qapi: Implement deprecated-input=reject for QMP command arguments

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 deprecated parameter is removed, the error will change to

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

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20210318155519.1224118-11-armbru@redhat.com>

4 files changed, 25 insertions, 0 deletions

diff --git a/include/qapi/compat-policy.h b/include/qapi/compat-policy.h
index 94c8bbd790..1083f95122 100644
--- a/include/qapi/compat-policy.h
+++ b/include/qapi/compat-policy.h
@@ -18,6 +18,15 @@
 extern CompatPolicy compat_policy;
 
 /*
+ * 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 output visitor for @obj for use with QMP
  *
  * This is like qobject_output_visitor_new(), except it obeys the
diff --git a/include/qapi/qobject-input-visitor.h b/include/qapi/qobject-input-visitor.h
index 95985e25e5..8d69388810 100644
--- a/include/qapi/qobject-input-visitor.h
+++ b/include/qapi/qobject-input-visitor.h
@@ -15,6 +15,7 @@
 #ifndef QOBJECT_INPUT_VISITOR_H
 #define QOBJECT_INPUT_VISITOR_H
 
+#include "qapi/qapi-types-compat.h"
 #include "qapi/visitor.h"
 
 typedef struct QObjectInputVisitor QObjectInputVisitor;
@@ -58,6 +59,9 @@ typedef struct QObjectInputVisitor QObjectInputVisitor;
  */
 Visitor *qobject_input_visitor_new(QObject *obj);
 
+void qobject_input_visitor_set_policy(Visitor *v,
+                                      CompatPolicyInput deprecated);
+
 /*
  * 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 2d853255a3..3b950f6e3d 100644
--- a/include/qapi/visitor-impl.h
+++ b/include/qapi/visitor-impl.h
@@ -114,6 +114,9 @@ struct Visitor
     void (*optional)(Visitor *v, const char *name, bool *present);
 
     /* Optional */
+    bool (*deprecated_accept)(Visitor *v, const char *name, Error **errp);
+
+    /* Optional */
     bool (*deprecated)(Visitor *v, const char *name);
 
     /* Must be set */
diff --git a/include/qapi/visitor.h b/include/qapi/visitor.h
index 4d23b59853..b3c9ef7a81 100644
--- a/include/qapi/visitor.h
+++ b/include/qapi/visitor.h
@@ -460,6 +460,15 @@ void visit_end_alternate(Visitor *v, void **obj);
 bool visit_optional(Visitor *v, const char *name, bool *present);
 
 /*
+ * Should we reject deprecated member @name?
+ *
+ * @name must not be NULL.  This function is only useful between
+ * visit_start_struct() and visit_end_struct(), since only objects
+ * have deprecated members.
+ */
+bool visit_deprecated_accept(Visitor *v, const char *name, Error **errp);
+
+/*
  * Should we visit deprecated member @name?
  *
  * @name must not be NULL.  This function is only useful between