Extend open list avoiding conflicts

[cueckoo]

Originally opened by @b4nst in cuelang/cue#860

Is there a way to have this behavior working?

foo: {
  bar: "bar"
  l: [...int]
}

foo: l: l & [1, 2, ...]
foo: l: l & [3, ...]

{
    "foo": {
        "bar": "bar",
        "l": [
            1,
            2,
            3
        ]
    }
}

It's failing rightfully because 1 and 3 are conflicting. I've tried with list.Concat but since I want to use the same list I end up on a cycling error (also expected).

Currently my workaround is to use an embedded definition + field comprehension

foo: {
	bar: "bar"
	#l: {[string]: int}
	l: [ for k, v in #l {v}]
}
foo: #l: "1": 1
foo: #l: "2": 2
foo: #l: "3": 3

[cueckoo]

Original reply by @myitcv in cuelang/cue#860 (comment)

Do you find yourself in this situation there are multiple "sites" where you want to insert values?

If so, consider using hidden fields/definitions at each "site" and do something like:

package x

x: [
	for v in _a {v},
	for v in _b {v},
	for v in _c {v},
]

_a: [1, 2]
_b: [3]
_c: [8]

[cueckoo]

Original reply by @b4nst in cuelang/cue#860 (comment)

Indeed this workaround works too, thanks!

[cueckoo]

Original reply by @mpvl in cuelang/cue#860 (comment)

The idea is that this will be addressed with associative lists, See #165, but this is not implemented yet.

[cueckoo]

Original reply by @b4nst in cuelang/cue#860 (comment)

Thanks!