Issue with filters and projections

[springcomp]

Most implementations seem to have the following issue:

Given the following JSON:

[
  {
    "stack": "",
    "branch": [
      "one/",
      "two/"
    ]
  },
  { "branch": ["three/", "four/"]}
]

The following expression yields an incorrect result:

• [?stack==''].branch[?starts_with(@, 'one')] -> invalid-type

In contrast, the following similar expression returns the expected result:

• [].branch[?starts_with(@, 'one')] -> [ [ "one/" ], [] ]

Please consider adding a compliance test and fixing the libraries.

[springcomp]

Looking more closely at the code, the root cause for this behaviour is that a filter [?…] bracket-specifier ends a projects, whereas a flatten [] bracket-specifier does not.

The Python parser has the following binding powers for its tokens:

        'flatten': 9,
        # Everything above stops a projection.
        'star': 20,
        'filter': 21,
        'dot': 40,

Nonetheless, the following compliance test in filters.json seems to contradict this behaviour:

{
  "given": {
    "reservations": [
      {
        "instances": [
          { "foo": 1, "bar": 2 },
          { "foo": 1, "bar": 3 },
          { "foo": 1, "bar": 2 },
          { "foo": 2, "bar": 1 }
        ]
      }
    ]
  },
  "cases": [
    {
      "expression": "reservations[*].instances[?bar==`1`]",
      "result": [ [ { "foo": "bar": 1 } ] ]
    }
  ]
}