procutil: make stream detection in make_line_buffered more correct and strict
In make_line_buffered(), we don’t want to wrap the stream if we know that lines
get flushed to the underlying raw stream already.
Previously, the heuristic was too optimistic. It assumed that any stream which
is not an instance of io.BufferedIOBase doesn’t need wrapping. However, there
are buffered streams that aren’t instances of io.BufferedIOBase, like
Mercurial’s own winstdout.
The new logic is different in two ways:
First, only for the check, if unwraps any combination of WriteAllWrapper and
winstdout.
Second, it skips wrapping the stream only if it is an instance of io.RawIOBase
(or already wrapped). If it is an instance of io.BufferedIOBase, it gets
wrapped. In any other case, the function raises an exception. This ensures
that, if an unknown stream is passed or we add another wrapper in the future,
we don’t wrap the stream if it’s already line buffered or not wrap the stream
if it’s not line buffered. In fact, this was already helpful during development
of this change. Without it, I possibly would have forgot that WriteAllWrapper
needs to be ignored for the check, leading to unnecessary wrapping if stdout is
unbuffered.
The alternative would have been to always wrap unknown streams. However, I
don’t think that anyone would benefit from being less strict. We can expect
streams from the standard library to be subclassing either io.RawIOBase or
io.BufferedIOBase, so running Mercurial in the standard way should not regress
by this change. Py2exe might replace sys.stdout and sys.stderr, but that
currently breaks Mercurial anyway and also these streams don’t claim to be
interactive, so this function is not called for them.
#!/usr/bin/env python3
#
# Copyright 2018 Gregory Szorc <gregory.szorc@gmail.com>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
import argparse
import pathlib
import shutil
import subprocess
import sys
def get_docker() -> str:
docker = shutil.which('docker.io') or shutil.which('docker')
if not docker:
print('could not find docker executable')
return 1
try:
out = subprocess.check_output([docker, '-h'], stderr=subprocess.STDOUT)
if b'Jansens' in out:
print(
'%s is the Docking System Tray; try installing docker.io'
% docker
)
sys.exit(1)
except subprocess.CalledProcessError as e:
print('error calling `%s -h`: %s' % (docker, e.output))
sys.exit(1)
out = subprocess.check_output([docker, 'version'], stderr=subprocess.STDOUT)
lines = out.splitlines()
if not any(l.startswith((b'Client:', b'Client version:')) for l in lines):
print('`%s version` does not look like Docker' % docker)
sys.exit(1)
if not any(l.startswith((b'Server:', b'Server version:')) for l in lines):
print('`%s version` does not look like Docker' % docker)
sys.exit(1)
return docker
def get_dockerfile(path: pathlib.Path, args: list) -> bytes:
with path.open('rb') as fh:
df = fh.read()
for k, v in args:
df = df.replace(bytes('%%%s%%' % k.decode(), 'utf-8'), v)
return df
def build_docker_image(dockerfile: pathlib.Path, params: list, tag: str):
"""Build a Docker image from a templatized Dockerfile."""
docker = get_docker()
dockerfile_path = pathlib.Path(dockerfile)
dockerfile = get_dockerfile(dockerfile_path, params)
print('building Dockerfile:')
print(dockerfile.decode('utf-8', 'replace'))
args = [
docker,
'build',
'--build-arg',
'http_proxy',
'--build-arg',
'https_proxy',
'--tag',
tag,
'-',
]
print('executing: %r' % args)
p = subprocess.Popen(args, stdin=subprocess.PIPE)
p.communicate(input=dockerfile)
if p.returncode:
raise subprocess.CalledProcessException(
p.returncode,
'failed to build docker image: %s %s' % (p.stdout, p.stderr),
)
def command_build(args):
build_args = []
for arg in args.build_arg:
k, v = arg.split('=', 1)
build_args.append((k.encode('utf-8'), v.encode('utf-8')))
build_docker_image(pathlib.Path(args.dockerfile), build_args, args.tag)
def command_docker(args):
print(get_docker())
def main() -> int:
parser = argparse.ArgumentParser()
subparsers = parser.add_subparsers(title='subcommands')
build = subparsers.add_parser('build', help='Build a Docker image')
build.set_defaults(func=command_build)
build.add_argument(
'--build-arg',
action='append',
default=[],
help='Substitution to perform in Dockerfile; ' 'format: key=value',
)
build.add_argument('dockerfile', help='path to Dockerfile to use')
build.add_argument('tag', help='Tag to apply to created image')
docker = subparsers.add_parser('docker-path', help='Resolve path to Docker')
docker.set_defaults(func=command_docker)
args = parser.parse_args()
return args.func(args)
if __name__ == '__main__':
sys.exit(main())