qapi: add conditions to VNC type/commands/events on the schema

Add #if defined(CONFIG_VNC) in generated code, and adjust the
qmp/hmp code accordingly.

query-qmp-schema no longer reports the command/events etc as
available when disabled at compile.

Commands made conditional:

* query-vnc, query-vnc-servers, change-vnc-password

  Before the patch, the commands for !CONFIG_VNC are stubs that fail
  like this:

    {"error": {"class": "GenericError",
               "desc": "The feature 'vnc' is not enabled"}}

  Afterwards, they fail like this:

    {"error": {"class": "CommandNotFound",
               "desc": "The command FOO has not been found"}}

  I call that an improvement, because it lets clients distinguish
  between command unavailable (class CommandNotFound) and command failed
  (class GenericError).

Events made conditional:

* VNC_CONNECTED, VNC_INITIALIZED, VNC_DISCONNECTED

HMP change:

* info vnc

  Will return "unknown command: 'info vnc'" when VNC is compiled
  out (same as error for spice when --disable-spice)

Occurrences of VNC (case insensitive) in the schema that aren't
covered by this change:

* add_client

  Command has other uses, including "socket bases character devices".
  These are unconditional as far as I can tell.

* set_password, expire_password

  In theory, these commands could be used for managing any service's
  password.  In practice, they're used for VNC and SPICE services.
  They're documented for "remote display session" / "remote display
  server".

  The service is selected by argument @protocol.  The code special-cases
  protocol-specific argument checking, then calls a protocol-specific
  function to do the work.  If it fails, the command fails with "Could
  not set password".  It does when the service isn't compiled in (it's a
  stub then).

  We could make these commands conditional on the conjunction of all
  services [currently: defined(CONFIG_VNC) || defined(CONFIG_SPICE)],
  but I doubt it's worthwhile.

* change

  Command has other uses, namely changing media.
  This patch inlines a stub; no functional change.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20180703155648.11933-14-marcandre.lureau@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>

qapi/ui.json

@@ -377,7 +377,8 @@
   'data': { 'host': 'str',
             'service': 'str',
             'family': 'NetworkAddressFamily',
-            'websocket': 'bool' } }
+            'websocket': 'bool' },
+  'if': 'defined(CONFIG_VNC)' }
 
 ##
 # @VncServerInfo:
@@ -391,7 +392,8 @@
 ##
 { 'struct': 'VncServerInfo',
   'base': 'VncBasicInfo',
-  'data': { '*auth': 'str' } }
+  'data': { '*auth': 'str' },
+  'if': 'defined(CONFIG_VNC)' }
 
 ##
 # @VncClientInfo:
@@ -408,7 +410,8 @@
 ##
 { 'struct': 'VncClientInfo',
   'base': 'VncBasicInfo',
-  'data': { '*x509_dname': 'str', '*sasl_username': 'str' } }
+  'data': { '*x509_dname': 'str', '*sasl_username': 'str' },
+  'if': 'defined(CONFIG_VNC)' }
 
 ##
 # @VncInfo:
@@ -449,7 +452,8 @@
 { 'struct': 'VncInfo',
   'data': {'enabled': 'bool', '*host': 'str',
            '*family': 'NetworkAddressFamily',
-           '*service': 'str', '*auth': 'str', '*clients': ['VncClientInfo']} }
+           '*service': 'str', '*auth': 'str', '*clients': ['VncClientInfo']},
+  'if': 'defined(CONFIG_VNC)' }
 
 ##
 # @VncPrimaryAuth:
@@ -460,7 +464,8 @@
 ##
 { 'enum': 'VncPrimaryAuth',
   'data': [ 'none', 'vnc', 'ra2', 'ra2ne', 'tight', 'ultra',
-            'tls', 'vencrypt', 'sasl' ] }
+            'tls', 'vencrypt', 'sasl' ],
+  'if': 'defined(CONFIG_VNC)' }
 
 ##
 # @VncVencryptSubAuth:
@@ -474,8 +479,8 @@
             'tls-none',  'x509-none',
             'tls-vnc',   'x509-vnc',
             'tls-plain', 'x509-plain',
-            'tls-sasl',  'x509-sasl' ] }
-
+            'tls-sasl',  'x509-sasl' ],
+  'if': 'defined(CONFIG_VNC)' }
 
 ##
 # @VncServerInfo2:
@@ -492,8 +497,8 @@
 { 'struct': 'VncServerInfo2',
   'base': 'VncBasicInfo',
   'data': { 'auth'      : 'VncPrimaryAuth',
-            '*vencrypt' : 'VncVencryptSubAuth' } }
-
+            '*vencrypt' : 'VncVencryptSubAuth' },
+  'if': 'defined(CONFIG_VNC)' }
 
 ##
 # @VncInfo2:
@@ -525,7 +530,8 @@
             'clients'   : ['VncClientInfo'],
             'auth'      : 'VncPrimaryAuth',
             '*vencrypt' : 'VncVencryptSubAuth',
-            '*display'  : 'str' } }
+            '*display'  : 'str' },
+  'if': 'defined(CONFIG_VNC)' }
 
 ##
 # @query-vnc:
@@ -556,8 +562,8 @@
 #    }
 #
 ##
-{ 'command': 'query-vnc', 'returns': 'VncInfo' }
-
+{ 'command': 'query-vnc', 'returns': 'VncInfo',
+  'if': 'defined(CONFIG_VNC)' }
 ##
 # @query-vnc-servers:
 #
@@ -567,7 +573,8 @@
 #
 # Since: 2.3
 ##
-{ 'command': 'query-vnc-servers', 'returns': ['VncInfo2'] }
+{ 'command': 'query-vnc-servers', 'returns': ['VncInfo2'],
+  'if': 'defined(CONFIG_VNC)' }
 
 ##
 # @change-vnc-password:
@@ -581,7 +588,8 @@
 # Notes:  An empty password in this command will set the password to the empty
 #         string.  Existing clients are unaffected by executing this command.
 ##
-{ 'command': 'change-vnc-password', 'data': {'password': 'str'} }
+{ 'command': 'change-vnc-password', 'data': {'password': 'str'},
+  'if': 'defined(CONFIG_VNC)' }
 
 ##
 # @VNC_CONNECTED:
@@ -610,7 +618,8 @@
 ##
 { 'event': 'VNC_CONNECTED',
   'data': { 'server': 'VncServerInfo',
-            'client': 'VncBasicInfo' } }
+            'client': 'VncBasicInfo' },
+  'if': 'defined(CONFIG_VNC)' }
 
 ##
 # @VNC_INITIALIZED:
@@ -637,7 +646,8 @@
 ##
 { 'event': 'VNC_INITIALIZED',
   'data': { 'server': 'VncServerInfo',
-            'client': 'VncClientInfo' } }
+            'client': 'VncClientInfo' },
+  'if': 'defined(CONFIG_VNC)' }
 
 ##
 # @VNC_DISCONNECTED:
@@ -663,7 +673,8 @@
 ##
 { 'event': 'VNC_DISCONNECTED',
   'data': { 'server': 'VncServerInfo',
-            'client': 'VncClientInfo' } }
+            'client': 'VncClientInfo' },
+  'if': 'defined(CONFIG_VNC)' }
 
 ##
 # = Input