fix-carapace-examples

[xav-ie]

• fix(carapace example): update invariant

  Using previous invariant can sometimes be incorrect.

  See:
  https://github.com/carapace-sh/carapace/blob/09b28a62d9ce4acbade91bc967cee173454407c1/internal/common/message.go#L92-L114

---

With the new completers stuff that recently came out, I tried to first use these recipes, but found they were sometimes not working... especially for nix commands when it runs into db error:

> carapace "nix" nushell ...["nix" "run" "nixpkgs#"] | from json | select value
───┬───────────────
 # │     value
───┼───────────────
 0 │ "nixpkgs#ERR"
 1 │ "nixpkgs#_"
───┴───────────────

If we try and apply documented recipe to the first element, it does not work:

> let spans = ["nix" "run" "nixpkgs#"]
> carapace "nix" nushell ...["nix" "run" $last_span] | from json | get value | first
"nixpkgs#ERR"
> (carapace $spans.0 nushell ...$spans | from json | get value | first) == $"($spans | last)ERR"
false

This is because the value literally includes the chars " at beginning at end. I am not sure exactly how it happens, but we could fix the recipe in this instance by wrapping the check with quotes.

> (carapace $spans.0 nushell ...$spans | from json | get value | first) == $"\"($spans | last)ERR\""
true

--but this is not very good for things like the cargo -1 example, which is not output with quotes. A more reliable solution is to use the display column. According to this code:
https://github.com/carapace-sh/carapace/blob/09b28a62d9ce4acbade91bc967cee173454407c1/internal/common/message.go#L92-L114

the display column will always at least start-with "ERR".

Therefore, let us update this example to be more robust and use a better heuristic :).

---

p.s. I hope to also add docs/examples for the new completion methods and stuffs after this :)

[fdncred]

Thanks