Only require typing-extensions if Python < 3.8 (#1873)

Author: hukkinj1

Pipfile

@@ -29,6 +29,6 @@ pathspec = ">=0.6"
 regex = ">=2020.1.8"
 toml = ">=0.10.1"
 typed-ast = "==1.4.2"
-typing_extensions = ">=3.7.4"
+typing_extensions = {"python_version <" = "3.8","version >=" = "3.7.4"}
 black = {editable = true,extras = ["d"],path = "."}
 dataclasses = {"python_version <" = "3.7","version >" = "0.6"}

Pipfile.lock

@@ -75,7 +75,7 @@ def get_long_description() -> str:
         "regex>=2020.1.8",
         "pathspec>=0.6, <1",
         "dataclasses>=0.6; python_version < '3.7'",
-        "typing_extensions>=3.7.4",
+        "typing_extensions>=3.7.4; python_version < '3.8'",
         "mypy_extensions>=0.4.3",
     ],
     extras_require={

setup.py

@@ -42,7 +42,6 @@
     cast,
     TYPE_CHECKING,
 )
-from typing_extensions import Final
 from mypy_extensions import mypyc_attr
 
 from appdirs import user_cache_dir
@@ -61,6 +60,11 @@
 
 from _black_version import version as __version__
 
+if sys.version_info < (3, 8):
+    from typing_extensions import Final
+else:
+    from typing import Final
+
 if TYPE_CHECKING:
     import colorama  # noqa: F401
 

src/black/__init__.py

@@ -1,7 +1,12 @@
 """Token constants (from "token.h")."""
 
+import sys
 from typing import Dict
-from typing_extensions import Final
+
+if sys.version_info < (3, 8):
+    from typing_extensions import Final
+else:
+    from typing import Final
 
 #  Taken from Python (r53757) and modified to include some tokens
 #   originally monkeypatched in by pgen2.tokenize