keyval: Support lists

Additionally permit non-negative integers as key components.  A
dictionary's keys must either be all integers or none.  If all keys
are integers, convert the dictionary to a list.  The set of keys must
be [0,N].

Examples:

* list.1=goner,list.0=null,list.1=eins,list.2=zwei
  is equivalent to JSON [ "null", "eins", "zwei" ]

* a.b.c=1,a.b.0=2
  is inconsistent: a.b.c clashes with a.b.0

* list.0=null,list.2=eins,list.2=zwei
  has a hole: list.1 is missing

Similar design flaw as for objects: there is no way to denote an empty
list.  While interpreting "key absent" as empty list seems natural
(removing a list member from the input string works when there are
multiple ones, so why not when there's just one), it doesn't work:
"key absent" already means "optional list absent", which isn't the
same as "empty list present".

Update the keyval object visitor to use this a.0 syntax in error
messages rather than the usual a[0].

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <1488317230-26248-25-git-send-email-armbru@redhat.com>
[Off-by-one fix squashed in, as per Kevin's review]
Reviewed-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 5 insertions, 1 deletions

diff --git a/qapi/qobject-input-visitor.c b/qapi/qobject-input-visitor.c
index b9acd86f4f..865e948ac0 100644
--- a/qapi/qobject-input-visitor.c
+++ b/qapi/qobject-input-visitor.c
@@ -41,6 +41,7 @@ struct QObjectInputVisitor {
 
     /* Root of visit at visitor creation. */
     QObject *root;
+    bool keyval;                /* Assume @root made with keyval_parse() */
 
     /* Stack of objects being visited (all entries will be either
      * QDict or QList). */
@@ -73,7 +74,9 @@ static const char *full_name_nth(QObjectInputVisitor *qiv, const char *name,
             g_string_prepend(qiv->errname, name ?: "<anonymous>");
             g_string_prepend_c(qiv->errname, '.');
         } else {
-            snprintf(buf, sizeof(buf), "[%u]", so->index);
+            snprintf(buf, sizeof(buf),
+                     qiv->keyval ? ".%u" : "[%u]",
+                     so->index);
             g_string_prepend(qiv->errname, buf);
         }
         name = so->name;
@@ -673,6 +676,7 @@ Visitor *qobject_input_visitor_new_keyval(QObject *obj)
     v->visitor.type_any = qobject_input_type_any;
     v->visitor.type_null = qobject_input_type_null;
     v->visitor.type_size = qobject_input_type_size_keyval;
+    v->keyval = true;
 
     return &v->visitor;
 }