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>

3 files changed, 55 insertions, 22 deletions

diff --git a/tests/qapi-schema/qapi-schema-test.json b/tests/qapi-schema/qapi-schema-test.json
index 63f92adf68..48a0adabae 100644
--- a/tests/qapi-schema/qapi-schema-test.json
+++ b/tests/qapi-schema/qapi-schema-test.json
@@ -299,14 +299,15 @@
   'features': [ 'feature1' ] }
 
 { 'command': 'test-features0',
-  'data': { 'fs0': 'FeatureStruct0',
-            'fs1': 'FeatureStruct1',
-            'fs2': 'FeatureStruct2',
-            'fs3': 'FeatureStruct3',
-            'fs4': 'FeatureStruct4',
-            'cfs1': 'CondFeatureStruct1',
-            'cfs2': 'CondFeatureStruct2',
-            'cfs3': 'CondFeatureStruct3' },
+  'data': { '*fs0': 'FeatureStruct0',
+            '*fs1': 'FeatureStruct1',
+            '*fs2': 'FeatureStruct2',
+            '*fs3': 'FeatureStruct3',
+            '*fs4': 'FeatureStruct4',
+            '*cfs1': 'CondFeatureStruct1',
+            '*cfs2': 'CondFeatureStruct2',
+            '*cfs3': 'CondFeatureStruct3' },
+  'returns': 'FeatureStruct1',
   'features': [] }
 
 { 'command': 'test-command-features1',
diff --git a/tests/qapi-schema/qapi-schema-test.out b/tests/qapi-schema/qapi-schema-test.out
index 3b1387d9f1..776d737891 100644
--- a/tests/qapi-schema/qapi-schema-test.out
+++ b/tests/qapi-schema/qapi-schema-test.out
@@ -409,15 +409,15 @@ alternate FeatureAlternate1
     case eins: FeatureStruct1
     feature feature1
 object q_obj_test-features0-arg
-    member fs0: FeatureStruct0 optional=False
-    member fs1: FeatureStruct1 optional=False
-    member fs2: FeatureStruct2 optional=False
-    member fs3: FeatureStruct3 optional=False
-    member fs4: FeatureStruct4 optional=False
-    member cfs1: CondFeatureStruct1 optional=False
-    member cfs2: CondFeatureStruct2 optional=False
-    member cfs3: CondFeatureStruct3 optional=False
-command test-features0 q_obj_test-features0-arg -> None
+    member fs0: FeatureStruct0 optional=True
+    member fs1: FeatureStruct1 optional=True
+    member fs2: FeatureStruct2 optional=True
+    member fs3: FeatureStruct3 optional=True
+    member fs4: FeatureStruct4 optional=True
+    member cfs1: CondFeatureStruct1 optional=True
+    member cfs2: CondFeatureStruct2 optional=True
+    member cfs3: CondFeatureStruct3 optional=True
+command test-features0 q_obj_test-features0-arg -> FeatureStruct1
     gen=True success_response=True boxed=False oob=False preconfig=False
 command test-command-features1 None -> None
     gen=True success_response=True boxed=False oob=False preconfig=False
diff --git a/tests/unit/test-qmp-cmds.c b/tests/unit/test-qmp-cmds.c
index d3413bfef0..1079d35122 100644
--- a/tests/unit/test-qmp-cmds.c
+++ b/tests/unit/test-qmp-cmds.c
@@ -1,4 +1,5 @@
 #include "qemu/osdep.h"
+#include "qapi/compat-policy.h"
 #include "qapi/qmp/qdict.h"
 #include "qapi/qmp/qjson.h"
 #include "qapi/qmp/qnum.h"
@@ -49,12 +50,17 @@ void qmp_user_def_cmd1(UserDefOne * ud1, Error **errp)
 {
 }
 
-void qmp_test_features0(FeatureStruct0 *fs0, FeatureStruct1 *fs1,
-                       FeatureStruct2 *fs2, FeatureStruct3 *fs3,
-                       FeatureStruct4 *fs4, CondFeatureStruct1 *cfs1,
-                       CondFeatureStruct2 *cfs2, CondFeatureStruct3 *cfs3,
-                       Error **errp)
+FeatureStruct1 *qmp_test_features0(bool has_fs0, FeatureStruct0 *fs0,
+                                   bool has_fs1, FeatureStruct1 *fs1,
+                                   bool has_fs2, FeatureStruct2 *fs2,
+                                   bool has_fs3, FeatureStruct3 *fs3,
+                                   bool has_fs4, FeatureStruct4 *fs4,
+                                   bool has_cfs1, CondFeatureStruct1 *cfs1,
+                                   bool has_cfs2, CondFeatureStruct2 *cfs2,
+                                   bool has_cfs3, CondFeatureStruct3 *cfs3,
+                                   Error **errp)
 {
+    return g_new0(FeatureStruct1, 1);
 }
 
 void qmp_test_command_features1(Error **errp)
@@ -275,6 +281,30 @@ static void test_dispatch_cmd_io(void)
     qobject_unref(ret3);
 }
 
+static void test_dispatch_cmd_ret_deprecated(void)
+{
+    const char *cmd = "{ 'execute': 'test-features0' }";
+    QDict *ret;
+
+    memset(&compat_policy, 0, sizeof(compat_policy));
+
+    /* default accept */
+    ret = qobject_to(QDict, do_qmp_dispatch(false, cmd));
+    assert(ret && qdict_size(ret) == 1);
+    qobject_unref(ret);
+
+    compat_policy.has_deprecated_output = true;
+    compat_policy.deprecated_output = COMPAT_POLICY_OUTPUT_ACCEPT;
+    ret = qobject_to(QDict, do_qmp_dispatch(false, cmd));
+    assert(ret && qdict_size(ret) == 1);
+    qobject_unref(ret);
+
+    compat_policy.deprecated_output = COMPAT_POLICY_OUTPUT_HIDE;
+    ret = qobject_to(QDict, do_qmp_dispatch(false, cmd));
+    assert(ret && qdict_size(ret) == 0);
+    qobject_unref(ret);
+}
+
 /* test generated dealloc functions for generated types */
 static void test_dealloc_types(void)
 {
@@ -349,6 +379,8 @@ int main(int argc, char **argv)
     g_test_add_func("/qmp/dispatch_cmd_io", test_dispatch_cmd_io);
     g_test_add_func("/qmp/dispatch_cmd_success_response",
                     test_dispatch_cmd_success_response);
+    g_test_add_func("/qmp/dispatch_cmd_ret_deprecated",
+                    test_dispatch_cmd_ret_deprecated);
     g_test_add_func("/qmp/dealloc_types", test_dealloc_types);
     g_test_add_func("/qmp/dealloc_partial", test_dealloc_partial);