cuegen

CUE AST tips

Adding optional fields to structs

Code:

requiredField := &ast.Field {
  Label: ast.NewIdent("username"),
  Value: ast.NewIdent("string"),
}
optionalField := &ast.Field {
  Label: ast.NewIdent("age"),
  Value: ast.NewIdent("uint"),
}

ast.NewStruct(
  requiredField,

  optionalField.Label,
  token.OPTION,
  optionalField.Value,
)

Given a struct, create a disjunction

In other words, given:

#AllInputs: {
  http_client: {url: string}
  generate: {mapping: string}
  file: {paths: [...string]}
}

Generate a type #Input that conforms to:

#Input: {http_client: {url: string}} | {generate: {mapping: string}} | {file: {paths: [...string]}}

This can be done using the or built-in function in Cue and field comprehension:

#Input: or([for name, config in #AllInputs {(name): config}])

Expressing that using the ast package looks like this:

Code:

collectionIdent := ast.NewIdent("#AllInputs")
disjunctionIdent := ast.NewIdent("#Input")

&ast.Field{
  Label: disjunctionIdent,
  Value: ast.NewCall(ast.NewIdent("or"), ast.NewList(&ast.Comprehension{
    Clauses: []ast.Clause{
      &ast.ForClause{
        Key:    ast.NewIdent("name"),
        Value:  ast.NewIdent("config"),
        Source: collectionIdent,
      },
    },
    Value: ast.NewStruct(&ast.Field{
      Label: interpolateIdent(ast.NewIdent("name")),
      Value: ast.NewIdent("config"),
    }),
  })),
},