Re: [Qemu-devel] [PATCH v2] Python3 Support for qmp.py

["Daniel P. Berrange" <berrange@redhat.com>]

On Fri, Jul 07, 2017 at 12:38:47AM +0530, Ishani Chugh wrote:
> This patch intends to make qmp.py compatible with both python2 and python3.
> 
>  * Python 3 does not have dict.has_key(key), use key in dict instead
>  * Avoid line-based I/O since Python 2/3 have different character
>    encoding behavior.  Explicitly encode/decode JSON UTF-8.
>  * Replace print by print function.

If you're going todo this, then you need to actually import the python3
compatible print function - not just call the python2 print statement
with brackets, as the semantics are different:

  $ python2
  >>> print("foo", "bar")
  ('foo', 'bar')
  >>> from __future__ import print_function
  >>> print("foo", "bar")
  foo bar

Only the latter matches python3 semantics

> 
> Signed-off-by: Ishani Chugh <chugh.ishani@research.iiit.ac.in>
> ---
>  scripts/qmp/qmp.py | 58 ++++++++++++++++++++++++++++++++++--------------------
>  1 file changed, 37 insertions(+), 21 deletions(-)
> 
> diff --git a/scripts/qmp/qmp.py b/scripts/qmp/qmp.py
> index 62d3651..58fb7d1 100644
> --- a/scripts/qmp/qmp.py
> +++ b/scripts/qmp/qmp.py
> @@ -42,6 +42,7 @@ class QEMUMonitorProtocol:
>          self.__address = address
>          self._debug = debug
>          self.__sock = self.__get_sock()
> +        self.__data = b""
>          if server:
>              self.__sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
>              self.__sock.bind(self.__address)
> @@ -56,7 +57,7 @@ class QEMUMonitorProtocol:
>  
>      def __negotiate_capabilities(self):
>          greeting = self.__json_read()
> -        if greeting is None or not greeting.has_key('QMP'):
> +        if greeting is None or 'QMP' not in greeting:
>              raise QMPConnectError
>          # Greeting seems ok, negotiate capabilities
>          resp = self.cmd('qmp_capabilities')
> @@ -64,15 +65,28 @@ class QEMUMonitorProtocol:
>              return greeting
>          raise QMPCapabilitiesError
>  
> +    def __sock_readline(self):
> +        while True:
> +            ch = self.__sock.recv(1)
> +            if ch is None:
> +                if self.__data:
> +                    raise ValueError('socket closed mid-line')
> +                return None
> +            self.__data += ch
> +            if ch == b'\n':
> +                line = self.__data.decode('utf-8')
> +                self.__data = b""
> +                return line
> +
>      def __json_read(self, only_event=False):
>          while True:
> -            data = self.__sockfile.readline()
> +            data = self.__sock_readline()

So originally we could get back a "str" on python2, but now
we get a "str" (which is unicode) on python2, but "unicode"
on python2.

>              if not data:
>                  return
>              resp = json.loads(data)

This means the 'resp' now contains "unicode" data too on
python2 instead of 'str'.

This hopefully isn't a problem, but we certainly need to
make sure the iotests still pass on py2, as it could well
have a ripple effect in this respect.  Have you run the
iotests with this change applied ?

>              if 'event' in resp:
>                  if self._debug:
> -                    print >>sys.stderr, "QMP:<<< %s" % resp
> +                    print("QMP:<<< %s" % resp)

This is changing from printing to stderr, to printing to stdout
which is not desirable. Likewise all the similar changes below.

>                  self.__events.append(resp)
>                  if not only_event:
>                      continue
> @@ -87,10 +101,10 @@ class QEMUMonitorProtocol:
>          @param wait (bool): block until an event is available.
>          @param wait (float): If wait is a float, treat it as a timeout value.
>  
> -        @raise QMPTimeoutError: If a timeout float is provided and the timeout
> -                                period elapses.
> -        @raise QMPConnectError: If wait is True but no events could be retrieved
> -                                or if some other error occurred.
> +        @raise QMPTimeoutError: If a timeout float is provided and the
> +                                timeout period elapses.
> +        @raise QMPConnectError: If wait is True but no events could be
> +                                retrieved or if some other error occurred.
>          """

Don't mix whitespace changes in with other functional changes.


>  
>          # Check for new events regardless and pull them into the cache:
> @@ -98,9 +112,11 @@ class QEMUMonitorProtocol:
>          try:
>              self.__json_read()
>          except socket.error as err:
> -            if err[0] == errno.EAGAIN:
> +            if err.errno == errno.EAGAIN:
>                  # No data available
>                  pass
> +            else:
> +                raise
>          self.__sock.setblocking(1)
>  
>          # Wait for new events, if needed.
> @@ -128,7 +144,6 @@ class QEMUMonitorProtocol:
>          @raise QMPCapabilitiesError if fails to negotiate capabilities
>          """
>          self.__sock.connect(self.__address)
> -        self.__sockfile = self.__sock.makefile()
>          if negotiate:
>              return self.__negotiate_capabilities()
>  
> @@ -143,7 +158,6 @@ class QEMUMonitorProtocol:
>          """
>          self.__sock.settimeout(15)
>          self.__sock, _ = self.__sock.accept()
> -        self.__sockfile = self.__sock.makefile()
>          return self.__negotiate_capabilities()
>  
>      def cmd_obj(self, qmp_cmd):
> @@ -155,16 +169,17 @@ class QEMUMonitorProtocol:
>                  been closed
>          """
>          if self._debug:
> -            print >>sys.stderr, "QMP:>>> %s" % qmp_cmd
> +            print("QMP:>>> %s" % qmp_cmd)
>          try:
> -            self.__sock.sendall(json.dumps(qmp_cmd))
> +            command = json.dumps(qmp_cmd)
> +            self.__sock.sendall(command.encode('UTF-8'))
>          except socket.error as err:
> -            if err[0] == errno.EPIPE:
> +            if err.errno == errno.EPIPE:
>                  return
> -            raise socket.error(err)
> +            raise
>          resp = self.__json_read()
>          if self._debug:
> -            print >>sys.stderr, "QMP:<<< %s" % resp
> +            print("QMP:<<< %s" % resp)
>          return resp
>  
>      def cmd(self, name, args=None, id=None):
> @@ -175,7 +190,7 @@ class QEMUMonitorProtocol:
>          @param args: command arguments (dict)
>          @param id: command id (dict, list, string or int)
>          """
> -        qmp_cmd = { 'execute': name }
> +        qmp_cmd = {'execute': name}

Again bogus whitespace changes

>          if args:
>              qmp_cmd['arguments'] = args
>          if id:
> @@ -184,7 +199,7 @@ class QEMUMonitorProtocol:
>  
>      def command(self, cmd, **kwds):
>          ret = self.cmd(cmd, kwds)
> -        if ret.has_key('error'):
> +        if 'error' in ret:
>              raise Exception(ret['error']['desc'])
>          return ret['return']
>  
> @@ -197,8 +212,8 @@ class QEMUMonitorProtocol:
>  
>          @raise QMPTimeoutError: If a timeout float is provided and the timeout
>                                  period elapses.
> -        @raise QMPConnectError: If wait is True but no events could be retrieved
> -                                or if some other error occurred.
> +        @raise QMPConnectError: If wait is True but no events could be
> +                                retrieved or if some other error occurred.

And again

>  
>          @return The first available QMP event, or None.
>          """
> @@ -217,8 +232,8 @@ class QEMUMonitorProtocol:
>  
>          @raise QMPTimeoutError: If a timeout float is provided and the timeout
>                                  period elapses.
> -        @raise QMPConnectError: If wait is True but no events could be retrieved
> -                                or if some other error occurred.
> +        @raise QMPConnectError: If wait is True but no events could be
> +                                retrieved or if some other error occurred.

Same

>  
>          @return The list of available QMP events.
>          """
> @@ -245,3 +260,4 @@ class QEMUMonitorProtocol:
>  
>      def is_scm_available(self):
>          return self.__sock.family == socket.AF_UNIX
> +

Adding trailing blank line to the file is bad.

Regards,
Daniel
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