Make stream parser error when a non-empty object or array is used as key

Fixes #2463

src/jv_parse.c

@@ -246,6 +246,17 @@ static pfunc stream_token(struct jv_parser* p, char ch) {
   case '[':
     if (jv_is_valid(p->next))
       return "Expected a separator between values";
+    if (p->last_seen == JV_LAST_OPEN_OBJECT)
+      // Looks like {["foo"]}
+      return "Expected string key after '{', not '['";
+    if (p->last_seen == JV_LAST_COMMA) {
+      last = jv_array_get(jv_copy(p->path), p->stacklen - 1);
+      k = jv_get_kind(last);
+      jv_free(last);
+      if (k != JV_KIND_NUMBER)
+        // Looks like {"x":"y",["foo"]}
+        return "Expected string key after ',' in object, not '['";
+    }
     p->path = jv_array_append(p->path, jv_number(0)); // push
     p->last_seen = JV_LAST_OPEN_ARRAY;
     p->stacklen++;
@@ -254,6 +265,17 @@ static pfunc stream_token(struct jv_parser* p, char ch) {
   case '{':
     if (p->last_seen == JV_LAST_VALUE)
       return "Expected a separator between values";
+    if (p->last_seen == JV_LAST_OPEN_OBJECT)
+      // Looks like {{"foo":"bar"}}
+      return "Expected string key after '{', not '{'";
+    if (p->last_seen == JV_LAST_COMMA) {
+      last = jv_array_get(jv_copy(p->path), p->stacklen - 1);
+      k = jv_get_kind(last);
+      jv_free(last);
+      if (k != JV_KIND_NUMBER)
+        // Looks like {"x":"y",{"foo":"bar"}}
+        return "Expected string key after ',' in object, not '{'";
+    }
     // Push object key: null, since we don't know it yet
     p->path = jv_array_append(p->path, jv_null()); // push
     p->last_seen = JV_LAST_OPEN_OBJECT;

tests/shtest

@@ -222,6 +222,16 @@ fi
 echo '{"a":1,"b",' | $JQ --stream  > /dev/null 2> $d/err || true
 grep 'Objects must consist of key:value pairs' $d/err > /dev/null
 
+## Regression tests for issue #2463 assert when stream parse non-scalar object key
+echo '{{"a":"b"}}' | $JQ --stream > /dev/null 2> $d/err || true
+grep "Expected string key after '{', not '{'" $d/err > /dev/null
+echo '{"x":"y",{"a":"b"}}' | $JQ --stream > /dev/null 2> $d/err || true
+grep "Expected string key after ',' in object, not '{'" $d/err > /dev/null
+echo '{["a","b"]}' | $JQ --stream > /dev/null 2> $d/err || true
+grep "Expected string key after '{', not '\\['" $d/err > /dev/null
+echo '{"x":"y",["a","b"]}' | $JQ --stream > /dev/null 2> $d/err || true
+grep "Expected string key after ',' in object, not '\\['" $d/err > /dev/null
+
 ## Regression test for issue #2572 assert when using --jsonargs and invalid JSON
 $JQ -n --jsonargs null invalid && EC=$? || EC=$?
 if [ "$EC" -ne 2 ]; then