qapi: Implement deprecated-output=hide for QMP command results

This policy suppresses deprecated bits in output, and thus permits
"testing the future".  Implement it for QMP command results.  Example:
when QEMU is run with -compat deprecated-output=hide, then

    {"execute": "query-cpus-fast"}

yields

    {"return": [{"thread-id": 9805, "props": {"core-id": 0, "thread-id": 0, "socket-id": 0}, "qom-path": "/machine/unattached/device[0]", "cpu-index": 0, "target": "x86_64"}]}

instead of

    {"return": [{"arch": "x86", "thread-id": 22436, "props": {"core-id": 0, "thread-id": 0, "socket-id": 0}, "qom-path": "/machine/unattached/device[0]", "cpu-index": 0, "target": "x86_64"}]}

Note the suppression of deprecated member "arch".

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20210318155519.1224118-4-armbru@redhat.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/scripts/qapi/visit.py b/scripts/qapi/visit.py
index 9aa0b1e11e..9d83bf650f 100644
--- a/scripts/qapi/visit.py
+++ b/scripts/qapi/visit.py
@@ -77,6 +77,7 @@ bool visit_type_%(c_name)s_members(Visitor *v, %(c_name)s *obj, Error **errp)
                      c_type=base.c_name())
 
     for memb in members:
+        deprecated = 'deprecated' in [f.name for f in memb.features]
         ret += gen_if(memb.ifcond)
         if memb.optional:
             ret += mcgen('''
@@ -84,6 +85,12 @@ bool visit_type_%(c_name)s_members(Visitor *v, %(c_name)s *obj, Error **errp)
 ''',
                          name=memb.name, c_name=c_name(memb.name))
             indent.increase()
+        if deprecated:
+            ret += mcgen('''
+    if (visit_deprecated(v, "%(name)s")) {
+''',
+                         name=memb.name)
+            indent.increase()
         ret += mcgen('''
     if (!visit_type_%(c_type)s(v, "%(name)s", &obj->%(c_name)s, errp)) {
         return false;
@@ -91,6 +98,11 @@ bool visit_type_%(c_name)s_members(Visitor *v, %(c_name)s *obj, Error **errp)
 ''',
                      c_type=memb.type.c_name(), name=memb.name,
                      c_name=c_name(memb.name))
+        if deprecated:
+            indent.decrease()
+            ret += mcgen('''
+    }
+''')
         if memb.optional:
             indent.decrease()
             ret += mcgen('''