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.
import sys
from mercurial import (
error,
pycompat,
ui as uimod,
util,
wireprototypes,
wireprotov1peer,
wireprotov1server,
)
from mercurial.utils import stringutil
stringio = util.stringio
class proto:
def __init__(self, args):
self.args = args
self.name = 'dummyproto'
def getargs(self, spec):
args = self.args
args.setdefault(b'*', {})
names = spec.split()
return [args[n] for n in names]
def checkperm(self, perm):
pass
wireprototypes.TRANSPORTS['dummyproto'] = {
'transport': 'dummy',
'version': 1,
}
class clientpeer(wireprotov1peer.wirepeer):
def __init__(self, serverrepo, ui):
self.serverrepo = serverrepo
self.ui = ui
def url(self):
return b'test'
def local(self):
return None
def peer(self):
return self
def canpush(self):
return True
def close(self):
pass
def capabilities(self):
return [b'batch']
def _call(self, cmd, **args):
args = pycompat.byteskwargs(args)
res = wireprotov1server.dispatch(self.serverrepo, proto(args), cmd)
if isinstance(res, wireprototypes.bytesresponse):
return res.data
elif isinstance(res, bytes):
return res
else:
raise error.Abort('dummy client does not support response type')
def _callstream(self, cmd, **args):
return stringio(self._call(cmd, **args))
@wireprotov1peer.batchable
def greet(self, name):
return {b'name': mangle(name)}, unmangle
class serverrepo:
def __init__(self, ui):
self.ui = ui
def greet(self, name):
return b"Hello, " + name
def filtered(self, name):
return self
def mangle(s):
return b''.join(pycompat.bytechr(ord(c) + 1) for c in pycompat.bytestr(s))
def unmangle(s):
return b''.join(pycompat.bytechr(ord(c) - 1) for c in pycompat.bytestr(s))
def greet(repo, proto, name):
return mangle(repo.greet(unmangle(name)))
wireprotov1server.commands[b'greet'] = (greet, b'name')
srv = serverrepo(uimod.ui())
clt = clientpeer(srv, uimod.ui())
def printb(data, end=b'\n'):
out = getattr(sys.stdout, 'buffer', sys.stdout)
out.write(data + end)
out.flush()
printb(clt.greet(b"Foobar"))
with clt.commandexecutor() as e:
fgreet1 = e.callcommand(b'greet', {b'name': b'Fo, =;:<o'})
fgreet2 = e.callcommand(b'greet', {b'name': b'Bar'})
printb(
stringutil.pprint([f.result() for f in (fgreet1, fgreet2)], bprefix=True)
)