode
         if type(obj) is ExtType:
@@ -213,8 +213,8 @@ def run_loop(
         self,
         request_cb: Optional[Callable[[str, List[Any]], Any]],
         notification_cb: Optional[Callable[[str, List[Any]], Any]],
-        setup_cb: Callable[[], None] = None,
-        err_cb: Callable[[str], Any] = None
+        setup_cb: Optional[Callable[[], None]] = None,
+        err_cb: Optional[Callable[[str], Any]] = None
     ) -> None:
         """Run the event loop to receive requests and notifications from Nvim.
 
@@ -275,7 +275,7 @@ def with_decode(self, decode: Literal[True] = True) -> 'Nvim':
                     self.metadata, self.types, decode, self._err_cb)
 
     def ui_attach(
-        self, width: int, height: int, rgb: bool = None, **kwargs: Any
+        self, width: int, height: int, rgb: Optional[bool] = None, **kwargs: Any
     ) -> None:
         """Register as a remote UI.
 

pynvim/msgpack_rpc/session.py

@@ -140,7 +140,7 @@ def request(self, method: AnyStr, *args: Any, **kwargs: Any) -> Any:
     def run(self,
             request_cb: Callable[[str, List[Any]], None],
             notification_cb: Callable[[str, List[Any]], None],
-            setup_cb: Callable[[], None] = None) -> None:
+            setup_cb: Optional[Callable[[], None]] = None) -> None:
         """Run the event loop to receive requests and notifications from Nvim.
 
         Like `AsyncSession.run()`, but `request_cb` and `notification_cb` are

pynvim/plugin/decorators.py

@@ -3,7 +3,7 @@
 import inspect
 import logging
 import sys
-from typing import Any, Callable, Dict, TypeVar, Union
+from typing import Any, Callable, Dict, Optional, TypeVar, Union
 
 from pynvim.compat import unicode_errors_default
 
@@ -52,14 +52,14 @@ def dec(f: F) -> F:
 def command(
     name: str,
     nargs: Union[str, int] = 0,
-    complete: str = None,
-    range: Union[str, int] = None,
-    count: int = None,
+    complete: Optional[str] = None,
+    range: Optional[Union[str, int]] = None,
+    count: Optional[int] = None,
     bang: bool = False,
     register: bool = False,
     sync: bool = False,
     allow_nested: bool = False,
-    eval: str = None
+    eval: Optional[str] = None
 ) -> Callable[[F], F]:
     """Tag a function or plugin method as a Nvim command handler."""
     def dec(f: F) -> F:
@@ -112,7 +112,7 @@ def autocmd(
     pattern: str = '*',
     sync: bool = False,
     allow_nested: bool = False,
-    eval: str = None
+    eval: Optional[str] = None
 ) -> Callable[[F], F]:
     """Tag a function or plugin method as a Nvim autocommand handler."""
     def dec(f: F) -> F:
@@ -150,7 +150,7 @@ def function(
     range: Union[bool, str, int] = False,
     sync: bool = False,
     allow_nested: bool = False,
-    eval: str = None
+    eval: Optional[str] = None
 ) -> Callable[[F], F]:
     """Tag a function or plugin method as a Nvim function handler."""
     def dec(f: F) -> F:

pynvim/util.py

@@ -3,10 +3,10 @@
 import sys
 from traceback import format_exception
 from types import SimpleNamespace
-from typing import Any, Dict, Tuple, TypeVar
+from typing import Any, Dict, Optional, Tuple, TypeVar
 
 
-def format_exc_skip(skip: int, limit: int = None) -> str:
+def format_exc_skip(skip: int, limit: Optional[int] = None) -> str:
     """Like traceback.format_exc but allow skipping the first frames."""
     etype, val, tb = sys.exc_info()
     for _ in range(skip):

setup.cfg

@@ -3,7 +3,7 @@ test = pytest
 
 [flake8]
 extend-ignore = D211,E731,D401,W503
-max-line-length = 88
+max-line-length = 100
 per-file-ignores =
   test/*:D1
 application-import-names = pynvim