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To solve a problem with node locations generated when using the non-standard keys selector (~), we need a way to conditionally select an object's keys, which could also be useful aside from creating valid node locations.

Whereas the standard filter selector ([? <expression>]) selects values from an array or object when the expression evaluates to true, the keys filter selector would select keys instead of values. Syntax for this could be [?~ <expression>] or [~? <expression>].

Alternatively (or additionally), we could implement a key selector ("key" singular), which selects the key if it exists. Syntax could be $.obj.~name or $.obj[~'name'] or $.obj[~"name"]. Without this we could use the proposed keys filter selector like this:

[~? # == 'name']

But that would not be a singular query and the key selector would.

The *lazyResolve method of SliceSelector uses the non-lazy private slice method. We should add a generator version of slice, which should be more memory efficient when used on large arrays with large slice ranges.

Considering our abstract class JSONPathSelector, and the absence of a JSONPathSegment class, we are currently blurring the lines between segments and selectors.

We should refactor to follow the JSONPath model described in RFC 9535 by implementing a JSONPathSegment class, where all JSONPathSelector instances belong to a segment, even shorthand selectors. In turn, a JSONPath expression (currently JSONPath and should be JSONPathQuery or JSONPathExpression to match terminology from RFC 9535) should be made up of segments only.

This diagram illustrates what we want.