f5e019105e
On POSIX-like systems, calling `subprocess.call()` with both `shell=True` and `executable='...'` has the following behavior: > If `shell=True`, on POSIX the _executable_ argument specifies a > replacement shell for the default `/bin/sh`. (via https://docs.python.org/3/library/subprocess.html?highlight=subprocess#popen-constructor) This seems to have a similar behavior on Windows, but this is problematic when a POSIX shell is substituted for cmd.exe. This is because when `shell=True`, the shell is invoked with a '/c' argument, which is the correct argument for cmd.exe but not for Bash, which expects a '-c' argument instead. See here:1def7754b7/Lib/subprocess.py (L1407)This is problematic when combined with Dotbot's behavior, where the `executable` argument is set based on `$SHELL`. For example, when running in Git Bash, the `$SHELL` environment variable is set to Bash, so any commands run by Dotbot will fail (because it'll invoke Bash with a '/c' argument). This behavior of setting the `executable` argument based on `$SHELL` was introduced in7593d8c134. This is the desired behavior. See discussion in https://github.com/anishathalye/dotbot/issues/97 and https://github.com/anishathalye/dotbot/pull/100. Unfortunately, this doesn't work quite right on Windows. This patch works around the issue by avoiding setting the `executable` argument when the platform is Windows, which is tested using `platform.system() == 'Windows'`. This means that shell commands executed by Dotbot on this platform will always be run using cmd.exe. Invocations of single programs or simple commands will probably work just fine in cmd.exe. If Bash-like behavior is desired, the user will have to write their command as `bash -c '...'`. This shouldn't have any implications for backwards-compatibility, because setting the `executable` argument on Windows didn't do the right thing anyways. Previous workarounds that users had should continue to work with the new code. When using Python from CYGWIN, `platform.system()` returns something like 'CYGWIN_NT-...', so it won't be detected with the check, but this is the correct behavior, because CYGWIN Python's `subprocess.call()` has the POSIX-like behavior. This patch also refactors the code to factor out the `subprocess.call()`, which was being called in both `link.py` and `shell.py`, so the workaround can be applied in a single place. See the following issues/pull requests for a discussion of this bug: - https://github.com/anishathalye/dotbot/issues/170 - https://github.com/anishathalye/dotbot/pull/177 - https://github.com/anishathalye/dotbot/issues/219 An issue has also been raised in Python's issue tracker: - https://bugs.python.org/issue40467 Thanks to @shivapoudel for originally reporting the issue, @SuJiKiNen for debugging it and submitting a pull request, and @mohkale for suggesting factoring out the code so that other plugins could use it.
35 lines
1.4 KiB
Python
35 lines
1.4 KiB
Python
import os
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import subprocess
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import platform
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def shell_command(command, cwd=None, enable_stdin=False, enable_stdout=False, enable_stderr=False):
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with open(os.devnull, 'w') as devnull_w, open(os.devnull, 'r') as devnull_r:
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stdin = None if enable_stdin else devnull_r
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stdout = None if enable_stdout else devnull_w
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stderr = None if enable_stderr else devnull_w
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executable = os.environ.get('SHELL')
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if platform.system() == 'Windows':
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# We avoid setting the executable kwarg on Windows because it does
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# not have the desired effect when combined with shell=True. It
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# will result in the correct program being run (e.g. bash), but it
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# will be invoked with a '/c' argument instead of a '-c' argument,
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# which it won't understand.
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#
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# See https://github.com/anishathalye/dotbot/issues/219 and
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# https://bugs.python.org/issue40467.
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#
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# This means that complex commands that require Bash's parsing
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# won't work; a workaround for this is to write the command as
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# `bash -c "..."`.
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executable = None
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return subprocess.call(
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command,
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shell=True,
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executable=executable,
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stdin=stdin,
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stdout=stdout,
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stderr=stderr,
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cwd=cwd
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)
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