[RFC PATCH 16/19] qapi: Implement -compat deprecated-input=reject for commands

[Markus Armbruster <armbru@redhat.com>]

This policy makes deprecated commands fail like this:

    ---> {"execute": "query-cpus"}
    <--- {"error": {"class": "CommandNotFound", "desc": "Deprecated command query-cpus disabled by policy"}}

When the command is removed, the error will change to

    <--- {"error": {"class": "CommandNotFound", "desc": "The command query-cpus has not been found"}}

The policy thus permits "testing the future".

Signed-off-by: Markus Armbruster <armbru@redhat.com>
---
 qapi/common.json            |  4 ++--
 include/qapi/qmp/dispatch.h |  1 +
 qapi/qmp-dispatch.c         | 13 +++++++++++++
 tests/test-qmp-cmds.c       | 23 +++++++++++++++++++++++
 qemu-options.hx             |  4 +++-
 scripts/qapi/commands.py    | 10 +++++++---
 6 files changed, 49 insertions(+), 6 deletions(-)

diff --git a/qapi/common.json b/qapi/common.json
index 9fc3e6400c..3e9d12c90f 100644
--- a/qapi/common.json
+++ b/qapi/common.json
@@ -151,7 +151,7 @@
 # Policy for handling "funny" input.
 #
 # @accept: Accept silently
-# TODO @reject: Reject with an error
+# @reject: Reject with an error
 # TODO @crash: abort() the process
 #
 # FIXME Guidance on intended use.
@@ -159,7 +159,7 @@
 # Since: 4.2
 ##
 { 'enum': 'CompatPolicyInput',
-  'data': [ 'accept' ] }
+  'data': [ 'accept', 'reject' ] }
 
 ##
 # @CompatPolicyOutput:
diff --git a/include/qapi/qmp/dispatch.h b/include/qapi/qmp/dispatch.h
index 9aa426a398..ef256f2bb7 100644
--- a/include/qapi/qmp/dispatch.h
+++ b/include/qapi/qmp/dispatch.h
@@ -24,6 +24,7 @@ typedef enum QmpCommandOptions
     QCO_NO_SUCCESS_RESP       =  (1U << 0),
     QCO_ALLOW_OOB             =  (1U << 1),
     QCO_ALLOW_PRECONFIG       =  (1U << 2),
+    QCO_DEPRECATED            =  (1U << 3),
 } QmpCommandOptions;
 
 typedef struct QmpCommand
diff --git a/qapi/qmp-dispatch.c b/qapi/qmp-dispatch.c
index 8fe59cf54d..b079db85d2 100644
--- a/qapi/qmp-dispatch.c
+++ b/qapi/qmp-dispatch.c
@@ -132,6 +132,19 @@ QDict *qmp_dispatch(QmpCommandList *cmds, QObject *request,
                   "The command %s has not been found", command);
         goto out;
     }
+    if (cmd->options & QCO_DEPRECATED) {
+        switch (qapi_compat_policy.deprecated_input) {
+        case COMPAT_POLICY_INPUT_ACCEPT:
+            break;
+        case COMPAT_POLICY_INPUT_REJECT:
+            error_set(&err, ERROR_CLASS_COMMAND_NOT_FOUND,
+                      "Deprecated command %s disabled by policy",
+                      command);
+            goto out;
+        default:
+            abort();
+        }
+    }
     if (!cmd->enabled) {
         error_set(&err, ERROR_CLASS_COMMAND_NOT_FOUND,
                   "The command %s has been disabled for this instance",
diff --git a/tests/test-qmp-cmds.c b/tests/test-qmp-cmds.c
index cf4fa1a091..005ea24a27 100644
--- a/tests/test-qmp-cmds.c
+++ b/tests/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"
@@ -235,6 +236,26 @@ static void test_dispatch_cmd_success_response(void)
     qobject_unref(req);
 }
 
+static void test_dispatch_cmd_deprecated(void)
+{
+    const char *cmd = "{ 'execute': 'test-command-features1' }";
+    QDict *ret;
+
+    /* accept */
+    ret = qobject_to(QDict, do_qmp_dispatch(false, cmd));
+    assert(ret && qdict_size(ret) == 0);
+    qobject_unref(ret);
+
+    qapi_compat_policy.has_deprecated_input = true;
+    qapi_compat_policy.deprecated_input = COMPAT_POLICY_INPUT_ACCEPT;
+    ret = qobject_to(QDict, do_qmp_dispatch(false, cmd));
+    assert(ret && qdict_size(ret) == 0);
+    qobject_unref(ret);
+
+    qapi_compat_policy.deprecated_input = COMPAT_POLICY_INPUT_REJECT;
+    do_qmp_dispatch_error(false, ERROR_CLASS_COMMAND_NOT_FOUND, cmd);
+}
+
 /* test commands that involve both input parameters and return values */
 static void test_dispatch_cmd_io(void)
 {
@@ -344,6 +365,8 @@ 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_deprecated",
+                    test_dispatch_cmd_deprecated);
     g_test_add_func("/qmp/dealloc_types", test_dealloc_types);
     g_test_add_func("/qmp/dealloc_partial", test_dealloc_partial);
 
diff --git a/qemu-options.hx b/qemu-options.hx
index c43f768a15..f107a57c81 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][,deprecated-output=accept]\n"
+    "-compat [deprecated-input=accept|reject][,deprecated-output=accept]\n"
     "                Policy for handling deprecated management interfaces\n",
     QEMU_ARCH_ALL)
 STEXI
@@ -3331,6 +3331,8 @@ Set policy for handling deprecated management interfaces:
 @table @option
 @item deprecated-input=accept (default)
 Accept deprecated commands
+@item deprecated-input=reject
+Reject deprecated commands
 @item deprecated-output=accept (default)
 Emit deprecated events
 @end table
diff --git a/scripts/qapi/commands.py b/scripts/qapi/commands.py
index 11e9a6c095..df2a132915 100644
--- a/scripts/qapi/commands.py
+++ b/scripts/qapi/commands.py
@@ -194,9 +194,13 @@ out:
     return ret
 
 
-def gen_register_command(name, success_response, allow_oob, allow_preconfig):
+def gen_register_command(name, features,
+                         success_response, allow_oob, allow_preconfig):
     options = []
 
+    if 'deprecated' in [f.name for f in features]:
+        options += ['QCO_DEPRECATED']
+
     if not success_response:
         options += ['QCO_NO_SUCCESS_RESP']
     if allow_oob:
@@ -295,8 +299,8 @@ void %(c_prefix)sqmp_init_marshal(QmpCommandList *cmds);
             self._genh.add(gen_command_decl(name, arg_type, boxed, ret_type))
             self._genh.add(gen_marshal_decl(name))
             self._genc.add(gen_marshal(name, arg_type, boxed, ret_type))
-            self._regy.add(gen_register_command(name, success_response,
-                                                allow_oob, allow_preconfig))
+            self._regy.add(gen_register_command(
+                name, features, success_response, allow_oob, allow_preconfig))
 
 
 def gen_commands(schema, output_dir, prefix):
-- 
2.21.0