A case with data query

[roman-mazur]

Hello,

I'm experimenting with the following sample where I query some data and then use the query result in some transformation.

https://cuelang.org/play/?id=6qSfDcl8A2m#cue@export@cue

#Data: {x: string, y: string}

All: [...#Data]
All: [{x: "a", y: "b"}, {x: "c", y: "d"}]

#Get: {
  #filter: string
  
  _#search: [for d in All if d.x == #filter {d}]
  _#valid: len(_#search) & 1
  
  _#search[0]
}

query: #Get & { #filter: "a" }

#Stringify: {
  #input: #Data
  "x=\(#input.x)  y=\(#input.y)"
}

str: {#Stringify, #input: query}

From my point of view this should work, but I'm getting an error. Try commenting out the line with str: - you will see that the query is successful, it resolves to a concrete value. However, when I refer to this result from a different place, it fails with a mysterious error.

I would appreciate somebody's look to understand if it should be submitted as a bug.

[roman-mazur]

If I change #Get to not use the embedding, but expose a separate field, it works.

#Get: {
  #filter: string
  
  _#search: [for d in All if d.x == #filter {d}]
  _#valid: len(_#search) & 1
  
  result: _#search[0]
}

query: (#Get & { #filter: "a" }).result

https://cuelang.org/play/?id=Go4fW9WFF2m#cue@export@cue

[verdverm]

Another variation: https://cuelang.org/play?id=59Aj4v5cBex

// from: https://cuelang.org/play/?id=6qSfDcl8A2m

#Data: {x: string, y: string}

All: [...#Data]
All: [{x: "a", y: "b"}, {x: "c", y: "d"}]

#Get: {
  #filter: string
  
  _#search: [for d in All if d.x == #filter {d}]
  _#valid: len(_#search) & 1
  
  _#search[0]
}


#Stringify: {
  #input: #Data
  s: "x=\(#input.x)  y=\(#input.y)"
}

str: #Stringify & {#input: #Get & { #filter: "a" }}

If I turn #Stringify.s into an embedded string, the same error comes back

[verdverm]

This looks like a closedness issue, related to embedding and embedded scalars

There are a number of open issues / questions around embedding, especially as it comes to definitions and closedness

• https://github.com/cue-lang/cue/milestone/17 (multiple)
• Proposal: don't allow the introduction of new (non-hidden) definitions in a closed struct #543 (proposal)

[roman-mazur]

Marking this as answered: the original example does work with the latest CUE release.