I was playing around with Twisted today and ran into a problem where
Tracebacks aren't emitted on stderr after a deferred callback from a
process called launched by reactor.spawnProcess. The simplified test
case is below. I put "x = y" in the callback function to generate
an exception, y doesn't exist. Uncomment "x = z" right before the
callback and it produces the traceback on stderr just fine.
System is Linux, Python 2.6 and Twisted 8.2.
from twisted.internet import reactor, protocol, defer
import sys
def err(s):
sys.stderr.write(s+'\n')
sys.stderr.flush()
def test():
err('test')
cat = MyPP()
reactor.spawnProcess(cat, "/bin/cat", ["cat", "-"], {})
d = cat.send("Hello world")
d.addCallback(response)
def response(resp):
err('response called')
x = y
err(resp)
class MyPP(protocol.ProcessProtocol):
def __init__(self):
self.defer = defer.Deferred()
def outReceived(self, data):
err("outReceived! with %d bytes" % len(data))
err(" %s" % data)
self.defer.callback(data)
def send(self, c):
self.transport.write("%s\n" % c)
#x = z
return self.defer
if(__name__=='__main__'):
reactor.callWhenRunning(test)
reactor.run()
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