Viewing file:  context.py (5.29 KB) -rw-r--r--
Select action/file-type:
 (+) |  (+) |  (+) | Code (+) | Session (+) |  (+) | SDB (+) |  (+) |  (+) |  (+) |  (+) |  (+) |
import os
import subprocess
import contextlib
import functools
import tempfile
import shutil
import operator
@contextlib.contextmanager
def pushd(dir):
orig = os.getcwd()
os.chdir(dir)
try:
yield dir
finally:
os.chdir(orig)
@contextlib.contextmanager
def tarball_context(url, target_dir=None, runner=None, pushd=pushd):
"""
Get a tarball, extract it, change to that directory, yield, then
clean up.
`runner` is the function to invoke commands.
`pushd` is a context manager for changing the directory.
"""
if target_dir is None:
target_dir = os.path.basename(url).replace('.tar.gz', '').replace('.tgz', '')
if runner is None:
runner = functools.partial(subprocess.check_call, shell=True)
# In the tar command, use --strip-components=1 to strip the first path and
# then
# use -C to cause the files to be extracted to {target_dir}. This ensures
# that we always know where the files were extracted.
runner('mkdir {target_dir}'.format(**vars()))
try:
getter = 'wget {url} -O -'
extract = 'tar x{compression} --strip-components=1 -C {target_dir}'
cmd = ' | '.join((getter, extract))
runner(cmd.format(compression=infer_compression(url), **vars()))
with pushd(target_dir):
yield target_dir
finally:
runner('rm -Rf {target_dir}'.format(**vars()))
def infer_compression(url):
"""
Given a URL or filename, infer the compression code for tar.
"""
# cheat and just assume it's the last two characters
compression_indicator = url[-2:]
mapping = dict(gz='z', bz='j', xz='J')
# Assume 'z' (gzip) if no match
return mapping.get(compression_indicator, 'z')
@contextlib.contextmanager
def temp_dir(remover=shutil.rmtree):
"""
Create a temporary directory context. Pass a custom remover
to override the removal behavior.
"""
temp_dir = tempfile.mkdtemp()
try:
yield temp_dir
finally:
remover(temp_dir)
@contextlib.contextmanager
def repo_context(url, branch=None, quiet=True, dest_ctx=temp_dir):
"""
Check out the repo indicated by url.
If dest_ctx is supplied, it should be a context manager
to yield the target directory for the check out.
"""
exe = 'git' if 'git' in url else 'hg'
with dest_ctx() as repo_dir:
cmd = [exe, 'clone', url, repo_dir]
if branch:
cmd.extend(['--branch', branch])
devnull = open(os.path.devnull, 'w')
stdout = devnull if quiet else None
subprocess.check_call(cmd, stdout=stdout)
yield repo_dir
@contextlib.contextmanager
def null():
yield
class ExceptionTrap:
"""
A context manager that will catch certain exceptions and provide an
indication they occurred.
>>> with ExceptionTrap() as trap:
... raise Exception()
>>> bool(trap)
True
>>> with ExceptionTrap() as trap:
... pass
>>> bool(trap)
False
>>> with ExceptionTrap(ValueError) as trap:
... raise ValueError("1 + 1 is not 3")
>>> bool(trap)
True
>>> with ExceptionTrap(ValueError) as trap:
... raise Exception()
Traceback (most recent call last):
...
Exception
>>> bool(trap)
False
"""
exc_info = None, None, None
def __init__(self, exceptions=(Exception,)):
self.exceptions = exceptions
def __enter__(self):
return self
@property
def type(self):
return self.exc_info[0]
@property
def value(self):
return self.exc_info[1]
@property
def tb(self):
return self.exc_info[2]
def __exit__(self, *exc_info):
type = exc_info[0]
matches = type and issubclass(type, self.exceptions)
if matches:
self.exc_info = exc_info
return matches
def __bool__(self):
return bool(self.type)
def raises(self, func, *, _test=bool):
"""
Wrap func and replace the result with the truth
value of the trap (True if an exception occurred).
First, give the decorator an alias to support Python 3.8
Syntax.
>>> raises = ExceptionTrap(ValueError).raises
Now decorate a function that always fails.
>>> @raises
... def fail():
... raise ValueError('failed')
>>> fail()
True
"""
@functools.wraps(func)
def wrapper(*args, **kwargs):
with ExceptionTrap(self.exceptions) as trap:
func(*args, **kwargs)
return _test(trap)
return wrapper
def passes(self, func):
"""
Wrap func and replace the result with the truth
value of the trap (True if no exception).
First, give the decorator an alias to support Python 3.8
Syntax.
>>> passes = ExceptionTrap(ValueError).passes
Now decorate a function that always fails.
>>> @passes
... def fail():
... raise ValueError('failed')
>>> fail()
False
"""
return self.raises(func, _test=operator.not_)
class suppress(contextlib.suppress, contextlib.ContextDecorator):
"""
A version of contextlib.suppress with decorator support.
>>> @suppress(KeyError)
... def key_error():
... {}['']
>>> key_error()
"""
|