Add Optional[] for all remaining cases of x: <type> = None (#1424)

gvanrossum · matthiaskramm · commit 350563223f01 · 2017-06-21T10:50:21.000-07:00
* Final round of adding Optional[] to type of arguments with default = None
* Update Travis to use --no-implicit-optionals and clarify CONTRIBUTING.md
diff --git a/.travis.yml b/.travis.yml
@@ -8,7 +8,7 @@ matrix:
     - python: "3.6"
       env: TEST_CMD="./tests/mypy_selftest.py"
     - python: "3.5"
-      env: TEST_CMD="./tests/mypy_test.py"
+      env: TEST_CMD="./tests/mypy_test.py --no-implicit-optional"
     - python: "2.7"
       env: TEST_CMD="./tests/pytype_test.py --num-parallel=4"
 
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
@@ -135,7 +135,8 @@ rule is that they should be as concise as possible.  Specifically:
   names, or methods and fields within a single class;
 * use a single blank line between top-level class definitions, or none
   if the classes are very small;
-* do not use docstrings.
+* do not use docstrings;
+* for arguments with a type and a default, use spaces around the `=`.
 
 Imports in stubs are considered private (not part of the exported API)
 unless:
@@ -144,6 +145,14 @@ unless:
 * they use the form ``from library import *`` which means all names
   from that library are exported.
 
+For arguments with type and a default value of `None`, PEP 484
+prescribes that the type automatically becomes `Optional`.  However we
+prefer explicit over implicit in this case, and require the explicit
+`Optional[]` around the type.  The mypy tests enforce this (through
+the use of --no-implicit-optional) and the error looks like
+`Incompatible types in assignment (expression has type None, variable
+has type "Blah") `.
+
 Stub files support forward references natively.  In other words, the
 order of class declarations and type aliases does not matter in
 a stub file.  You can also use the name of the class within its own
diff --git a/stdlib/3.4/asyncio/locks.pyi b/stdlib/3.4/asyncio/locks.pyi
@@ -37,7 +37,7 @@ class Event:
     def wait(self) -> Generator[Any, None, bool]: ...
 
 class Condition(_ContextManagerMixin):
-    def __init__(self, lock: Lock = None, *, loop: Optional[AbstractEventLoop] = ...) -> None: ...
+    def __init__(self, lock: Optional[Lock] = None, *, loop: Optional[AbstractEventLoop] = ...) -> None: ...
     def locked(self) -> bool: ...
     @coroutine
     def acquire(self) -> Generator[Any, None, bool]: ...
diff --git a/stdlib/3/builtins.pyi b/stdlib/3/builtins.pyi
diff --git a/stdlib/3/configparser.pyi b/stdlib/3/configparser.pyi
@@ -80,9 +80,9 @@ class RawConfigParser(_parser):
     def has_option(self, section: str, option: str) -> bool: ...
 
     def read(self, filenames: Union[str, Sequence[str]],
-             encoding: str = None) -> List[str]: ...
+             encoding: Optional[str] = None) -> List[str]: ...
 
-    def read_file(self, f: Iterable[str], source: str = None) -> None: ...
+    def read_file(self, f: Iterable[str], source: Optional[str] = None) -> None: ...
 
     def read_string(self, string: str, source: str = ...) -> None: ...
 
@@ -117,16 +117,16 @@ class RawConfigParser(_parser):
 
 class ConfigParser(RawConfigParser):
     def __init__(self,
-                 defaults: _section = None,
+                 defaults: Optional[_section] = None,
                  dict_type: Mapping[str, str] = ...,
                  allow_no_value: bool = ...,
                  delimiters: Sequence[str] = ...,
                  comment_prefixes: Sequence[str] = ...,
-                 inline_comment_prefixes: Sequence[str] = None,
+                 inline_comment_prefixes: Optional[Sequence[str]] = None,
                  strict: bool = ...,
                  empty_lines_in_values: bool = ...,
                  default_section: str = ...,
-                 interpolation: Interpolation = None,
+                 interpolation: Optional[Interpolation] = None,
                  converters: _converters = ...) -> None: ...
 
 class SafeConfigParser(ConfigParser): ...
diff --git a/stdlib/3/getpass.pyi b/stdlib/3/getpass.pyi
@@ -1,9 +1,9 @@
 # Stubs for getpass
 
-from typing import TextIO
+from typing import Optional, TextIO
 
 
-def getpass(prompt: str = ..., stream: TextIO = None) -> str: ...
+def getpass(prompt: str = ..., stream: Optional[TextIO] = None) -> str: ...
 
 
 def getuser() -> str: ...
diff --git a/stdlib/3/importlib/__init__.pyi b/stdlib/3/importlib/__init__.pyi
@@ -4,14 +4,15 @@ import sys
 import types
 from typing import Any, Mapping, Optional, Sequence
 
-def __import__(name: str, globals: Mapping[str, Any] = None,
-               locals: Mapping[str, Any] = None, fromlist: Sequence[str] = ...,
+def __import__(name: str, globals: Optional[Mapping[str, Any]] = None,
+               locals: Optional[Mapping[str, Any]] = None,
+               fromlist: Sequence[str] = ...,
                level: int = ...) -> types.ModuleType: ...
 
-def import_module(name: str, package: str = None) -> types.ModuleType: ...
+def import_module(name: str, package: Optional[str] = None) -> types.ModuleType: ...
 
 if sys.version_info >= (3, 3):
-    def find_loader(name: str, path: str = None) -> Optional[Loader]: ...
+    def find_loader(name: str, path: Optional[str] = None) -> Optional[Loader]: ...
 
     def invalidate_caches() -> None: ...
 
diff --git a/stdlib/3/importlib/abc.pyi b/stdlib/3/importlib/abc.pyi
@@ -19,7 +19,7 @@ class Finder(metaclass=ABCMeta):
     # easier to simply ignore that this method exists.
     # @abstractmethod
     # def find_module(self, fullname: str,
-    #                 path: Sequence[_Path] = None) -> Optional[Loader]: ...
+    #                 path: Optional[Sequence[_Path]] = None) -> Optional[Loader]: ...
 
 class ResourceLoader(Loader):
     @abstractmethod
@@ -64,7 +64,7 @@ if sys.version_info >= (3, 3):
             # Not defined on the actual class, but expected to exist.
             def find_spec(
                 self, fullname: str, path: Optional[Sequence[_Path]],
-                target: types.ModuleType = None
+                target: Optional[types.ModuleType] = None
             ) -> Optional[ModuleSpec]:
                 ...
 
@@ -78,7 +78,7 @@ if sys.version_info >= (3, 3):
             # Not defined on the actual class, but expected to exist.
             def find_spec(
                 self, fullname: str,
-                target: types.ModuleType = None
+                target: Optional[types.ModuleType] = None
             ) -> Optional[ModuleSpec]: ...
 
     class FileLoader(ResourceLoader, ExecutionLoader):
diff --git a/stdlib/3/importlib/machinery.pyi b/stdlib/3/importlib/machinery.pyi
@@ -22,7 +22,7 @@ if sys.version_info >= (3, 3):
             @classmethod
             def find_spec(cls, fullname: str,
                           path: Optional[Sequence[importlib.abc._Path]],
-                          target: types.ModuleType = None) -> Optional[ModuleSpec]:
+                          target: Optional[types.ModuleType] = None) -> Optional[ModuleSpec]:
                 ...
         # InspectLoader
         @classmethod
@@ -79,7 +79,7 @@ if sys.version_info >= (3, 3):
             @classmethod
             def find_spec(cls, fullname: str,
                           path: Optional[Sequence[importlib.abc._Path]],
-                          target: types.ModuleType = None) -> Optional[ModuleSpec]:
+                          target: Optional[types.ModuleType] = None) -> Optional[ModuleSpec]:
                 ...
         # InspectLoader
         @classmethod
@@ -136,7 +136,7 @@ if sys.version_info >= (3, 3):
             @classmethod
             def find_spec(cls, fullname: str,
                           path: Optional[Sequence[importlib.abc._Path]],
-                          target: types.ModuleType = None) -> Optional[ModuleSpec]:
+                          target: Optional[types.ModuleType] = None) -> Optional[ModuleSpec]:
                 ...
 else:
     class WindowsRegisteryFinder:
diff --git a/stdlib/3/importlib/util.pyi b/stdlib/3/importlib/util.pyi
@@ -20,22 +20,22 @@ if sys.version_info >= (3, 3):
 if sys.version_info >= (3, 4):
     MAGIC_NUMBER = ...  # type: bytes
 
-    def cache_from_source(path: str, debug_override: bool = None, *,
-                          optimization: Any = None) -> str: ...
+    def cache_from_source(path: str, debug_override: Optional[bool] = None, *,
+                          optimization: Optional[Any] = None) -> str: ...
     def source_from_cache(path: str) -> str: ...
     def decode_source(source_bytes: bytes) -> str: ...
     def find_spec(
-        name: str, package: str = None
+        name: str, package: Optional[str] = None
     ) -> importlib.machinery.ModuleSpec: ...
     def spec_from_loader(
         name: str, loader: Optional[importlib.abc.Loader], *,
-        origin: str = None, loader_state: Any = None,
-        is_package: bool = None
+        origin: Optional[str] = None, loader_state: Optional[Any] = None,
+        is_package: Optional[bool] = None
     ) -> importlib.machinery.ModuleSpec: ...
     def spec_from_file_location(
         name: str, location: str, *,
-        loader: importlib.abc.Loader = None,
-        submodule_search_locations: List[str]=None
+        loader: Optional[importlib.abc.Loader] = None,
+        submodule_search_locations: Optional[List[str]] = None
     ) -> importlib.machinery.ModuleSpec: ...
 
 if sys.version_info >= (3, 5):
diff --git a/stdlib/3/io.pyi b/stdlib/3/io.pyi
@@ -106,8 +106,8 @@ class BytesIO(BinaryIO):
     def __iter__(self) -> Iterator[bytes]: ...
     def __next__(self) -> bytes: ...
     def __enter__(self) -> 'BytesIO': ...
-    def __exit__(self, t: type = None, value: BaseException = None,
-                 traceback: Any = None) -> bool: ...
+    def __exit__(self, t: Optional[type] = None, value: Optional[BaseException] = None,
+                 traceback: Optional[Any] = None) -> bool: ...
     def close(self) -> None: ...
     def fileno(self) -> int: ...
     def flush(self) -> None: ...
@@ -210,8 +210,8 @@ class TextIOWrapper(TextIO):
         write_through: bool = ...
     ) -> None: ...
     # copied from IOBase
-    def __exit__(self, t: type = None, value: BaseException = None,
-                 traceback: Any = None) -> bool: ...
+    def __exit__(self, t: Optional[type] = None, value: Optional[BaseException] = None,
+                 traceback: Optional[Any] = None) -> bool: ...
     def close(self) -> None: ...
     def fileno(self) -> int: ...
     def flush(self) -> None: ...
diff --git a/stdlib/3/json/decoder.pyi b/stdlib/3/json/decoder.pyi
@@ -1,5 +1,5 @@
 import sys
-from typing import Any, Callable, Dict, List, Tuple
+from typing import Any, Callable, Dict, List, Optional, Tuple
 
 if sys.version_info >= (3, 5):
     class JSONDecodeError(ValueError):
@@ -18,11 +18,11 @@ class JSONDecoder:
     strict = ...  # type: bool
     object_pairs_hook = None  # type: Callable[[List[Tuple[str, Any]]], Any]
 
-    def __init__(self, object_hook: Callable[[Dict[str, Any]], Any]=None,
-            parse_float: Callable[[str], Any]=None,
-            parse_int: Callable[[str], Any]=None,
-            parse_constant: Callable[[str], Any]=None,
-            strict: bool=True,
-            object_pairs_hook: Callable[[List[Tuple[str, Any]]], Any]=None) -> None: ...
+    def __init__(self, object_hook: Optional[Callable[[Dict[str, Any]], Any]] = None,
+            parse_float: Optional[Callable[[str], Any]] = None,
+            parse_int: Optional[Callable[[str], Any]] = None,
+            parse_constant: Optional[Callable[[str], Any]] = None,
+            strict: bool = True,
+            object_pairs_hook: Optional[Callable[[List[Tuple[str, Any]]], Any]] = None) -> None: ...
     def decode(self, s: str) -> Any: ...
-    def raw_decode(self, s: str, idx: int=...) -> Tuple[Any, int]: ...
+    def raw_decode(self, s: str, idx: int = ...) -> Tuple[Any, int]: ...
diff --git a/stdlib/3/json/encoder.pyi b/stdlib/3/json/encoder.pyi
@@ -1,4 +1,4 @@
-from typing import Any, Callable, Iterator, Tuple
+from typing import Any, Callable, Iterator, Optional, Tuple
 
 class JSONEncoder:
     item_separator = ...  # type: str
@@ -11,10 +11,10 @@ class JSONEncoder:
     sort_keys = ...  # type: bool
     indent = None  # type: int
 
-    def __init__(self, skipkeys: bool=..., ensure_ascii: bool=...,
-            check_circular: bool=..., allow_nan: bool=..., sort_keys: bool=...,
-            indent: int=None, separators: Tuple[str, str]=None, default: Callable=None) -> None: ...
+    def __init__(self, skipkeys: bool = ..., ensure_ascii: bool = ...,
+            check_circular: bool = ..., allow_nan: bool = ..., sort_keys: bool = ...,
+            indent: Optional[int] = None, separators: Optional[Tuple[str, str]] = None, default: Optional[Callable] = None) -> None: ...
 
     def default(self, o: Any) -> Any: ...
     def encode(self, o: Any) -> str: ...
-    def iterencode(self, o: Any, _one_shot: bool=False) -> Iterator[str]: ...
+    def iterencode(self, o: Any, _one_shot: bool = False) -> Iterator[str]: ...
diff --git a/stdlib/3/multiprocessing/__init__.pyi b/stdlib/3/multiprocessing/__init__.pyi
@@ -25,7 +25,7 @@ class Pool():
                  initializer: Optional[Callable[..., None]] = ...,
                  initargs: Iterable[Any] = ...,
                  maxtasksperchild: Optional[int] = ...,
-                 context: Any = None) -> None: ...
+                 context: Optional[Any] = None) -> None: ...
     def apply(self,
               func: Callable[..., Any],
               args: Iterable[Any] = ...,
@@ -34,17 +34,17 @@ class Pool():
                 func: Callable[..., Any],
                 args: Iterable[Any] = ...,
                 kwds: Dict[str, Any] = ...,
-                callback: Callable[..., None] = None,
-                error_callback: Callable[[BaseException], None] = None) -> AsyncResult: ...
+                callback: Optional[Callable[..., None]] = None,
+                error_callback: Optional[Callable[[BaseException], None]] = None) -> AsyncResult: ...
     def map(self,
             func: Callable[..., Any],
             iterable: Iterable[Any] = ...,
             chunksize: Optional[int] = ...) -> List[Any]: ...
     def map_async(self, func: Callable[..., Any],
                   iterable: Iterable[Any] = ...,
                   chunksize: Optional[int] = ...,
-                  callback: Callable[..., None] = None,
-                  error_callback: Callable[[BaseException], None] = None) -> AsyncResult: ...
+                  callback: Optional[Callable[..., None]] = None,
+                  error_callback: Optional[Callable[[BaseException], None]] = None) -> AsyncResult: ...
     def imap(self,
              func: Callable[..., Any],
              iterable: Iterable[Any] = ...,
@@ -61,8 +61,8 @@ class Pool():
                       func: Callable[..., Any],
                       iterable: Iterable[Iterable[Any]] = ...,
                       chunksize: Optional[int] = ...,
-                      callback: Callable[..., None] = None,
-                      error_callback: Callable[[BaseException], None] = None) -> AsyncResult: ...
+                      callback: Optional[Callable[..., None]] = None,
+                      error_callback: Optional[Callable[[BaseException], None]] = None) -> AsyncResult: ...
     def close(self) -> None: ...
     def terminate(self) -> None: ...
     def join(self) -> None: ...
diff --git a/stdlib/3/multiprocessing/pool.pyi b/stdlib/3/multiprocessing/pool.pyi
@@ -22,17 +22,17 @@ class ThreadPool():
                 func: Callable[..., Any],
                 args: Iterable[Any] = ...,
                 kwds: Dict[str, Any] = ...,
-                callback: Callable[..., None] = None,
-                error_callback: Callable[[BaseException], None] = None) -> AsyncResult: ...
+                callback: Optional[Callable[..., None]] = None,
+                error_callback: Optional[Callable[[BaseException], None]] = None) -> AsyncResult: ...
     def map(self,
             func: Callable[..., Any],
             iterable: Iterable[Any] = ...,
             chunksize: Optional[int] = None) -> List[Any]: ...
     def map_async(self, func: Callable[..., Any],
                   iterable: Iterable[Any] = ...,
-                  chunksize: Optional[int] = None,
-                  callback: Callable[..., None] = None,
-                  error_callback: Callable[[BaseException], None] = None) -> AsyncResult: ...
+                  chunksize: Optional[Optional[int]] = None,
+                  callback: Optional[Callable[..., None]] = None,
+                  error_callback: Optional[Callable[[BaseException], None]] = None) -> AsyncResult: ...
     def imap(self,
              func: Callable[..., Any],
              iterable: Iterable[Any] = ...,
@@ -49,8 +49,8 @@ class ThreadPool():
                       func: Callable[..., Any],
                       iterable: Iterable[Iterable[Any]] = ...,
                       chunksize: Optional[int] = None,
-                      callback: Callable[..., None] = None,
-                      error_callback: Callable[[BaseException], None] = None) -> AsyncResult: ...
+                      callback: Optional[Callable[..., None]] = None,
+                      error_callback: Optional[Callable[[BaseException], None]] = None) -> AsyncResult: ...
     def close(self) -> None: ...
     def terminate(self) -> None: ...
     def join(self) -> None: ...
diff --git a/stdlib/3/unittest/mock.pyi b/stdlib/3/unittest/mock.pyi
diff --git a/third_party/3/six/__init__.pyi b/third_party/3/six/__init__.pyi
diff --git a/third_party/3/werkzeug/wrappers.pyi b/third_party/3/werkzeug/wrappers.pyi
