wireprototypes: convert `baseprotocolhandler.name` to an abstract property

PyCharm was flagging the subclasses where this was declared as a `@property`
with

    Type of 'name' is incompatible with 'baseprotocolhandler'

But pytype didn't complain.  This seems more correct, however.  Since `Protocol`
is already an `abc.ABCMeta` class, we don't need to mess with the class
hierarchy.

mercurial/wireprototypes.py

@@ -1,457 +1,460
 # Copyright 2018 Gregory Szorc <[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 annotations
 
+import abc
 import typing
 
 from typing import (
     Protocol,
 )
 
 from .node import (
     bin,
     hex,
 )
 from .i18n import _
 from .thirdparty import attr
 
 # Force pytype to use the non-vendored package
 if typing.TYPE_CHECKING:
     # noinspection PyPackageRequirements
     import attr
 
 from . import (
     error,
     util,
 )
 from .utils import compression
 
 # Names of the SSH protocol implementations.
 SSHV1 = b'ssh-v1'
 
 NARROWCAP = b'exp-narrow-1'
 ELLIPSESCAP1 = b'exp-ellipses-1'
 ELLIPSESCAP = b'exp-ellipses-2'
 SUPPORTED_ELLIPSESCAP = (ELLIPSESCAP1, ELLIPSESCAP)
 
 # All available wire protocol transports.
 TRANSPORTS = {
     SSHV1: {
         b'transport': b'ssh',
         b'version': 1,
     },
     b'http-v1': {
         b'transport': b'http',
         b'version': 1,
     },
 }
 
 
 class bytesresponse:
     """A wire protocol response consisting of raw bytes."""
 
     def __init__(self, data):
         self.data = data
 
 
 class ooberror:
     """wireproto reply: failure of a batch of operation
 
     Something failed during a batch call. The error message is stored in
     `self.message`.
     """
 
     def __init__(self, message):
         self.message = message
 
 
 class pushres:
     """wireproto reply: success with simple integer return
 
     The call was successful and returned an integer contained in `self.res`.
     """
 
     def __init__(self, res, output):
         self.res = res
         self.output = output
 
 
 class pusherr:
     """wireproto reply: failure
 
     The call failed. The `self.res` attribute contains the error message.
     """
 
     def __init__(self, res, output):
         self.res = res
         self.output = output
 
 
 class streamres:
     """wireproto reply: binary stream
 
     The call was successful and the result is a stream.
 
     Accepts a generator containing chunks of data to be sent to the client.
 
     ``prefer_uncompressed`` indicates that the data is expected to be
     uncompressable and that the stream should therefore use the ``none``
     engine.
     """
 
     def __init__(self, gen=None, prefer_uncompressed=False):
         self.gen = gen
         self.prefer_uncompressed = prefer_uncompressed
 
 
 class streamreslegacy:
     """wireproto reply: uncompressed binary stream
 
     The call was successful and the result is a stream.
 
     Accepts a generator containing chunks of data to be sent to the client.
 
     Like ``streamres``, but sends an uncompressed data for "version 1" clients
     using the application/mercurial-0.1 media type.
     """
 
     def __init__(self, gen=None):
         self.gen = gen
 
 
 # list of nodes encoding / decoding
 def decodelist(l, sep=b' '):
     if l:
         return [bin(v) for v in l.split(sep)]
     return []
 
 
 def encodelist(l, sep=b' '):
     try:
         return sep.join(map(hex, l))
     except TypeError:
         raise
 
 
 # batched call argument encoding
 
 
 def escapebatcharg(plain):
     return (
         plain.replace(b':', b':c')
         .replace(b',', b':o')
         .replace(b';', b':s')
         .replace(b'=', b':e')
     )
 
 
 def unescapebatcharg(escaped):
     return (
         escaped.replace(b':e', b'=')
         .replace(b':s', b';')
         .replace(b':o', b',')
         .replace(b':c', b':')
     )
 
 
 # mapping of options accepted by getbundle and their types
 #
 # Meant to be extended by extensions. It is the extension's responsibility to
 # ensure such options are properly processed in exchange.getbundle.
 #
 # supported types are:
 #
 # :nodes: list of binary nodes, transmitted as space-separated hex nodes
 # :csv:   list of values, transmitted as comma-separated values
 # :scsv:  set of values, transmitted as comma-separated values
 # :plain: string with no transformation needed.
 GETBUNDLE_ARGUMENTS = {
     b'heads': b'nodes',
     b'bookmarks': b'boolean',
     b'common': b'nodes',
     b'obsmarkers': b'boolean',
     b'phases': b'boolean',
     b'bundlecaps': b'scsv',
     b'listkeys': b'csv',
     b'cg': b'boolean',
     b'cbattempted': b'boolean',
     b'stream': b'boolean',
     b'includepats': b'csv',
     b'excludepats': b'csv',
 }
 
 
 class baseprotocolhandler(Protocol):
     """Abstract base class for wire protocol handlers.
 
     A wire protocol handler serves as an interface between protocol command
     handlers and the wire protocol transport layer. Protocol handlers provide
     methods to read command arguments, redirect stdio for the duration of
     the request, handle response types, etc.
     """
 
-    name: bytes
-    """The name of the protocol implementation.
+    @property
+    @abc.abstractmethod
+    def name(self) -> bytes:
+        """The name of the protocol implementation.
 
-    Used for uniquely identifying the transport type.
-    """
+        Used for uniquely identifying the transport type.
+        """
 
     def getargs(self, args):
         """return the value for arguments in <args>
 
         For version 1 transports, returns a list of values in the same
         order they appear in ``args``. For version 2 transports, returns
         a dict mapping argument name to value.
         """
 
     def getprotocaps(self):
         """Returns the list of protocol-level capabilities of client
 
         Returns a list of capabilities as declared by the client for
         the current request (or connection for stateful protocol handlers)."""
 
     def getpayload(self):
         """Provide a generator for the raw payload.
 
         The caller is responsible for ensuring that the full payload is
         processed.
         """
 
     def mayberedirectstdio(self):
         """Context manager to possibly redirect stdio.
 
         The context manager yields a file-object like object that receives
         stdout and stderr output when the context manager is active. Or it
         yields ``None`` if no I/O redirection occurs.
 
         The intent of this context manager is to capture stdio output
         so it may be sent in the response. Some transports support streaming
         stdio to the client in real time. For these transports, stdio output
         won't be captured.
         """
 
     def client(self):
         """Returns a string representation of this client (as bytes)."""
 
     def addcapabilities(self, repo, caps):
         """Adds advertised capabilities specific to this protocol.
 
         Receives the list of capabilities collected so far.
 
         Returns a list of capabilities. The passed in argument can be returned.
         """
 
     def checkperm(self, perm):
         """Validate that the client has permissions to perform a request.
 
         The argument is the permission required to proceed. If the client
         doesn't have that permission, the exception should raise or abort
         in a protocol specific manner.
         """
 
 
 class commandentry:
     """Represents a declared wire protocol command."""
 
     def __init__(
         self,
         func,
         args=b'',
         transports=None,
         permission=b'push',
         cachekeyfn=None,
         extracapabilitiesfn=None,
     ):
         self.func = func
         self.args = args
         self.transports = transports or set()
         self.permission = permission
         self.cachekeyfn = cachekeyfn
         self.extracapabilitiesfn = extracapabilitiesfn
 
     def _merge(self, func, args):
         """Merge this instance with an incoming 2-tuple.
 
         This is called when a caller using the old 2-tuple API attempts
         to replace an instance. The incoming values are merged with
         data not captured by the 2-tuple and a new instance containing
         the union of the two objects is returned.
         """
         return commandentry(
             func,
             args=args,
             transports=set(self.transports),
             permission=self.permission,
         )
 
     # Old code treats instances as 2-tuples. So expose that interface.
     def __iter__(self):
         yield self.func
         yield self.args
 
     def __getitem__(self, i):
         if i == 0:
             return self.func
         elif i == 1:
             return self.args
         else:
             raise IndexError(b'can only access elements 0 and 1')
 
 
 class commanddict(dict):
     """Container for registered wire protocol commands.
 
     It behaves like a dict. But __setitem__ is overwritten to allow silent
     coercion of values from 2-tuples for API compatibility.
     """
 
     def __setitem__(self, k, v):
         if isinstance(v, commandentry):
             pass
         # Cast 2-tuples to commandentry instances.
         elif isinstance(v, tuple):
             if len(v) != 2:
                 raise ValueError(b'command tuples must have exactly 2 elements')
 
             # It is common for extensions to wrap wire protocol commands via
             # e.g. ``wireproto.commands[x] = (newfn, args)``. Because callers
             # doing this aren't aware of the new API that uses objects to store
             # command entries, we automatically merge old state with new.
             if k in self:
                 v = self[k]._merge(v[0], v[1])
             else:
                 # Use default values from @wireprotocommand.
                 v = commandentry(
                     v[0],
                     args=v[1],
                     transports=set(TRANSPORTS),
                     permission=b'push',
                 )
         else:
             raise ValueError(
                 b'command entries must be commandentry instances '
                 b'or 2-tuples'
             )
 
         return super(commanddict, self).__setitem__(k, v)
 
     def commandavailable(self, command, proto):
         """Determine if a command is available for the requested protocol."""
         assert proto.name in TRANSPORTS
 
         entry = self.get(command)
 
         if not entry:
             return False
 
         if proto.name not in entry.transports:
             return False
 
         return True
 
 
 def supportedcompengines(ui, role):
     """Obtain the list of supported compression engines for a request."""
     assert role in (compression.CLIENTROLE, compression.SERVERROLE)
 
     compengines = compression.compengines.supportedwireengines(role)
 
     # Allow config to override default list and ordering.
     if role == compression.SERVERROLE:
         configengines = ui.configlist(b'server', b'compressionengines')
         config = b'server.compressionengines'
     else:
         # This is currently implemented mainly to facilitate testing. In most
         # cases, the server should be in charge of choosing a compression engine
         # because a server has the most to lose from a sub-optimal choice. (e.g.
         # CPU DoS due to an expensive engine or a network DoS due to poor
         # compression ratio).
         configengines = ui.configlist(
             b'experimental', b'clientcompressionengines'
         )
         config = b'experimental.clientcompressionengines'
 
     # No explicit config. Filter out the ones that aren't supposed to be
     # advertised and return default ordering.
     if not configengines:
         attr = 'serverpriority' if role == util.SERVERROLE else 'clientpriority'
         return [
             e for e in compengines if getattr(e.wireprotosupport(), attr) > 0
         ]
 
     # If compression engines are listed in the config, assume there is a good
     # reason for it (like server operators wanting to achieve specific
     # performance characteristics). So fail fast if the config references
     # unusable compression engines.
     validnames = {e.name() for e in compengines}
     invalidnames = {e for e in configengines if e not in validnames}
     if invalidnames:
         raise error.Abort(
             _(b'invalid compression engine defined in %s: %s')
             % (config, b', '.join(sorted(invalidnames)))
         )
 
     compengines = [e for e in compengines if e.name() in configengines]
     compengines = sorted(
         compengines, key=lambda e: configengines.index(e.name())
     )
 
     if not compengines:
         raise error.Abort(
             _(
                 b'%s config option does not specify any known '
                 b'compression engines'
             )
             % config,
             hint=_(b'usable compression engines: %s')
             % b', '.sorted(validnames),  # pytype: disable=attribute-error
         )
 
     return compengines
 
 
 @attr.s
 class encodedresponse:
     """Represents response data that is already content encoded.
 
     Wire protocol version 2 only.
 
     Commands typically emit Python objects that are encoded and sent over the
     wire. If commands emit an object of this type, the encoding step is bypassed
     and the content from this object is used instead.
     """
 
     data = attr.ib()
 
 
 @attr.s
 class alternatelocationresponse:
     """Represents a response available at an alternate location.
 
     Instances are sent in place of actual response objects when the server
     is sending a "content redirect" response.
 
     Only compatible with wire protocol version 2.
     """
 
     url = attr.ib()
     mediatype = attr.ib()
     size = attr.ib(default=None)
     fullhashes = attr.ib(default=None)
     fullhashseed = attr.ib(default=None)
     serverdercerts = attr.ib(default=None)
     servercadercerts = attr.ib(default=None)
 
 
 @attr.s
 class indefinitebytestringresponse:
     """Represents an object to be encoded to an indefinite length bytestring.
 
     Instances are initialized from an iterable of chunks, with each chunk being
     a bytes instance.
     """
 
     chunks = attr.ib()