Conditionals in lists

[cueckoo]

Originally opened by @eonpatapon in cuelang/cue#713

It is now possible to include multiple comprehensions and if conditions in lists:

a: true

l: [
	if a {
		"foo"
	},
	"foobar",
]

Returns:

a: true
l: ["foo", "foobar"]

However it doesn't seem possible to include multiple items in the if clause. This doesn't work:

a: true

l: [
	if a {
		"foo",
		"bar",
	},
	"foobar",
]

Returns:

 cue eval x.cue
l.0: conflicting values "bar" and "foo":

Is there a workaround or plans to make this work ?

[cueckoo]

Original reply by @myitcv in cuelang/cue#713 (comment)

I'll leave @mpvl to comment on whether anything like this would ever make sense.

But for now you can:

package x

a: true

l: [
	for _, v in ["foo", "bar"] if a {
		v
	},
	"foobar",
]

[cueckoo]

Original reply by @mpvl in cuelang/cue#713 (comment)

This is the correct answer. The other thing indeed would never make sense, as { "foo", "bar" } inherently means { "foo" & "bar" } a per the embedding rules (and it would be weird to make an exception in this case).