[RFC PATCH 19/19] qapi: Implement -compat deprecated-output=hide for events

[Markus Armbruster <armbru@redhat.com>]

This policy suppresses deprecated events, and thus permits "testing
the future".

No QMP event is deprecated right now.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
---
 qapi/common.json       |  4 ++--
 tests/test-qmp-event.c | 17 +++++++++++++++++
 qemu-options.hx        |  4 +++-
 scripts/qapi/events.py | 14 ++++++++++++--
 4 files changed, 34 insertions(+), 5 deletions(-)

diff --git a/qapi/common.json b/qapi/common.json
index 06e54642bb..4e3da4beee 100644
--- a/qapi/common.json
+++ b/qapi/common.json
@@ -167,14 +167,14 @@
 # Policy for handling "funny" output.
 #
 # @accept: Pass on unchanged
-# TODO @hide: Filter out
+# @hide: Filter out
 #
 # FIXME Guidance on intended use.
 #
 # Since: 4.2
 ##
 { 'enum': 'CompatPolicyOutput',
-  'data': [ 'accept' ] }
+  'data': [ 'accept', 'hide' ] }
 
 ##
 # @CompatPolicy:
diff --git a/tests/test-qmp-event.c b/tests/test-qmp-event.c
index 7dd0053190..303c8d6382 100644
--- a/tests/test-qmp-event.c
+++ b/tests/test-qmp-event.c
@@ -14,6 +14,7 @@
 #include "qemu/osdep.h"
 
 #include "qemu-common.h"
+#include "qapi/compat-policy.h"
 #include "qapi/error.h"
 #include "qapi/qmp/qbool.h"
 #include "qapi/qmp/qdict.h"
@@ -140,6 +141,21 @@ static void test_event_d(TestEventData *data,
     qobject_unref(data->expect);
 }
 
+static void test_event_deprecated(TestEventData *data, const void *unused)
+{
+    data->expect = qdict_from_jsonf_nofail("{ 'event': 'TEST-EVENT-FEATURES1' }");
+
+    qapi_event_send_test_event_features1();
+    g_assert(data->emitted);
+
+    qapi_compat_policy.deprecated_output = COMPAT_POLICY_OUTPUT_HIDE;
+    data->emitted = false;
+    qapi_event_send_test_event_features1();
+    g_assert(!data->emitted);
+
+    qobject_unref(data->expect);
+}
+
 int main(int argc, char **argv)
 {
     g_test_init(&argc, &argv, NULL);
@@ -148,6 +164,7 @@ int main(int argc, char **argv)
     event_test_add("/event/event_b", test_event_b);
     event_test_add("/event/event_c", test_event_c);
     event_test_add("/event/event_d", test_event_d);
+    event_test_add("/event/deprecated", test_event_deprecated);
     g_test_run();
 
     return 0;
diff --git a/qemu-options.hx b/qemu-options.hx
index 645629457a..c0128813c6 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -3320,7 +3320,7 @@ STEXI
 ETEXI
 
 DEF("compat", HAS_ARG, QEMU_OPTION_compat,
-    "-compat [deprecated-input=accept|reject|crash][,deprecated-output=accept]\n"
+    "-compat [deprecated-input=accept|reject|crash][,deprecated-output=accept|hide]\n"
     "                Policy for handling deprecated management interfaces\n",
     QEMU_ARCH_ALL)
 STEXI
@@ -3337,6 +3337,8 @@ Reject deprecated commands
 Crash on deprecated command
 @item deprecated-output=accept (default)
 Emit deprecated events
+@item deprecated-output=hide
+Suppress deprecated events
 @end table
 FIXME Guidance on intended use
 ETEXI
diff --git a/scripts/qapi/events.py b/scripts/qapi/events.py
index f64e61076e..5778fa1a0d 100644
--- a/scripts/qapi/events.py
+++ b/scripts/qapi/events.py
@@ -61,7 +61,8 @@ def gen_param_var(typ):
     return ret
 
 
-def gen_event_send(name, arg_type, boxed, event_enum_name, event_emit):
+def gen_event_send(name, arg_type, features, boxed,
+                   event_enum_name, event_emit):
     # FIXME: Our declaration of local variables (and of 'errp' in the
     # parameter list) can collide with exploded members of the event's
     # data type passed in as parameters.  If this collision ever hits in
@@ -86,6 +87,14 @@ def gen_event_send(name, arg_type, boxed, event_enum_name, event_emit):
         if not boxed:
             ret += gen_param_var(arg_type)
 
+    if 'deprecated' in [f.name for f in features]:
+        ret += mcgen('''
+
+    if (qapi_compat_policy.deprecated_output == COMPAT_POLICY_OUTPUT_HIDE) {
+        return;
+    }
+''')
+
     ret += mcgen('''
 
     qmp = qmp_event_build_dict("%(name)s");
@@ -154,6 +163,7 @@ class QAPISchemaGenEventVisitor(QAPISchemaModularCVisitor):
 #include "%(prefix)sqapi-emit-events.h"
 #include "%(events)s.h"
 #include "%(visit)s.h"
+#include "qapi/compat-policy.h"
 #include "qapi/error.h"
 #include "qapi/qmp/qdict.h"
 #include "qapi/qobject-output-visitor.h"
@@ -192,7 +202,7 @@ void %(event_emit)s(%(event_enum)s event, QDict *qdict);
     def visit_event(self, name, info, ifcond, features, arg_type, boxed):
         with ifcontext(ifcond, self._genh, self._genc):
             self._genh.add(gen_event_send_decl(name, arg_type, boxed))
-            self._genc.add(gen_event_send(name, arg_type, boxed,
+            self._genc.add(gen_event_send(name, arg_type, features, boxed,
                                           self._event_enum_name,
                                           self._event_emit_name))
         # Note: we generate the enum member regardless of @ifcond, to
-- 
2.21.0