wireproto: define and expose types of wire command arguments

Exposing the set of argument names is cool. But with wire protocol
version 2, we're using CBOR to transport arguments and this allows us
to have typing for arguments.

Typed arguments are much nicer because they will cut down on transfer
overhead and processing overhead for decoding values.

This commit teaches @wireprotocommand to accept a dictionary for
arguments. The arguments registered for version 2 transports are
canonically stored as dictionaries rather than a space-delimited string.

It is an error to defined arguments with a dictionary for commands using
version 1 transports. This reinforces my intent to fully decouple command
handlers for version 2 transports.

Differential Revision: https://phab.mercurial-scm.org/D3202

mercurial/help/internals/wireprotocol.txt

@@ -1712,7 +1712,12 b' commands'
    are:
 
       args
-         An array of argument names accepted by this command.
+         A map of argument names and their expected types.
+
+         Types are defined as a representative value for the expected type.
+         e.g. an argument expecting a boolean type will have its value
+         set to true. An integer type will have its value set to 42. The
+         actual values are arbitrary and may not have meaning.
       permissions
          An array of permissions required to execute this command.
 

mercurial/wireproto.py

@@ -713,8 +713,11 b" def wireprotocommand(name, args='', tran"
 
     ``name`` is the name of the wire protocol command being provided.
 
-    ``args`` is a space-delimited list of named arguments that the command
-    accepts. ``*`` is a special value that says to accept all arguments.
+    ``args`` defines the named arguments accepted by the command. It is
+    ideally a dict mapping argument names to their types. For backwards
+    compatibility, it can be a space-delimited list of argument names. For
+    version 1 transports, ``*`` denotes a special value that says to accept
+    all named arguments.
 
     ``transportpolicy`` is a POLICY_* constant denoting which transports
     this wire protocol command should be exposed to. By default, commands
@@ -752,6 +755,17 b" def wireprotocommand(name, args='', tran"
                                      'got %s; expected "push" or "pull"' %
                                      permission)
 
+    if 1 in transportversions and not isinstance(args, bytes):
+        raise error.ProgrammingError('arguments for version 1 commands must '
+                                     'be declared as bytes')
+
+    if isinstance(args, bytes):
+        dictargs = {arg: b'legacy' for arg in args.split()}
+    elif isinstance(args, dict):
+        dictargs = args
+    else:
+        raise ValueError('args must be bytes or a dict')
+
     def register(func):
         if 1 in transportversions:
             if name in commands:
@@ -764,7 +778,8 b" def wireprotocommand(name, args='', tran"
             if name in commandsv2:
                 raise error.ProgrammingError('%s command already registered '
                                              'for version 2' % name)
-            commandsv2[name] = commandentry(func, args=args,
+
+            commandsv2[name] = commandentry(func, args=dictargs,
                                             transports=transports,
                                             permission=permission)
 
@@ -1304,7 +1319,7 b' def _capabilitiesv2(repo, proto):'
 
     for command, entry in commandsv2.items():
         caps['commands'][command] = {
-            'args': sorted(entry.args.split()) if entry.args else [],
+            'args': entry.args,
             'permissions': [entry.permission],
         }
 
@@ -1325,7 +1340,11 b' def capabilitiesv2(repo, proto):'
 
     return wireprototypes.cborresponse(caps)
 
-@wireprotocommand('heads', args='publiconly', permission='pull',
+@wireprotocommand('heads',
+                  args={
+                      'publiconly': False,
+                  },
+                  permission='pull',
                   transportpolicy=POLICY_V2_ONLY)
 def headsv2(repo, proto, publiconly=False):
     if publiconly:
@@ -1333,14 +1352,22 b' def headsv2(repo, proto, publiconly=Fals'
 
     return wireprototypes.cborresponse(repo.heads())
 
-@wireprotocommand('known', 'nodes', permission='pull',
+@wireprotocommand('known',
+                  args={
+                      'nodes': [b'deadbeef'],
+                  },
+                  permission='pull',
                   transportpolicy=POLICY_V2_ONLY)
 def knownv2(repo, proto, nodes=None):
     nodes = nodes or []
     result = b''.join(b'1' if n else b'0' for n in repo.known(nodes))
     return wireprototypes.cborresponse(result)
 
-@wireprotocommand('listkeys', 'namespace', permission='pull',
+@wireprotocommand('listkeys',
+                  args={
+                      'namespace': b'ns',
+                  },
+                  permission='pull',
                   transportpolicy=POLICY_V2_ONLY)
 def listkeysv2(repo, proto, namespace=None):
     keys = repo.listkeys(encoding.tolocal(namespace))

mercurial/wireprotoserver.py

@@ -606,10 +606,11 b' class httpv2protocolhandler(object):'
 
     def getargs(self, args):
         data = {}
-        for k in args.split():
+        for k, typ in args.items():
             if k == '*':
                 raise NotImplementedError('do not support * args')
             elif k in self._args:
+                # TODO consider validating value types.
                 data[k] = self._args[k]
 
         return data

tests/test-wireproto-command-capabilities.t

@@ -30,11 +30,11 b' capabilities request returns an array of'
   s>     \r\n
   s>     *\r\n (glob)
   s>     *\x00\x01\x00\x02\x01F (glob)
-  s>     \xa2Hcommands\xaaEheads\xa2Dargs\x81JpubliconlyKpermissions\x81DpullEknown\xa2Dargs\x81EnodesKpermissions\x81DpullFlookup\xa2Dargs\x81CkeyKpermissions\x81DpullGpushkey\xa2Dargs\x84CkeyInamespaceCnewColdKpermissions\x81DpushHlistkeys\xa2Dargs\x81InamespaceKpermissions\x81DpullHunbundle\xa2Dargs\x81EheadsKpermissions\x81DpushIbranchmap\xa2Dargs\x80Kpermissions\x81DpullIgetbundle\xa2Dargs\x81A*Kpermissions\x81DpullLcapabilities\xa2Dargs\x80Kpermissions\x81DpullLclonebundles\xa2Dargs\x80Kpermissions\x81DpullKcompression\x82\xa1DnameDzstd\xa1DnameDzlib
+  s>     \xa2Hcommands\xaaEheads\xa2Dargs\xa1Jpubliconly\xf4Kpermissions\x81DpullEknown\xa2Dargs\xa1Enodes\x81HdeadbeefKpermissions\x81DpullFlookup\xa2Dargs\xa1CkeyFlegacyKpermissions\x81DpullGpushkey\xa2Dargs\xa4CkeyFlegacyCnewFlegacyColdFlegacyInamespaceFlegacyKpermissions\x81DpushHlistkeys\xa2Dargs\xa1InamespaceBnsKpermissions\x81DpullHunbundle\xa2Dargs\xa1EheadsFlegacyKpermissions\x81DpushIbranchmap\xa2Dargs\xa0Kpermissions\x81DpullIgetbundle\xa2Dargs\xa1A*FlegacyKpermissions\x81DpullLcapabilities\xa2Dargs\xa0Kpermissions\x81DpullLclonebundles\xa2Dargs\xa0Kpermissions\x81DpullKcompression\x82\xa1DnameDzstd\xa1DnameDzlib
   s>     \r\n
   received frame(size=*; request=1; stream=2; streamflags=stream-begin; type=bytes-response; flags=eos|cbor) (glob)
   s>     0\r\n
   s>     \r\n
-  response: [{b'commands': {b'branchmap': {b'args': [], b'permissions': [b'pull']}, b'capabilities': {b'args': [], b'permissions': [b'pull']}, b'clonebundles': {b'args': [], b'permissions': [b'pull']}, b'getbundle': {b'args': [b'*'], b'permissions': [b'pull']}, b'heads': {b'args': [b'publiconly'], b'permissions': [b'pull']}, b'known': {b'args': [b'nodes'], b'permissions': [b'pull']}, b'listkeys': {b'args': [b'namespace'], b'permissions': [b'pull']}, b'lookup': {b'args': [b'key'], b'permissions': [b'pull']}, b'pushkey': {b'args': [b'key', b'namespace', b'new', b'old'], b'permissions': [b'push']}, b'unbundle': {b'args': [b'heads'], b'permissions': [b'push']}}, b'compression': [{b'name': b'zstd'}, {b'name': b'zlib'}]}]
+  response: [{b'commands': {b'branchmap': {b'args': {}, b'permissions': [b'pull']}, b'capabilities': {b'args': {}, b'permissions': [b'pull']}, b'clonebundles': {b'args': {}, b'permissions': [b'pull']}, b'getbundle': {b'args': {b'*': b'legacy'}, b'permissions': [b'pull']}, b'heads': {b'args': {b'publiconly': False}, b'permissions': [b'pull']}, b'known': {b'args': {b'nodes': [b'deadbeef']}, b'permissions': [b'pull']}, b'listkeys': {b'args': {b'namespace': b'ns'}, b'permissions': [b'pull']}, b'lookup': {b'args': {b'key': b'legacy'}, b'permissions': [b'pull']}, b'pushkey': {b'args': {b'key': b'legacy', b'namespace': b'legacy', b'new': b'legacy', b'old': b'legacy'}, b'permissions': [b'push']}, b'unbundle': {b'args': {b'heads': b'legacy'}, b'permissions': [b'push']}}, b'compression': [{b'name': b'zstd'}, {b'name': b'zlib'}]}]
 
   $ cat error.log