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bpo-39019: Implement missing __class_getitem__ for subprocess classes #17558

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Merged
ilevkivskyi merged 2 commits into from
Dec 30, 2019
Merged

bpo-39019: Implement missing __class_getitem__ for subprocess classes #17558

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b6fd2b5
Implement missing __class_getitem__ for subprocess classes
isidentical Dec 27, 2019
74162ec
clarify purpose of __class_getitems__
isidentical Dec 27, 2019
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24 changes: 24 additions & 0 deletions Lib/subprocess.py
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Original file line number Diff line number Diff line change
Expand Up @@ -446,6 +446,19 @@ def __repr__(self):
args.append('stderr={!r}'.format(self.stderr))
return "{}({})".format(type(self).__name__, ', '.join(args))

def __class_getitem__(cls, type):
"""Provide minimal support for using this class as generic
(for example in type annotations).

See PEP 484 and PEP 560 for more details. For example,
`CompletedProcess[bytes]` is a valid expression at runtime
(type argument `bytes` indicates the type used for stdout).
Note, no type checking happens at runtime, but a static type
checker can be used.
"""
return cls


def check_returncode(self):
"""Raise CalledProcessError if the exit code is non-zero."""
if self.returncode:
Expand Down Expand Up @@ -987,6 +1000,17 @@ def __repr__(self):
obj_repr = obj_repr[:76] + "...>"
return obj_repr

def __class_getitem__(cls, type):
"""Provide minimal support for using this class as generic
(for example in type annotations).

See PEP 484 and PEP 560 for more details. For example, `Popen[bytes]`
is a valid expression at runtime (type argument `bytes` indicates the
type used for stdout). Note, no type checking happens at runtime, but
a static type checker can be used.
"""
return cls

@property
def universal_newlines(self):
# universal_newlines as retained as an alias of text_mode for API
Expand Down
3 changes: 3 additions & 0 deletions Lib/test/test_subprocess.py
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Expand Up @@ -1437,6 +1437,9 @@ def test_file_not_found_with_bad_cwd(self):
subprocess.Popen(['exit', '0'], cwd='/some/nonexistent/directory')
self.assertEqual(c.exception.filename, '/some/nonexistent/directory')

def test_class_getitems(self):
self.assertIs(subprocess.Popen[bytes], subprocess.Popen)
self.assertIs(subprocess.CompletedProcess[str], subprocess.CompletedProcess)

class RunFuncTestCase(BaseTestCase):
def run_python(self, code, **kwargs):
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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Library/2019-12-10-21-03-34.bpo-39019.i8RpMZ.rst
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@@ -0,0 +1,2 @@
Implement dummy ``__class_getitem__`` for ``subprocess.Popen``,
``subprocess.CompletedProcess``