bpo-42388: Fix subprocess.check_output input=None when text=True (GH-23467)
When the modern text= spelling of the universal_newlines= parameter was added
for Python 3.7, check_output's special case around input=None was overlooked.
So it behaved differently with universal_newlines=True vs text=True. This
reconciles the behavior to be consistent and adds a test to guarantee it.
Also clarifies the existing check_output documentation.
Co-authored-by: Alexey Izbyshev <izbyshev@ispras.ru>
(cherry picked from commit 64abf37344
)
Co-authored-by: Gregory P. Smith <greg@krypto.org>
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@ -1127,8 +1127,9 @@ calls these functions.
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The arguments shown above are merely some common ones.
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The full function signature is largely the same as that of :func:`run` -
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most arguments are passed directly through to that interface.
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However, explicitly passing ``input=None`` to inherit the parent's
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standard input file handle is not supported.
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One API deviation from :func:`run` behavior exists: passing ``input=None``
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will behave the same as ``input=b''`` (or ``input=''``, depending on other
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arguments) rather than using the parent's standard input file handle.
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By default, this function will return the data as encoded bytes. The actual
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encoding of the output data may depend on the command being invoked, so the
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@ -406,7 +406,11 @@ def check_output(*popenargs, timeout=None, **kwargs):
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if 'input' in kwargs and kwargs['input'] is None:
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# Explicitly passing input=None was previously equivalent to passing an
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# empty string. That is maintained here for backwards compatibility.
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kwargs['input'] = '' if kwargs.get('universal_newlines', False) else b''
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if kwargs.get('universal_newlines') or kwargs.get('text'):
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empty = ''
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else:
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empty = b''
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kwargs['input'] = empty
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return run(*popenargs, stdout=PIPE, timeout=timeout, check=True,
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**kwargs).stdout
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@ -195,6 +195,28 @@ class ProcessTestCase(BaseTestCase):
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input=b'pear')
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self.assertIn(b'PEAR', output)
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def test_check_output_input_none(self):
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"""input=None has a legacy meaning of input='' on check_output."""
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output = subprocess.check_output(
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[sys.executable, "-c",
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"import sys; print('XX' if sys.stdin.read() else '')"],
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input=None)
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self.assertNotIn(b'XX', output)
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def test_check_output_input_none_text(self):
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output = subprocess.check_output(
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[sys.executable, "-c",
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"import sys; print('XX' if sys.stdin.read() else '')"],
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input=None, text=True)
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self.assertNotIn('XX', output)
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def test_check_output_input_none_universal_newlines(self):
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output = subprocess.check_output(
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[sys.executable, "-c",
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"import sys; print('XX' if sys.stdin.read() else '')"],
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input=None, universal_newlines=True)
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self.assertNotIn('XX', output)
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def test_check_output_stdout_arg(self):
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# check_output() refuses to accept 'stdout' argument
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with self.assertRaises(ValueError) as c:
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@ -0,0 +1,2 @@
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Fix subprocess.check_output(..., input=None) behavior when text=True to be
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consistent with that of the documentation and universal_newlines=True.
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