Fix issue #1494: pxd files should be sorted by default

CHANGELOG.md

@@ -6,6 +6,7 @@ Find out more about isort's release policy [here](https://pycqa.github.io/isort/
 
 ### 5.6.0 TBD
   - Implemented #1433: Provide helpful feedback in case a custom config file is specified without a configuration.
+  - Implemented #1494: Default to sorting imports within `.pxd` files.
   - Improved handling of unsupported configuration option errors (see #1475).
   - Fixed #1463: Better interactive documentation for future option.
   - Fixed #1461: Quiet config option not respected by file API in some circumstances.

isort/settings.py

@@ -31,7 +31,7 @@
 from .wrap_modes import from_string as wrap_mode_from_string
 
 _SHEBANG_RE = re.compile(br"^#!.*\bpython[23w]?\b")
-SUPPORTED_EXTENSIONS = frozenset({"py", "pyi", "pyx"})
+SUPPORTED_EXTENSIONS = frozenset({"py", "pyi", "pyx", "pxd"})
 BLOCKED_EXTENSIONS = frozenset({"pex"})
 FILE_SKIP_COMMENTS: Tuple[str, ...] = (
     "isort:" + "skip_file",

tests/unit/test_settings.py

@@ -49,6 +49,7 @@ def test_is_supported_filetype(self):
         assert self.instance.is_supported_filetype("file.py")
         assert self.instance.is_supported_filetype("file.pyi")
         assert self.instance.is_supported_filetype("file.pyx")
+        assert self.instance.is_supported_filetype("file.pxd")
         assert not self.instance.is_supported_filetype("file.pyc")
         assert not self.instance.is_supported_filetype("file.txt")
         assert not self.instance.is_supported_filetype("file.pex")