ra: fix subkey_to_object to support direct array access

Record Accessor API couldn't handle direct array access
patterns like $array[0]. This fix changes the condition that
checks if a lookup succeeded by replacing !found with matched == 0,
which properly tracks array element access.

Added test cases to verify array access works:
- Direct array access ($array[0])
- Nested array access ($matrix[1][2])
- Mixed array and map access ($records[1]['name'])
- Access with out-of-bounds indices
- Nonexistent key access
- Type mismatch handling
- Nested path failures

Fixes #9958

Signed-off-by: Jorge Niedbalski <[email protected]>

Author: niedbalski

src/flb_ra_key.c

@@ -121,12 +121,11 @@ static int msgpack_object_strcmp(msgpack_object o, char *str, int len)
 
 /* Lookup perfect match of sub-keys and map content */
 static int subkey_to_object(msgpack_object *map, struct mk_list *subkeys,
-                            msgpack_object **out_key, msgpack_object **out_val)
+                           msgpack_object **out_key, msgpack_object **out_val)
 {
     int i = 0;
     int levels;
     int matched = 0;
-    msgpack_object *found = NULL;
     msgpack_object *key = NULL;
     msgpack_object *val = NULL;
     msgpack_object cur;
@@ -136,6 +135,11 @@ static int subkey_to_object(msgpack_object *map, struct mk_list *subkeys,
     /* Expected number of map levels in the map */
     levels = mk_list_size(subkeys);
 
+    /* Early return if no subkeys */
+    if (levels == 0) {
+        return -1;
+    }
+
     cur = *map;
 
     mk_list_foreach(head, subkeys) {
@@ -150,40 +154,41 @@ static int subkey_to_object(msgpack_object *map, struct mk_list *subkeys,
             }
 
             /* Index limit and ensure no overflow */
-            if (entry->array_id == INT_MAX ||
-                cur.via.array.size < entry->array_id + 1) {
+            if (entry->array_id == INT_MAX || entry->array_id >= cur.via.array.size) {
                 return -1;
             }
 
             val = &cur.via.array.ptr[entry->array_id];
             cur = *val;
             key = NULL; /* fill NULL since the type is array. */
-            goto next;
+            matched++;
+
+            if (levels == matched) {
+                break;
+            }
+
+            continue;
         }
 
+        /* Handle map objects */
         if (cur.type != MSGPACK_OBJECT_MAP) {
             break;
         }
 
         i = ra_key_val_id(entry->str, cur);
         if (i == -1) {
-            found = NULL;
-            continue;
+            continue;  /* Try next entry */
         }
 
         key = &cur.via.map.ptr[i].key;
         val = &cur.via.map.ptr[i].val;
 
         /* A bit obvious, but it's better to validate data type */
         if (key->type != MSGPACK_OBJECT_STR) {
-            found = NULL;
-            continue;
+            continue;  /* Try next entry */
         }
 
-        found = key;
-        cur = cur.via.map.ptr[i].val;
-
-    next:
+        cur = *val;
         matched++;
 
         if (levels == matched) {
@@ -192,12 +197,12 @@ static int subkey_to_object(msgpack_object *map, struct mk_list *subkeys,
     }
 
     /* No matches */
-    if (!found || (matched > 0 && levels != matched)) {
+    if (matched == 0 || (matched > 0 && levels != matched)) {
         return -1;
     }
 
-    *out_key = (msgpack_object *) key;
-    *out_val = (msgpack_object *) val;
+    *out_key = key;
+    *out_val = val;
 
     return 0;
 }