__init__.py 4.71 KB
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#!/usr/bin/env python
#
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# __init__.py - Miscellaneous functions used throughout fsl_ci.
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#
# Author: Paul McCarthy <pauldmccarthy@gmail.com>
#


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import os.path    as op
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import               os
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import               sys
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import               errno
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import               shlex
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import               time
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import               tempfile
import contextlib as ctxlib
import subprocess as sp

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import yaml
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__version__ = '0.9.0'
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"""Current version of the fsl-ci-rules."""


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USERNAME = 'fsl-ci-rules'
"""Username to be used for all git interactions which require one. """


EMAIL = 'fsl-ci-rules@git.fmrib.ox.ac.uk'
"""Password to be used for all git interactions which require one. """


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def fprint(*args, **kwargs):
    """Print with flush=True. """
    print(*args, **kwargs, flush=True)


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@ctxlib.contextmanager
def tempdir():
    """Context manager to create, and change into, a temporary directory, and
    then afterwards delete it and change back to the original working
    directory.
    """
    with tempfile.TemporaryDirectory() as td:
        prevdir = os.getcwd()
        os.chdir(td)
        try:
            yield td
        finally:
            os.chdir(prevdir)


@ctxlib.contextmanager
def indir(dirname):
    """Context manager to change into a directory, and then afterwards
    change back to the original working directory.
    """
    prevdir = os.getcwd()
    os.chdir(dirname)
    try:
        yield
    finally:
        os.chdir(prevdir)


def sprun(cmd, **kwargs):
    """Runs the given command with subprocess.run. """
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    fprint(f'Running {cmd}')
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    if not kwargs.get('shell', False):
        cmd = shlex.split(cmd)
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    # we set stdout/stderr for compatibility
    # with CaptureStdout (see below)
    if 'check'  not in kwargs: kwargs['check']  = True
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    if 'capture_output' not in kwargs:
        if 'stdout' not in kwargs: kwargs['stdout'] = sys.stdout
        if 'stderr' not in kwargs: kwargs['stderr'] = sys.stderr
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    return sp.run(cmd, **kwargs)
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def spcap(cmd, **kwargs):
    """Call sprun(..., capture_output=True), and return stdout as a string. """
    return sprun(cmd, capture_output=True, **kwargs).stdout.decode()


def which(command):
    """Run "which command". """
    return spcap(f'which {command}').strip()


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@ctxlib.contextmanager
def lockdir(dirname):
    """Primitive mechanism by which concurrent access to a directory can be
    prevented. Attempts to create a semaphore file in the directory, but waits
    if that file already exists. Removes the file when finished.
    """

    delay    = 10
    lockfile = op.join(dirname, '.fsl_ci.lockdir')

    while True:
        try:
            fprint(f'Attempting to lock {dirname} for exclusive access.')
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            fd = os.open(lockfile, os.O_CREAT | os.O_EXCL | os.O_RDWR)
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            break
        except OSError as e:
            if e.errno != errno.EEXIST:
                raise e
            fprint(f'{dirname} is already locked - '
                   f'trying again in {delay} seconds ...')
        time.sleep(10)

    fprint(f'Exclusive access acquired for {dirname} ...')
    try:
        yield

    finally:
        fprint(f'Relinquishing lock on {dirname}')
        os.close( fd)
        os.unlink(lockfile)
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def loadyaml(s):
    """Loads a YAML string, returning a dict-like. """
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    return yaml.load(s, Loader=yaml.Loader)
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def dumpyaml(o):
    """Dumps the given YAML to a string. """
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    return yaml.dump(o, sort_keys=False)
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class CaptureStdout:
    """Context manager which captures stdout and stderr. """

    def __init__(self):
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        self.tmpdir        = tempfile.TemporaryDirectory()
        self.__mock_stdout = open(op.join(self.tmpdir.name, 'stdout'), 'wt')
        self.__mock_stderr = open(op.join(self.tmpdir.name, 'stderr'), 'wt')
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    def __enter__(self):
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        if self.tmpdir is None:
            raise RuntimeError('CaptureStdout can only be used once')

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        self.__real_stdout = sys.stdout
        self.__real_stderr = sys.stderr
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        sys.stdout         = self.__mock_stdout
        sys.stderr         = self.__mock_stderr
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        return self
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    def __exit__(self, *args, **kwargs):
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        sys.stdout = self.__real_stdout
        sys.stderr = self.__real_stderr

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        self.__mock_stdout.close()
        self.__mock_stderr.close()

        with open(self.__mock_stdout.name, 'rt') as f:
            self.__mock_stdout = f.read()
        with open(self.__mock_stderr.name, 'rt') as f:
            self.__mock_stderr = f.read()

        self.tmpdir.cleanup()
        self.tmpdir = None

    @property
    def real_stdout(self):
        return self.__real_stdout

    @property
    def real_stderr(self):
        return self.__real_stderr

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    @property
    def stdout(self):
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        return self.__mock_stdout
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    @property
    def stderr(self):
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        return self.__mock_stderr