cuesonnet

Validate Jsonnet data against CUE constraints.

Usage

Example Schema

import "time"

#Schema: {
	// Basic schema
	firstName: string
	lastName:  string
	age:       int
	birthday:  string

	// Refine as needed
	#Title:    =~"^[A-Z]" | error("must start with an uppercase letter")
	firstName: #Title
	lastName:  #Title
	age:       >0
	birthday:  time.Format("01/02/2006")

	// Defaults
	gopher: bool | *true
}

// Apply the schema to root
#Schema

Example Jsonnet

{
  firstName: 'Jim',
  lastName: 'Jimbly',
  age: 45,
  birthday: '01/02/2003',
}

Embedding the schema is the recommended pattern:

//go:embed schema.cue
var schema cuesonnet.Schema

var result MyStruct
if err := schema.Decode(r, &result); err != nil {
    // handle validation errors
}

Schema notes

Human-readable errors: CUE constraint errors surface raw expressions by default (e.g. out of bound =~"..."). Use | error("message") in your schema to replace them with plain language - see #Title in the example above.

float vs number: JSON has one number type. go-jsonnet serializes 50.0 as 50, which CUE treats as int and rejects against float. Use number for fields that should accept whole-number values; reserve float only when integers must be rejected.

Tests

testdata/ contains a large list of schemas and Jsonnet fixtures covering CUE features (types, constraints, structs, lists, disjunctions, defaults, definitions, composition, stdlib) and Jsonnet features (functions, comprehensions, conditionals, inheritance, multiline strings, self-reference, stdlib). See cuesonnet_test.go and cuesonnet_decode_test.go.

License

MIT