Internal error with `cue eval -e`

[JensRantil]

What version of CUE are you using (cue version)?

$ cue version
cue version (devel)

CUE language version v0.15.1

Go version go1.25.4
      -buildmode exe
       -compiler gc
       -trimpath true
  DefaultGODEBUG containermaxprocs=0,decoratemappings=0,tlssha1=1,updatemaxprocs=0,x509sha256skid=0
     CGO_ENABLED 1
          GOARCH arm64
            GOOS darwin
         GOARM64 v8.0

Does this issue reproduce with the latest stable release?

Yes.

What did you do?

Two files:

match.json

{
  "pageProps": {
    "__APOLLO_STATE__": {
      "SecondProperty:12345": {
        "agentId": "767"
      }
    }
  },
  "__N_SSP": true
}

schema.cue

#Property: {
    type: string
    type: "FirstProperty" | "SecondProperty"
    
    agentId: string | null
}

pageProps: {
    "__APOLLO_STATE__": {
        [#FirstPropertyKey]: #SoldProperty
        [#SecondPropertyKey]: #SoldProperty
    }
    ...
}

#SoldProperty: {
    objectType: string
    agentId: string | null
    ...
}

#FirstPropertyKeyRegex: "^FirstProperty:.*"
#FirstPropertyKey: string
#FirstPropertyKey: =~ #FirstPropertyKeyRegex

#SecondPropertyKeyRegex: =~"^SecondProperty:.*"
#SecondPropertyKey: string
#SecondPropertyKey: =~ #SecondPropertyKeyRegex

_secondProperties: [#Property] | []
_secondProperties: [
    for k, v in pageProps["__APOLLO_STATE__"]
    if k =~ #SecondPropertyKeyRegex {
        {
            type: "SecondProperty"
            agentId: *v.agentId | null
        }
    }
]

_finalProperty: #Property
_finalProperty: _secondProperties[0]

_clean: #Property & {
    type: _finalProperty.type
    agentId: _finalProperty.agentId
}

I executed cue eval schema.cue match.json -e _clean.

What did you expect to see?

I expected to see the evaluated content of _clean written to standard out. Something like

{
    "type": "SecondProperty",
    "agentId": "767"
}

What did you see instead?

// ""cuelang.org/go/internal/core/export".Vertex: internal error
// Error: reference "FIRSTPROPERTYKEY" in label expression refers to field against which it would be matched (and 1 more errors)
//
// Profile:
// export.Profile{Simplify:true, Final:false, TakeDefaults:true, ShowOptional:false, ShowDefinitions:true, ShowHidden:false, ShowDocs:false, ShowAttributes:false, ShowErrors:false, SelfContained:false, Fragment:false, AddPackage:false, InlineImports:false, ExpandReferences:false}
//
// Value:
// {
//     type:    string & ("FirstProperty" | "SecondProperty") & _finalProperty.type
//     agentId: (string | null) & _finalProperty.agentId
// }
//
// You could file a bug with the above information at:
//     https://cuelang.org/issues/new?assignees=&labels=NeedsInvestigation&template=bug_report.md&title=.
//
_|_

Additional comments

Given that it refers me to submit an issue, I simply assume that this is a bug. I have simplified significantly and hope I have not made any typos. I would not be surprised if this bug(?) could be simplified even further.

[mvdan]

This definitely sounds like a bug we should fix.

You might be able to work around this bug by using cue export or cue vet rather than cue eval; we are likely going to deprecate or rework that command in the future.

[JensRantil]

👍 FYI, I simplified the input a bit more.

[JensRantil]

I suspect the issue is that there is no key in pageProps["__APOLLO_STATE__"] matching #FirstPropertyKey (ie. the regexp "^FirstProperty:.*"). In my case, I want corresponding keys matching it to have a value to fulfills #SoldProperty. If there are no keys that matches #FirstPropertyKey, no error should be triggered.

Given the above, I will avoid using the

pageProps: {
    "__APOLLO_STATE__": {
        [#FirstPropertyKey]: #SoldProperty
    }
    ...
}

pattern and instead iterate over the properties in pageProps["__APOLLO_STATE__"] using a comprehension and then match the value(s). I hope this workaround will suffice.