7 replies

Schema_EXTENSION issues with extending a string schema with an empty struct in TypeScript

Is there a reason why the following is not allowed?

const stringObject = Schema.String.pipe(
  Schema.extend(Schema.Struct({}))
)
// Error: extend: unsupported schema or overlapping types, cannot extend string with {}

const stringObject = Schema.String.pipe(
  Schema.extend(Schema.Struct({}))
)
// Error: extend: unsupported schema or overlapping types, cannot extend string with {}

const stringObject = Schema.String.pipe(
  Schema.extend(Schema.Struct({}))
)
// Error: extend: unsupported schema or overlapping types, cannot extend string with {}

const stringObject = Schema.String.pipe(
  Schema.extend(Schema.Struct({}))
)
// Error: extend: unsupported schema or overlapping types, cannot extend string with {}

In TS, it's perfectly fine to have

string & {}

string & {}

string & {}

string & {}. It's commonly used in situations that need to describe a few known values and the "rest". E.g.:

type EventType = "EventA" | "EventB" | string & {}

type EventType = "EventA" | "EventB" | string & {}

type EventType = "EventA" | "EventB" | string & {}

type EventType = "EventA" | "EventB" | string & {}

This will result in having an experience in which one gets correct code suggestions listing

EventA

EventA

EventA

EventA and

EventB

EventB

EventB

EventB as an option but the value can indeed be anything else, too.

Schema_EXTENSION issues with extending a string schema with an empty struct in TypeScript

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