httppeer: document why super() isn't used

Adding a follow-up to document lack of super() per Augie's
request.

mercurial/httppeer.py

@@ -1,317 +1,320 b''
 # httppeer.py - HTTP repository proxy classes for mercurial
 #
 # Copyright 2005, 2006 Matt Mackall <[e-mail]>
 # Copyright 2006 Vadim Gelfer <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 from __future__ import absolute_import
 
 import errno
 import os
 import socket
 import tempfile
 
 from .i18n import _
 from .node import nullid
 from . import (
     bundle2,
     error,
     httpconnection,
     statichttprepo,
     url,
     util,
     wireproto,
 )
 
 httplib = util.httplib
 urlerr = util.urlerr
 urlreq = util.urlreq
 
 # FUTURE: consider refactoring this API to use generators. This will
 # require a compression engine API to emit generators.
 def decompressresponse(response, engine):
     try:
         reader = engine.decompressorreader(response)
     except httplib.HTTPException:
         raise IOError(None, _('connection ended unexpectedly'))
 
     # We need to wrap reader.read() so HTTPException on subsequent
     # reads is also converted.
+    # Ideally we'd use super() here. However, if ``reader`` isn't a new-style
+    # class, this can raise:
+    # TypeError: super() argument 1 must be type, not classobj
     origread = reader.read
     class readerproxy(reader.__class__):
         def read(self, *args, **kwargs):
             try:
                 return origread(*args, **kwargs)
             except httplib.HTTPException:
                 raise IOError(None, _('connection ended unexpectedly'))
 
     reader.__class__ = readerproxy
     return reader
 
 class httppeer(wireproto.wirepeer):
     def __init__(self, ui, path):
         self.path = path
         self.caps = None
         self.handler = None
         self.urlopener = None
         self.requestbuilder = None
         u = util.url(path)
         if u.query or u.fragment:
             raise error.Abort(_('unsupported URL component: "%s"') %
                              (u.query or u.fragment))
 
         # urllib cannot handle URLs with embedded user or passwd
         self._url, authinfo = u.authinfo()
 
         self.ui = ui
         self.ui.debug('using %s\n' % self._url)
 
         self.urlopener = url.opener(ui, authinfo)
         self.requestbuilder = urlreq.request
 
     def __del__(self):
         urlopener = getattr(self, 'urlopener', None)
         if urlopener:
             for h in urlopener.handlers:
                 h.close()
                 getattr(h, "close_all", lambda : None)()
 
     def url(self):
         return self.path
 
     # look up capabilities only when needed
 
     def _fetchcaps(self):
         self.caps = set(self._call('capabilities').split())
 
     def _capabilities(self):
         if self.caps is None:
             try:
                 self._fetchcaps()
             except error.RepoError:
                 self.caps = set()
             self.ui.debug('capabilities: %s\n' %
                           (' '.join(self.caps or ['none'])))
         return self.caps
 
     def lock(self):
         raise error.Abort(_('operation not supported over http'))
 
     def _callstream(self, cmd, _compressible=False, **args):
         if cmd == 'pushkey':
             args['data'] = ''
         data = args.pop('data', None)
         headers = args.pop('headers', {})
 
         self.ui.debug("sending %s command\n" % cmd)
         q = [('cmd', cmd)]
         headersize = 0
         # Important: don't use self.capable() here or else you end up
         # with infinite recursion when trying to look up capabilities
         # for the first time.
         postargsok = self.caps is not None and 'httppostargs' in self.caps
         # TODO: support for httppostargs when data is a file-like
         # object rather than a basestring
         canmungedata = not data or isinstance(data, basestring)
         if postargsok and canmungedata:
             strargs = urlreq.urlencode(sorted(args.items()))
             if strargs:
                 if not data:
                     data = strargs
                 elif isinstance(data, basestring):
                     data = strargs + data
                 headers['X-HgArgs-Post'] = len(strargs)
         else:
             if len(args) > 0:
                 httpheader = self.capable('httpheader')
                 if httpheader:
                     headersize = int(httpheader.split(',', 1)[0])
             if headersize > 0:
                 # The headers can typically carry more data than the URL.
                 encargs = urlreq.urlencode(sorted(args.items()))
                 headerfmt = 'X-HgArg-%s'
                 contentlen = headersize - len(headerfmt % '000' + ': \r\n')
                 headernum = 0
                 varyheaders = []
                 for i in xrange(0, len(encargs), contentlen):
                     headernum += 1
                     header = headerfmt % str(headernum)
                     headers[header] = encargs[i:i + contentlen]
                     varyheaders.append(header)
                 headers['Vary'] = ','.join(varyheaders)
             else:
                 q += sorted(args.items())
         qs = '?%s' % urlreq.urlencode(q)
         cu = "%s%s" % (self._url, qs)
         size = 0
         if util.safehasattr(data, 'length'):
             size = data.length
         elif data is not None:
             size = len(data)
         if size and self.ui.configbool('ui', 'usehttp2', False):
             headers['Expect'] = '100-Continue'
             headers['X-HgHttp2'] = '1'
         if data is not None and 'Content-Type' not in headers:
             headers['Content-Type'] = 'application/mercurial-0.1'
         req = self.requestbuilder(cu, data, headers)
         if data is not None:
             self.ui.debug("sending %s bytes\n" % size)
             req.add_unredirected_header('Content-Length', '%d' % size)
         try:
             resp = self.urlopener.open(req)
         except urlerr.httperror as inst:
             if inst.code == 401:
                 raise error.Abort(_('authorization failed'))
             raise
         except httplib.HTTPException as inst:
             self.ui.debug('http error while sending %s command\n' % cmd)
             self.ui.traceback()
             raise IOError(None, inst)
         # record the url we got redirected to
         resp_url = resp.geturl()
         if resp_url.endswith(qs):
             resp_url = resp_url[:-len(qs)]
         if self._url.rstrip('/') != resp_url.rstrip('/'):
             if not self.ui.quiet:
                 self.ui.warn(_('real URL is %s\n') % resp_url)
         self._url = resp_url
         try:
             proto = resp.getheader('content-type')
         except AttributeError:
             proto = resp.headers.get('content-type', '')
 
         safeurl = util.hidepassword(self._url)
         if proto.startswith('application/hg-error'):
             raise error.OutOfBandError(resp.read())
         # accept old "text/plain" and "application/hg-changegroup" for now
         if not (proto.startswith('application/mercurial-') or
                 (proto.startswith('text/plain')
                  and not resp.headers.get('content-length')) or
                 proto.startswith('application/hg-changegroup')):
             self.ui.debug("requested URL: '%s'\n" % util.hidepassword(cu))
             raise error.RepoError(
                 _("'%s' does not appear to be an hg repository:\n"
                   "---%%<--- (%s)\n%s\n---%%<---\n")
                 % (safeurl, proto or 'no content-type', resp.read(1024)))
 
         if proto.startswith('application/mercurial-'):
             try:
                 version = proto.split('-', 1)[1]
                 version_info = tuple([int(n) for n in version.split('.')])
             except ValueError:
                 raise error.RepoError(_("'%s' sent a broken Content-Type "
                                         "header (%s)") % (safeurl, proto))
             if version_info > (0, 1):
                 raise error.RepoError(_("'%s' uses newer protocol %s") %
                                       (safeurl, version))
 
         if _compressible:
             return decompressresponse(resp, util.compengines['zlib'])
 
         return resp
 
     def _call(self, cmd, **args):
         fp = self._callstream(cmd, **args)
         try:
             return fp.read()
         finally:
             # if using keepalive, allow connection to be reused
             fp.close()
 
     def _callpush(self, cmd, cg, **args):
         # have to stream bundle to a temp file because we do not have
         # http 1.1 chunked transfer.
 
         types = self.capable('unbundle')
         try:
             types = types.split(',')
         except AttributeError:
             # servers older than d1b16a746db6 will send 'unbundle' as a
             # boolean capability. They only support headerless/uncompressed
             # bundles.
             types = [""]
         for x in types:
             if x in bundle2.bundletypes:
                 type = x
                 break
 
         tempname = bundle2.writebundle(self.ui, cg, None, type)
         fp = httpconnection.httpsendfile(self.ui, tempname, "rb")
         headers = {'Content-Type': 'application/mercurial-0.1'}
 
         try:
             r = self._call(cmd, data=fp, headers=headers, **args)
             vals = r.split('\n', 1)
             if len(vals) < 2:
                 raise error.ResponseError(_("unexpected response:"), r)
             return vals
         except socket.error as err:
             if err.args[0] in (errno.ECONNRESET, errno.EPIPE):
                 raise error.Abort(_('push failed: %s') % err.args[1])
             raise error.Abort(err.args[1])
         finally:
             fp.close()
             os.unlink(tempname)
 
     def _calltwowaystream(self, cmd, fp, **args):
         fh = None
         fp_ = None
         filename = None
         try:
             # dump bundle to disk
             fd, filename = tempfile.mkstemp(prefix="hg-bundle-", suffix=".hg")
             fh = os.fdopen(fd, "wb")
             d = fp.read(4096)
             while d:
                 fh.write(d)
                 d = fp.read(4096)
             fh.close()
             # start http push
             fp_ = httpconnection.httpsendfile(self.ui, filename, "rb")
             headers = {'Content-Type': 'application/mercurial-0.1'}
             return self._callstream(cmd, data=fp_, headers=headers, **args)
         finally:
             if fp_ is not None:
                 fp_.close()
             if fh is not None:
                 fh.close()
                 os.unlink(filename)
 
     def _callcompressable(self, cmd, **args):
         return self._callstream(cmd, _compressible=True, **args)
 
     def _abort(self, exception):
         raise exception
 
 class httpspeer(httppeer):
     def __init__(self, ui, path):
         if not url.has_https:
             raise error.Abort(_('Python support for SSL and HTTPS '
                                'is not installed'))
         httppeer.__init__(self, ui, path)
 
 def instance(ui, path, create):
     if create:
         raise error.Abort(_('cannot create new http repository'))
     try:
         if path.startswith('https:'):
             inst = httpspeer(ui, path)
         else:
             inst = httppeer(ui, path)
         try:
             # Try to do useful work when checking compatibility.
             # Usually saves a roundtrip since we want the caps anyway.
             inst._fetchcaps()
         except error.RepoError:
             # No luck, try older compatibility check.
             inst.between([(nullid, nullid)])
         return inst
     except error.RepoError as httpexception:
         try:
             r = statichttprepo.instance(ui, "static-" + path, create)
             ui.note(_('(falling back to static-http)\n'))
             return r
         except error.RepoError:
             raise httpexception # use the original http RepoError instead