Cannot run ctx.run with pty=True on Alpine Linux (musl)

[rajiteh]

I'm trying to run invoke in a docker container with the official python:2.7.13-alpine image and running in to OSError: [Errno 5] I/O error whenever invoke tries to execute an external command using ctx.run(cmd, pty=True).

Running the same task on the debian based image of python 2.7.13 doesn't cause the problem.

Steps to reproduce.

create a dummy tasks.py

from invoke import task

@task
def foo(ctx, pty=False):
  ctx.config.run.shell = '/bin/sh'
  ctx.run("/bin/uname -a", pty=pty)

run the docker container (fails)

 docker run -it --rm -v `pwd`/tasks.py:/tasks.py python:2.7.13-alpine /bin/sh -c "pip install invoke && cd / && invoke foo --pty"

Collecting invoke
  Downloading invoke-0.21.0-py2-none-any.whl (154kB)
    100% |████████████████████████████████| 163kB 1.0MB/s
Installing collected packages: invoke
Successfully installed invoke-0.21.0
Linux 8ed453c901c2 4.9.49-moby #1 SMP Wed Sep 27 23:17:17 UTC 2017 x86_64 Linux
Traceback (most recent call last):
  File "/usr/local/bin/invoke", line 11, in <module>
    sys.exit(program.run())
  File "/usr/local/lib/python2.7/site-packages/invoke/program.py", line 293, in run
    self.execute()
  File "/usr/local/lib/python2.7/site-packages/invoke/program.py", line 414, in execute
    executor.execute(*self.tasks)
  File "/usr/local/lib/python2.7/site-packages/invoke/executor.py", line 129, in execute
    result = call.task(*args, **call.kwargs)
  File "/usr/local/lib/python2.7/site-packages/invoke/tasks.py", line 115, in __call__
    result = self.body(*args, **kwargs)
  File "/tasks.py", line 7, in foo
    ctx.run("/bin/uname -a", pty=pty)
  File "/usr/local/lib/python2.7/site-packages/invoke/context.py", line 82, in run
    return self._run(runner, command, **kwargs)
  File "/usr/local/lib/python2.7/site-packages/invoke/context.py", line 89, in _run
    return runner.run(command, **kwargs)
  File "/usr/local/lib/python2.7/site-packages/invoke/runners.py", line 262, in run
    return self._run_body(command, **kwargs)
  File "/usr/local/lib/python2.7/site-packages/invoke/runners.py", line 356, in _run_body
    raise ThreadException(thread_exceptions)
invoke.exceptions.ThreadException:
Saw 1 exceptions within threads (OSError):


Thread args: {'kwargs': {'buffer_': [u'Linux 8ed453c901c2 4.9.49-moby #1 SMP Wed Sep 27 23:17:17 UTC 2017 x86_64 Linux\r\n'],
            'hide': False,
            'output': <open file '<stdout>', mode 'w' at 0x7f069f8ac150>},
 'target': <bound method Local.handle_stdout of <invoke.runners.Local object at 0x7f069c8b66d0>>}

Traceback (most recent call last):

  File "/usr/local/lib/python2.7/site-packages/invoke/util.py", line 202, in run
    super(ExceptionHandlingThread, self).run()

  File "/usr/local/lib/python2.7/threading.py", line 754, in run
    self.__target(*self.__args, **self.__kwargs)

  File "/usr/local/lib/python2.7/site-packages/invoke/runners.py", line 550, in handle_stdout
    reader=self.read_proc_stdout,

  File "/usr/local/lib/python2.7/site-packages/invoke/runners.py", line 515, in _handle_output
    for data in self.read_proc_output(reader):

  File "/usr/local/lib/python2.7/site-packages/invoke/runners.py", line 490, in read_proc_output
    data = reader(self.read_chunk_size)

  File "/usr/local/lib/python2.7/site-packages/invoke/runners.py", line 916, in read_proc_stdout
    data = os.read(self.parent_fd, num_bytes)

OSError: [Errno 5] I/O error

If pty is disabled, it works.

docker run -it --rm -v `pwd`/tasks.py:/tasks.py python:2.7.13-alpine /bin/sh -c "pip install invoke && cd / && invoke foo"

If used the debian based image, it works regardless.

docker run -it --rm -v `pwd`/tasks.py:/tasks.py python:2.7.13 /bin/sh -c "pip install invoke && cd / && invoke foo --pty"

My guess is that musl compiled python returns different exception string than the gcc one and doesn't get trapped here: https://github.com/pyinvoke/invoke/blob/master/invoke/runners.py#L918-L920

[noirbizarre]

Same issue for me.

Sometimes it's possible to set pty=False but sometimes, the call only works with pty=True :/

[bitprophet]

While I haven't actually reproduced the issue on Alpine itself, @rajiteh is right that this seems to be an issue with the unfortunate string test around IO related OSErrors. (Sob. Y U no additional subclasses, Python?)

I've just pushed a test & patch to master and it'll go out next bugfix. Thanks!