[PATCH v4 33/34] qapi: Implement deprecated-input=reject for QMP command arguments

[Markus Armbruster <armbru@redhat.com>]

This policy rejects deprecated input, and thus permits "testing the
future".  Implement it for QMP command arguments: reject commands with
deprecated ones.  Example: when QEMU is run with -compat
deprecated-input=reject, then

    {"execute": "eject", "arguments": {"device": "cd"}}

fails like this

    {"error": {"class": "GenericError", "desc": "Deprecated parameter 'device' disabled by policy"}}

When the argument is removed, the error will change to

    {"error": {"class": "GenericError", "desc": "Parameter 'device' is unexpected"}}

Signed-off-by: Markus Armbruster <armbru@redhat.com>
---
 include/qapi/qobject-input-visitor.h |  9 +++++++++
 include/qapi/visitor-impl.h          |  2 +-
 include/qapi/visitor.h               |  2 +-
 qapi/qapi-visit-core.c               |  4 ++--
 qapi/qobject-input-visitor.c         | 28 ++++++++++++++++++++++++++++
 qapi/qobject-output-visitor.c        |  3 ++-
 tests/test-qmp-cmds.c                | 25 +++++++++++++++++++++++++
 scripts/qapi/commands.py             |  2 +-
 scripts/qapi/visit.py                | 10 ++++++----
 9 files changed, 75 insertions(+), 10 deletions(-)

diff --git a/include/qapi/qobject-input-visitor.h b/include/qapi/qobject-input-visitor.h
index 95985e25e5..cbc54de4ac 100644
--- a/include/qapi/qobject-input-visitor.h
+++ b/include/qapi/qobject-input-visitor.h
@@ -58,6 +58,15 @@ typedef struct QObjectInputVisitor QObjectInputVisitor;
  */
 Visitor *qobject_input_visitor_new(QObject *obj);
 
+/*
+ * Create a QObject input visitor for @obj for use with QMP
+ *
+ * This is like qobject_input_visitor_new(), except it obeys the
+ * policy for handling deprecated management interfaces set with
+ * -compat.
+ */
+Visitor *qobject_input_visitor_new_qmp(QObject *obj);
+
 /*
  * Create a QObject input visitor for @obj for use with keyval_parse()
  *
diff --git a/include/qapi/visitor-impl.h b/include/qapi/visitor-impl.h
index a6b26b7a5b..ccc159a0d2 100644
--- a/include/qapi/visitor-impl.h
+++ b/include/qapi/visitor-impl.h
@@ -111,7 +111,7 @@ struct Visitor
     void (*optional)(Visitor *v, const char *name, bool *present);
 
     /* Optional */
-    bool (*deprecated)(Visitor *v, const char *name);
+    bool (*deprecated)(Visitor *v, const char *name, Error **errp);
 
     /* Must be set */
     VisitorType type;
diff --git a/include/qapi/visitor.h b/include/qapi/visitor.h
index c89d51b2a4..2a3c4d0407 100644
--- a/include/qapi/visitor.h
+++ b/include/qapi/visitor.h
@@ -456,7 +456,7 @@ bool visit_optional(Visitor *v, const char *name, bool *present);
  * visit_start_struct() and visit_end_struct(), since only objects
  * have deprecated members.
  */
-bool visit_deprecated(Visitor *v, const char *name);
+bool visit_deprecated(Visitor *v, const char *name, Error **errp);
 
 /*
  * Visit an enum value.
diff --git a/qapi/qapi-visit-core.c b/qapi/qapi-visit-core.c
index 501b3ccdef..71e4978a6f 100644
--- a/qapi/qapi-visit-core.c
+++ b/qapi/qapi-visit-core.c
@@ -137,11 +137,11 @@ bool visit_optional(Visitor *v, const char *name, bool *present)
     return *present;
 }
 
-bool visit_deprecated(Visitor *v, const char *name)
+bool visit_deprecated(Visitor *v, const char *name, Error **errp)
 {
     trace_visit_deprecated(v, name);
     if (v->deprecated) {
-        return v->deprecated(v, name);
+        return v->deprecated(v, name, errp);
     }
     return true;
 }
diff --git a/qapi/qobject-input-visitor.c b/qapi/qobject-input-visitor.c
index 32236cbcb1..6ea93f5a7a 100644
--- a/qapi/qobject-input-visitor.c
+++ b/qapi/qobject-input-visitor.c
@@ -14,6 +14,7 @@
 
 #include "qemu/osdep.h"
 #include <math.h>
+#include "qapi/compat-policy.h"
 #include "qapi/error.h"
 #include "qapi/qobject-input-visitor.h"
 #include "qapi/visitor-impl.h"
@@ -43,6 +44,7 @@ typedef struct StackObject {
 
 struct QObjectInputVisitor {
     Visitor visitor;
+    CompatPolicyInput deprecated_policy;
 
     /* Root of visit at visitor creation. */
     QObject *root;
@@ -640,6 +642,23 @@ static void qobject_input_optional(Visitor *v, const char *name, bool *present)
     *present = true;
 }
 
+static bool qobject_input_deprecated(Visitor *v, const char *name,
+                                     Error **errp)
+{
+    QObjectInputVisitor *qiv = to_qiv(v);
+
+    switch (qiv->deprecated_policy) {
+    case COMPAT_POLICY_INPUT_ACCEPT:
+        return true;
+    case COMPAT_POLICY_INPUT_REJECT:
+        error_setg(errp, "Deprecated parameter '%s' disabled by policy",
+                   name);
+        return false;
+    default:
+        abort();
+    }
+}
+
 static void qobject_input_free(Visitor *v)
 {
     QObjectInputVisitor *qiv = to_qiv(v);
@@ -674,6 +693,7 @@ static QObjectInputVisitor *qobject_input_visitor_base_new(QObject *obj)
     v->visitor.end_list = qobject_input_end_list;
     v->visitor.start_alternate = qobject_input_start_alternate;
     v->visitor.optional = qobject_input_optional;
+    v->visitor.deprecated = qobject_input_deprecated;
     v->visitor.free = qobject_input_free;
 
     v->root = qobject_ref(obj);
@@ -696,6 +716,14 @@ Visitor *qobject_input_visitor_new(QObject *obj)
     return &v->visitor;
 }
 
+Visitor *qobject_input_visitor_new_qmp(QObject *obj)
+{
+    QObjectInputVisitor *v = to_qiv(qobject_input_visitor_new(obj));
+
+    v->deprecated_policy = compat_policy.deprecated_input;
+    return &v->visitor;
+}
+
 Visitor *qobject_input_visitor_new_keyval(QObject *obj)
 {
     QObjectInputVisitor *v = qobject_input_visitor_base_new(obj);
diff --git a/qapi/qobject-output-visitor.c b/qapi/qobject-output-visitor.c
index 84cee17596..73983ca5cc 100644
--- a/qapi/qobject-output-visitor.c
+++ b/qapi/qobject-output-visitor.c
@@ -201,7 +201,8 @@ static void qobject_output_type_null(Visitor *v, const char *name,
     qobject_output_add(qov, name, qnull());
 }
 
-static bool qobject_output_deprecated(Visitor *v, const char *name)
+static bool qobject_output_deprecated(Visitor *v, const char *name,
+                                      Error **errp)
 {
     QObjectOutputVisitor *qov = to_qov(v);
 
diff --git a/tests/test-qmp-cmds.c b/tests/test-qmp-cmds.c
index a2099fee7d..4ca658acf9 100644
--- a/tests/test-qmp-cmds.c
+++ b/tests/test-qmp-cmds.c
@@ -299,6 +299,29 @@ static void test_dispatch_cmd_deprecated(void)
     do_qmp_dispatch_error(false, ERROR_CLASS_COMMAND_NOT_FOUND, cmd);
 }
 
+static void test_dispatch_cmd_arg_deprecated(void)
+{
+    const char *cmd = "{ 'execute': 'test-features0',"
+        " 'arguments': { 'fs1': { 'foo': 42 } } }";
+    QDict *ret;
+
+    memset(&compat_policy, 0, sizeof(compat_policy));
+
+    /* accept */
+    ret = qobject_to(QDict, do_qmp_dispatch(false, cmd));
+    assert(ret && qdict_size(ret) == 1);
+    qobject_unref(ret);
+
+    compat_policy.has_deprecated_input = true;
+    compat_policy.deprecated_input = COMPAT_POLICY_INPUT_ACCEPT;
+    ret = qobject_to(QDict, do_qmp_dispatch(false, cmd));
+    assert(ret && qdict_size(ret) == 1);
+    qobject_unref(ret);
+
+    compat_policy.deprecated_input = COMPAT_POLICY_INPUT_REJECT;
+    do_qmp_dispatch_error(false, ERROR_CLASS_GENERIC_ERROR, cmd);
+}
+
 static void test_dispatch_cmd_ret_deprecated(void)
 {
     const char *cmd = "{ 'execute': 'test-features0' }";
@@ -399,6 +422,8 @@ int main(int argc, char **argv)
                     test_dispatch_cmd_success_response);
     g_test_add_func("/qmp/dispatch_cmd_deprecated",
                     test_dispatch_cmd_deprecated);
+    g_test_add_func("/qmp/dispatch_cmd_arg_deprecated",
+                    test_dispatch_cmd_arg_deprecated);
     g_test_add_func("/qmp/dispatch_cmd_ret_deprecated",
                     test_dispatch_cmd_ret_deprecated);
     g_test_add_func("/qmp/dealloc_types", test_dealloc_types);
diff --git a/scripts/qapi/commands.py b/scripts/qapi/commands.py
index f628bbf144..3fb4ed42ed 100644
--- a/scripts/qapi/commands.py
+++ b/scripts/qapi/commands.py
@@ -132,7 +132,7 @@ def gen_marshal(name, arg_type, boxed, ret_type):
         push_indent()
 
     ret += mcgen('''
-    v = qobject_input_visitor_new(QOBJECT(args));
+    v = qobject_input_visitor_new_qmp(QOBJECT(args));
     visit_start_struct(v, NULL, NULL, 0, &err);
     if (err) {
         goto out;
diff --git a/scripts/qapi/visit.py b/scripts/qapi/visit.py
index 21df3abed2..9119eb015b 100644
--- a/scripts/qapi/visit.py
+++ b/scripts/qapi/visit.py
@@ -66,15 +66,12 @@ void visit_type_%(c_name)s_members(Visitor *v, %(c_name)s *obj, Error **errp)
             push_indent()
         if deprecated:
             ret += mcgen('''
-    if (visit_deprecated(v, "%(name)s")) {
+    if (visit_deprecated(v, "%(name)s", &err)) {
 ''',
                          name=memb.name)
             push_indent()
         ret += mcgen('''
     visit_type_%(c_type)s(v, "%(name)s", &obj->%(c_name)s, &err);
-    if (err) {
-        goto out;
-    }
 ''',
                      c_type=memb.type.c_name(), name=memb.name,
                      c_name=c_name(memb.name))
@@ -82,6 +79,11 @@ void visit_type_%(c_name)s_members(Visitor *v, %(c_name)s *obj, Error **errp)
             pop_indent()
             ret += mcgen('''
     }
+''')
+        ret += mcgen('''
+    if (err) {
+        goto out;
+    }
 ''')
         if memb.optional:
             pop_indent()
-- 
2.21.1