Simple go program for generating terraform variables.tf files from cue definitions.

generate_terraform.go

// Apply @generate_terraform_variables(filename="variables.tf") to a definition you want to output as a variables file.
package main

import (
	"fmt"
	"os"
	"strings"
	"text/template"

	"cuelang.org/go/cue"
	"cuelang.org/go/cue/cuecontext"
	"cuelang.org/go/cue/load"
)

const VARIABLES_TEMPLATE = `
variable "{{ .Name }}" {
  type = "{{ .Type }}"
  {{- if .Default }}
  default = {{ .Default }}
  {{- end}}
}
`

type VariableDetails struct {
	Type    string
	Default string
	Name    string
}

func getType(val cue.Value) (string, error) {
	asdf := fmt.Sprintf("%v", val)
	switch asdf {
	case "string":
		return "string", nil
	case "int":
		return "number", nil
	case "float":
		return "number", nil
	case "bool":
		return "boolean", nil
	default:
		return "", fmt.Errorf("Unknown type: %s", asdf)
	}
}

func outputVariables(val cue.Value) error {
	if val.Kind() == cue.StructKind {
		iterator, err := val.Fields(cue.Definitions(true))
		if err != nil {
			return err
		}

		for iterator.Next() {
			definition := iterator.Value()
			att := definition.Attributes(cue.FieldAttr)
			for _, x := range att {
				if x.Name() == "generate_terraform_variables" {
					var builder strings.Builder
					builder.WriteString("// Generated by Cue\n")
					template := template.New("generate_terraform_variables")
					template.Parse(VARIABLES_TEMPLATE)
					fieldIterator, err := definition.Fields(cue.Optional(true))
					if err != nil {
						return err
					}

					for fieldIterator.Next() {
						field := fieldIterator.Value()

						label, _ := field.Label()

						kind, err := getType(field)
						if err != nil {
							return err
						}

						details := VariableDetails{
							Name: label,
							Type: kind,
						}
						template.Execute(&builder, details)
					}
					filename, found, err := x.Lookup(0, "filename")
					if err != nil {
						return err
					}

					if !found {
						return fmt.Errorf("filename not found")
					}

					file, err := os.Create(filename)
					if err != nil {
						return err
					}
					file.WriteString(builder.String())
				}
			}
		}
	}

	return nil
}

func main() {
	c := cuecontext.New()

	instances := load.Instances([]string{}, &load.Config{Module: "lazytest.io/config", Package: "config"})

	for _, bi := range instances {
		if bi.Err != nil {
			fmt.Println("Error during load:", bi.Err)
			continue
		}

		value := c.BuildInstance(bi)
		if value.Err() != nil {
			fmt.Println("Error during build:", value.Err())
			continue
		}

		err := outputVariables(value)
		if err != nil {
			fmt.Printf("Error: %v", err)
			os.Exit(1)
		}
	}
}