tests/test-wireproto-clientreactor.py

internals: document CBOR utilization

I spoke with some people at Mozilla about CBOR and they advised me
that we should be careful about the subset of CBOR we use in order
to mitigate security, performance, and compatibility concerns.

This commit establishes a document that attempts to formalize our
use of CBOR.

Its main limitations are on what types are allowed. It explicitly
enumerates which types are supported. Notable missing features
include:

* Indefinite-length arrays and maps
* Text strings (bytes all the way)
* Floats
* Date/time types
* Big integers
* Use of indefinite-length byte strings for map keys, values in
  containers.

If we have a need for any of these, we can have a discussion about
them when the time comes.

Differential Revision: https://phab.mercurial-scm.org/D4412

from __future__ import absolute_import

import unittest

from mercurial import (
    error,
    wireprotoframing as framing,
)

ffs = framing.makeframefromhumanstring

def sendframe(reactor, frame):
    """Send a frame bytearray to a reactor."""
    header = framing.parseheader(frame)
    payload = frame[framing.FRAME_HEADER_SIZE:]
    assert len(payload) == header.length

    return reactor.onframerecv(framing.frame(header.requestid,
                                             header.streamid,
                                             header.streamflags,
                                             header.typeid,
                                             header.flags,
                                             payload))

class SingleSendTests(unittest.TestCase):
    """A reactor that can only send once rejects subsequent sends."""

    if not getattr(unittest.TestCase, 'assertRaisesRegex', False):
        # Python 3.7 deprecates the regex*p* version, but 2.7 lacks
        # the regex version.
        assertRaisesRegex = (# camelcase-required
            unittest.TestCase.assertRaisesRegexp)

    def testbasic(self):
        reactor = framing.clientreactor(hasmultiplesend=False, buffersends=True)

        request, action, meta = reactor.callcommand(b'foo', {})
        self.assertEqual(request.state, b'pending')
        self.assertEqual(action, b'noop')

        action, meta = reactor.flushcommands()
        self.assertEqual(action, b'sendframes')

        for frame in meta[b'framegen']:
            self.assertEqual(request.state, b'sending')

        self.assertEqual(request.state, b'sent')

        with self.assertRaisesRegex(error.ProgrammingError,
                                     'cannot issue new commands'):
            reactor.callcommand(b'foo', {})

        with self.assertRaisesRegex(error.ProgrammingError,
                                     'cannot issue new commands'):
            reactor.callcommand(b'foo', {})

class NoBufferTests(unittest.TestCase):
    """A reactor without send buffering sends requests immediately."""
    def testbasic(self):
        reactor = framing.clientreactor(hasmultiplesend=True, buffersends=False)

        request, action, meta = reactor.callcommand(b'command1', {})
        self.assertEqual(request.requestid, 1)
        self.assertEqual(action, b'sendframes')

        self.assertEqual(request.state, b'pending')

        for frame in meta[b'framegen']:
            self.assertEqual(request.state, b'sending')

        self.assertEqual(request.state, b'sent')

        action, meta = reactor.flushcommands()
        self.assertEqual(action, b'noop')

        # And we can send another command.
        request, action, meta = reactor.callcommand(b'command2', {})
        self.assertEqual(request.requestid, 3)
        self.assertEqual(action, b'sendframes')

        for frame in meta[b'framegen']:
            self.assertEqual(request.state, b'sending')

        self.assertEqual(request.state, b'sent')

class BadFrameRecvTests(unittest.TestCase):
    if not getattr(unittest.TestCase, 'assertRaisesRegex', False):
        # Python 3.7 deprecates the regex*p* version, but 2.7 lacks
        # the regex version.
        assertRaisesRegex = (# camelcase-required
            unittest.TestCase.assertRaisesRegexp)

    def testoddstream(self):
        reactor = framing.clientreactor()

        action, meta = sendframe(reactor, ffs(b'1 1 0 1 0 foo'))
        self.assertEqual(action, b'error')
        self.assertEqual(meta[b'message'],
                         b'received frame with odd numbered stream ID: 1')

    def testunknownstream(self):
        reactor = framing.clientreactor()

        action, meta = sendframe(reactor, ffs(b'1 0 0 1 0 foo'))
        self.assertEqual(action, b'error')
        self.assertEqual(meta[b'message'],
                         b'received frame on unknown stream without beginning '
                         b'of stream flag set')

    def testunhandledframetype(self):
        reactor = framing.clientreactor(buffersends=False)

        request, action, meta = reactor.callcommand(b'foo', {})
        for frame in meta[b'framegen']:
            pass

        with self.assertRaisesRegex(error.ProgrammingError,
                                     'unhandled frame type'):
            sendframe(reactor, ffs(b'1 0 stream-begin text-output 0 foo'))

class StreamTests(unittest.TestCase):
    def testmultipleresponseframes(self):
        reactor = framing.clientreactor(buffersends=False)

        request, action, meta = reactor.callcommand(b'foo', {})

        self.assertEqual(action, b'sendframes')
        for f in meta[b'framegen']:
            pass

        action, meta = sendframe(
            reactor,
            ffs(b'%d 0 stream-begin command-response 0 foo' %
                request.requestid))
        self.assertEqual(action, b'responsedata')

        action, meta = sendframe(
            reactor,
            ffs(b'%d 0 0 command-response eos bar' % request.requestid))
        self.assertEqual(action, b'responsedata')

if __name__ == '__main__':
    import silenttestrunner
    silenttestrunner.main(__name__)