Searching for a literal * with $['*'] yields the following unexpected behavior:

JSONPath({json: {'*': 'star', 'rest': 'rest', 'foo': 'bar'}, path: "$['*']"})
//=> [ 'star' ]
JSONPath({json: {'rest': 'rest', 'foo': 'bar'}, path: "$['*']"})
//=> [ 'rest', 'bar' ]

It's possible to work around this with $[?(@property === '*')], but this isn't usable in more complex queries, such as $[?(@property === '*'), rest]