JSON parser decodes escapes in selectors

[glyn]

@akshaymankar raised the following issue:

Hi, I finally found time to work on [making jsonpath-hs pass the CTS]. I think the cts.json needs to double escape all the tests [with] selectors which encode characters using the \u notation. Otherwise the JSON parser which parses the test already decodes them giving no chance to the jsonpath parser.

[gregsdennis]

Are we talking about updating

{
  "name": "name selector, double quotes, embedded U+0000",
  "selector": "$[\"\u0000\"]",
  "invalid_selector": true
}

to

{
  "name": "name selector, double quotes, embedded U+0000",
  "selector": "$[\"\\u0000\"]",
  "invalid_selector": true
}

That means the un-JSON'd path is $["\u0000"] instead of $[""] (which isn't rendered here but should have a 0-char in the string). Do we want to test both, maybe?

These tests, specifically, are supposed to be invalid as we required those chars to be escaped, but I don't see tests where we check the results of paths that do properly escape them.

[glyn]

Yes, I think we need to test both those situations. If we don't already, we should also test the use of a Unicode escape in a query to represent a character that is not escaped in the JSON.