Value.Cast with Type.Intersect produces incorrect result when partial nested objects are provided

[DemonHa]

When using Value.Cast with a schema defined using Type.Intersect, nested object properties are not correctly coerced if the input contains a partial object. The casting will use the default values even when some values are provided.

Minimal reproduction

const schema = Type.Intersect([
  Type.Object({}),
  Type.Object({
    name: Type.String(),
    age: Type.Optional(Type.Number()),
    location: Type.Object({
      lat: Type.Number(),
      long: Type.Number(),
    }),
    greeting: Type.String(),
  }),
])

const result = coerceValue(schema, { location: {}, greeting: 'Hello' })

// ❌ Actual output:
{
  greeting: '',
  location: { lat: 0, long: 0 },
  name: ''
}

// ✅ Expected output:
{
  greeting: 'Hello',
  location: { lat: 0, long: 0 },
  name: ''
}

console.log(result)

✅ Notes:

• If the location field is removed, the result is correct:

const result2 = coerceValue(schema, { greeting: 'Hello' })
// Output: { greeting: 'Hello', location: { lat: 0, long: 0 }, name: '' }

• Replacing Type.Intersect with Type.Composite resolves the casting issue:

const schema = Type.Composite([...])
const result = coerceValue(schema, { location: {}, greeting: 'Hello' })
// Output: { greeting: 'Hello', location: { lat: 0, long: 0 }, name: '' }

⚠️ Problem with Type.Composite:

The return type is no longer correct when using features like Type.TemplateLiteral with Type.Record. For example:

const schema = Type.Composite([
  Type.Record(Type.TemplateLiteral('x-${string}'), Type.Unknown()),
  Type.Object({
    name: Type.String(),
    ...
  })
])
type t = Static<typeof schema> // Incorrect type inference

✅ Type inference works correctly when using Type.Intersect.

[sinclairzx81]

@DemonHa Hi, thanks for reporting

When using Value.Cast with a schema defined using Type.Intersect, nested object properties are not correctly coerced if the input contains a partial object. The casting will use the default values even when some values are provided.

I have just pushed a fix for this on 0.34.35. If you install the latest you should get these updates. PR is here

---

The return type is no longer correct when using features like Type.TemplateLiteral with Type.Record. For example

Unfortunately, Record type's are not directly compatible with Composite because Composite operations require a finite set of keys to work. The TemplateLiteral provided for the Record key 'x-${string}' yields a infinite set of keys (any possible ${string} value following the x-), so effectively the Composite operation just gives up and makes a "best guess" attempt to composite the remaining types (selecting the Object type only in the example given)

You can somewhat see this distinction by constraining the TemplateLiteral to a finite key set, this causes the Record to transform to an Object, and the Object can then compose via Composite.

TypeScript Link Here

const T = Type.Composite([
  Type.Record(Type.TemplateLiteral('x-${1|2|3|4}'), Type.Unknown()),
  Type.Object({
    name: Type.String(),
  })
])

type T = Static<typeof T> // type T = {
                          //     "x-1": unknown;
                          //     "x-2": unknown;
                          //     "x-3": unknown;
                          //     "x-4": unknown;
                          //     name: string;
                          // }

Providing better Composite / Record support is being considered, but the above behavior is currently by design.

---

Have a look at 0.34.35 and let me know if you have any issues with Cast. Will close up this issue for now though,

Thanks again for reporting
Cheers
S

[DemonHa]

@sinclairzx81 thank you for your response. It seams to be working fine. However when I have this schema:

const schema = Type.Intersect([
  Type.Record(Type.TemplateLiteral('x-${string}'), Type.Unknown()),
  Type.Object({
    name: Type.String(),
    age: Type.Optional(Type.Number()),
    location: Type.Object({
      lat: Type.Number(),
      long: Type.Number(),
    }),
    greeting: Type.String(),
  }),
])

and I run Value.Convert(schema, {}), I get an extra entry "x-(.*)": Object {}"