Nullable list of structs in json document

[zlesnr]

Howdy folks, I'm trying to create a "list" that is optional. Running vet on a json document that contains null where the cue spec defines a list gives me a type mismatch error that I'm confused about how to resolve. For example:

processes: [...#MatchedProcess]

In cue, while the json has

"processes": null

How can I have process either conform to the definition OR be null in order to get null to pass?

If I change the cue to look like so:

processes:       [...#MatchedProcess] | null

Then the error I receive is conflicting values null and [...string] (mismatched types null and list).

[mpvl]

This works for me:

processes: [...#MatchedProcess] | null
processes: null
#MatchedProcess: string

Can you describe the exact steps that lead to your error?

[zlesnr]

I'm unable to reproduce this this morning after getting it working yesterday.

❯ cat document_sample.json
{
  "discoveryManifest": {
    "processes": null
  }
}
❯ cat document.cue
discoveryManifest: #DiscoveryManifest

#DiscoveryManifest: {
        processes: [...#MatchedProcess] | null
}

#MatchedProcess: {
        command: string
}

Now cue vet document_sample.json document.cue executes without error.

I believe my confusion was that there were multiple errors in my document. The simple nullable string has been updated to entityGuid?: string, where the ? was missing before.

Is the ? an alternate syntax for |null, or is the |null syntax required for structs, while the ? is used on simple types? I also see references to |*null, but I'm unclear on the distinction.

[mpvl]

null has no special meaning in CUE. It is there mostly for JSON compatibility. The usage of null in JSON is so polluted that it really wasn't possible to assign any meaning to it consistently. So in the end, it is just another value at your disposal, just like true or false, but without assigning any meaning.

foo?: int is a shorthand for ["foo"]: int, but not for anything else.

[cueckoo]

This discussion has been migrated to cue-lang/cue#821.

For more details about CUE's migration to a new home, please see cue-lang/cue#1078.