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.
# hgweb/wsgicgi.py - CGI->WSGI translator
#
# Copyright 2006 Eric Hopper <hopper@omnifarious.org>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
#
# This was originally copied from the public domain code at
# http://www.python.org/dev/peps/pep-0333/#the-server-gateway-side
import os
from ..pycompat import getattr
from .. import pycompat
from ..utils import procutil
from . import common
def launch(application):
procutil.setbinary(procutil.stdin)
procutil.setbinary(procutil.stdout)
environ = dict(os.environ.items()) # re-exports
environ.setdefault('PATH_INFO', '')
if environ.get('SERVER_SOFTWARE', '').startswith('Microsoft-IIS'):
# IIS includes script_name in PATH_INFO
scriptname = environ['SCRIPT_NAME']
if environ['PATH_INFO'].startswith(scriptname):
environ['PATH_INFO'] = environ['PATH_INFO'][len(scriptname) :]
stdin = procutil.stdin
if environ.get('HTTP_EXPECT', '').lower() == '100-continue':
stdin = common.continuereader(stdin, procutil.stdout.write)
environ['wsgi.input'] = stdin
environ['wsgi.errors'] = procutil.stderr
environ['wsgi.version'] = (1, 0)
environ['wsgi.multithread'] = False
environ['wsgi.multiprocess'] = True
environ['wsgi.run_once'] = True
if environ.get('HTTPS', 'off').lower() in ('on', '1', 'yes'):
environ['wsgi.url_scheme'] = 'https'
else:
environ['wsgi.url_scheme'] = 'http'
headers_set = []
headers_sent = []
out = procutil.stdout
def write(data):
if not headers_set:
raise AssertionError(b"write() before start_response()")
elif not headers_sent:
# Before the first output, send the stored headers
status, response_headers = headers_sent[:] = headers_set
out.write(b'Status: %s\r\n' % pycompat.bytesurl(status))
for hk, hv in response_headers:
out.write(
b'%s: %s\r\n'
% (pycompat.bytesurl(hk), pycompat.bytesurl(hv))
)
out.write(b'\r\n')
out.write(data)
out.flush()
def start_response(status, response_headers, exc_info=None):
if exc_info:
try:
if headers_sent:
# Re-raise original exception if headers sent
raise exc_info[0](exc_info[1], exc_info[2])
finally:
del exc_info # avoid dangling circular ref
elif headers_set:
raise AssertionError(b"Headers already set!")
headers_set[:] = [status, response_headers]
return write
content = application(environ, start_response)
try:
for chunk in content:
write(chunk)
if not headers_sent:
write(b'') # send headers now if body was empty
finally:
getattr(content, 'close', lambda: None)()