[PULL 05/11] qapi: Implement deprecated-output=hide for QMP event data

[Markus Armbruster <armbru@redhat.com>]

This policy suppresses deprecated bits in output, and thus permits
"testing the future".  Implement it for QMP event data: suppress
deprecated members.

No QMP event data is deprecated right now.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20210312153210.2810514-5-armbru@redhat.com>
---
 tests/unit/test-qmp-event.c             | 21 +++++++++++++++++++++
 scripts/qapi/events.py                  |  8 ++++++--
 tests/qapi-schema/qapi-schema-test.json |  3 +++
 tests/qapi-schema/qapi-schema-test.out  |  2 ++
 4 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/tests/unit/test-qmp-event.c b/tests/unit/test-qmp-event.c
index ab059fb5c2..047f44ff9a 100644
--- a/tests/unit/test-qmp-event.c
+++ b/tests/unit/test-qmp-event.c
@@ -159,6 +159,26 @@ static void test_event_deprecated(TestEventData *data, const void *unused)
     qobject_unref(data->expect);
 }
 
+static void test_event_deprecated_data(TestEventData *data, const void *unused)
+{
+    memset(&compat_policy, 0, sizeof(compat_policy));
+
+    data->expect = qdict_from_jsonf_nofail("{ 'event': 'TEST-EVENT-FEATURES0',"
+                                           " 'data': { 'foo': 42 } }");
+    qapi_event_send_test_event_features0(42);
+    g_assert(data->emitted);
+
+    qobject_unref(data->expect);
+
+    compat_policy.has_deprecated_output = true;
+    compat_policy.deprecated_output = COMPAT_POLICY_OUTPUT_HIDE;
+    data->expect = qdict_from_jsonf_nofail("{ 'event': 'TEST-EVENT-FEATURES0' }");
+    qapi_event_send_test_event_features0(42);
+    g_assert(data->emitted);
+
+    qobject_unref(data->expect);
+}
+
 int main(int argc, char **argv)
 {
     g_test_init(&argc, &argv, NULL);
@@ -168,6 +188,7 @@ int main(int argc, char **argv)
     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);
+    event_test_add("/event/deprecated_data", test_event_deprecated_data);
     g_test_run();
 
     return 0;
diff --git a/scripts/qapi/events.py b/scripts/qapi/events.py
index f6e1e76f64..8335c2bdfc 100644
--- a/scripts/qapi/events.py
+++ b/scripts/qapi/events.py
@@ -126,7 +126,7 @@ def gen_event_send(name: str,
     if have_args:
         assert arg_type is not None
         ret += mcgen('''
-    v = qobject_output_visitor_new(&obj);
+    v = qobject_output_visitor_new_qmp(&obj);
 ''')
         if not arg_type.is_implicit():
             ret += mcgen('''
@@ -145,7 +145,11 @@ def gen_event_send(name: str,
         ret += mcgen('''
 
     visit_complete(v, &obj);
-    qdict_put_obj(qmp, "data", obj);
+    if (qdict_size(qobject_to(QDict, obj))) {
+        qdict_put_obj(qmp, "data", obj);
+    } else {
+        qobject_unref(obj);
+    }
 ''')
 
     ret += mcgen('''
diff --git a/tests/qapi-schema/qapi-schema-test.json b/tests/qapi-schema/qapi-schema-test.json
index 48a0adabae..12ec588b52 100644
--- a/tests/qapi-schema/qapi-schema-test.json
+++ b/tests/qapi-schema/qapi-schema-test.json
@@ -324,5 +324,8 @@
   'features': [ { 'name': 'feature1', 'if': [ 'defined(TEST_IF_COND_1)',
                                               'defined(TEST_IF_COND_2)'] } ] }
 
+{ 'event': 'TEST-EVENT-FEATURES0',
+  'data': 'FeatureStruct1' }
+
 { 'event': 'TEST-EVENT-FEATURES1',
   'features': [ 'deprecated' ] }
diff --git a/tests/qapi-schema/qapi-schema-test.out b/tests/qapi-schema/qapi-schema-test.out
index 776d737891..f5741df97f 100644
--- a/tests/qapi-schema/qapi-schema-test.out
+++ b/tests/qapi-schema/qapi-schema-test.out
@@ -440,6 +440,8 @@ command test-command-cond-features3 None -> None
     gen=True success_response=True boxed=False oob=False preconfig=False
     feature feature1
         if ['defined(TEST_IF_COND_1)', 'defined(TEST_IF_COND_2)']
+event TEST-EVENT-FEATURES0 FeatureStruct1
+    boxed=False
 event TEST-EVENT-FEATURES1 None
     boxed=False
     feature deprecated
-- 
2.26.2