Issues with filters and projections

[springcomp]

I’m currently assessing the following behaviour.

Given the following JSON:

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

The following expression yields the following result:

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

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

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

The tension is that both expressions are similart in construct and should, IMHO, return the same result.
Either a valid result or the same error.

As I’m trying to iterate on some implementations, and fix some issues, I would like to include a fix for this issue, either way.

What do you think ?

[springcomp]

The more I think of this, the more I’m convinced that it is to be entirely expected for the filter expression to return an error.
I also think the second expression is currently incorrectly returning a result whereas it should fail with the same error.

Indeed the starts_with() function is designed to operate on input of type string.
Both the [].branch and [?stack==''].branch expressions, however, return an array that contains arrays.
So it makes sense to receive an error when each array item is projected onto the starts_with() function.

What do you think ?