"Child in specific slot" selector?

[papandreou]

Hi, I'm thinking about using esquery for matching some pretty deeply nested constructs. I need to differentiate between eg. the object and property of a MemberExpression, so I cannot use the child selector, as it will match a child in either position:

const q = esquery.parse('MemberExpression > Identifier[name=foo]');
const ast = require('acorn').parse("foo.foo()")
console.log(esquery.match(ast, q));
[ Node { type: 'Identifier', start: 0, end: 3, name: 'foo' },
  Node { type: 'Identifier', start: 4, end: 7, name: 'foo' } ]

I know that I drop into "attribute mode" and achieve what I need using a query like:

MemberExpression[property.name=foo]

... but since the asts I need to match are much deeper than that, it would be really awkward to have to spell out the rest of the subtree like that with lots of repeated [property.foo.bar=123][property.foo.quux=abc]. It would be much nicer if I could use something like the > selector to cover the nesting aspects.

Am I overlooking a nice way to achieve that?

[papandreou]

Oh, turns out this is exactly what the "field" selector is supposed to do. I didn't understand that when I first tried because the subject indicator bug (#60) caused me to get the wrong nodes. I tried switching to jupenur's fork, and now everything seems to work as described.