qapi: Make input visitors detect unvisited list tails

Fix the design flaw demonstrated in the previous commit: new method
check_list() lets input visitors report that unvisited input remains
for a list, exactly like check_struct() lets them report that
unvisited input remains for a struct or union.

Implement the method for the qobject input visitor (straightforward),
and the string input visitor (less so, due to the magic list syntax
there).  The opts visitor's list magic is even more impenetrable, and
all I can do there today is a stub with a FIXME comment.  No worse
than before.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <1488544368-30622-26-git-send-email-armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>

1 files changed, 31 insertions, 6 deletions

diff --git a/qapi/qobject-input-visitor.c b/qapi/qobject-input-visitor.c
index eafcdf4625..34065ba7dd 100644
--- a/qapi/qobject-input-visitor.c
+++ b/qapi/qobject-input-visitor.c
@@ -51,7 +51,8 @@ static QObjectInputVisitor *to_qiv(Visitor *v)
     return container_of(v, QObjectInputVisitor, visitor);
 }
 
-static const char *full_name(QObjectInputVisitor *qiv, const char *name)
+static const char *full_name_nth(QObjectInputVisitor *qiv, const char *name,
+                                 int n)
 {
     StackObject *so;
     char buf[32];
@@ -63,8 +64,10 @@ static const char *full_name(QObjectInputVisitor *qiv, const char *name)
     }
 
     QSLIST_FOREACH(so , &qiv->stack, node) {
-        if (qobject_type(so->obj) == QTYPE_QDICT) {
-            g_string_prepend(qiv->errname, name);
+        if (n) {
+            n--;
+        } else if (qobject_type(so->obj) == QTYPE_QDICT) {
+            g_string_prepend(qiv->errname, name ?: "<anonymous>");
             g_string_prepend_c(qiv->errname, '.');
         } else {
             snprintf(buf, sizeof(buf), "[%u]", so->index);
@@ -72,18 +75,24 @@ static const char *full_name(QObjectInputVisitor *qiv, const char *name)
         }
         name = so->name;
     }
+    assert(!n);
 
     if (name) {
         g_string_prepend(qiv->errname, name);
     } else if (qiv->errname->str[0] == '.') {
         g_string_erase(qiv->errname, 0, 1);
-    } else {
+    } else if (!qiv->errname->str[0]) {
         return "<anonymous>";
     }
 
     return qiv->errname->str;
 }
 
+static const char *full_name(QObjectInputVisitor *qiv, const char *name)
+{
+    return full_name_nth(qiv, name, 0);
+}
+
 static QObject *qobject_input_try_get_object(QObjectInputVisitor *qiv,
                                              const char *name,
                                              bool consume)
@@ -260,15 +269,30 @@ static GenericList *qobject_input_next_list(Visitor *v, GenericList *tail,
                                             size_t size)
 {
     QObjectInputVisitor *qiv = to_qiv(v);
-    StackObject *so = QSLIST_FIRST(&qiv->stack);
+    StackObject *tos = QSLIST_FIRST(&qiv->stack);
+
+    assert(tos && tos->obj && qobject_type(tos->obj) == QTYPE_QLIST);
 
-    if (!so->entry) {
+    if (!tos->entry) {
         return NULL;
     }
     tail->next = g_malloc0(size);
     return tail->next;
 }
 
+static void qobject_input_check_list(Visitor *v, Error **errp)
+{
+    QObjectInputVisitor *qiv = to_qiv(v);
+    StackObject *tos = QSLIST_FIRST(&qiv->stack);
+
+    assert(tos && tos->obj && qobject_type(tos->obj) == QTYPE_QLIST);
+
+    if (tos->entry) {
+        error_setg(errp, "Only %u list elements expected in %s",
+                   tos->index + 1, full_name_nth(qiv, NULL, 1));
+    }
+}
+
 
 static void qobject_input_start_alternate(Visitor *v, const char *name,
                                           GenericAlternate **obj, size_t size,
@@ -471,6 +495,7 @@ Visitor *qobject_input_visitor_new(QObject *obj)
     v->visitor.end_struct = qobject_input_pop;
     v->visitor.start_list = qobject_input_start_list;
     v->visitor.next_list = qobject_input_next_list;
+    v->visitor.check_list = qobject_input_check_list;
     v->visitor.end_list = qobject_input_pop;
     v->visitor.start_alternate = qobject_input_start_alternate;
     v->visitor.type_int64 = qobject_input_type_int64;