Function getSchemaDefaultGetter

getSchemaDefaultGetter(schema: unknown): undefined | (() => unknown)
Detect if a schema has a default value by validating undefined.

Uses the Standard Schema ~standard.validate API to detect defaults. If the schema accepts undefined and returns a value, that value is the default.

This approach is library-agnostic and works with any Standard Schema compliant library (Zod, Valibot, ArkType, etc.) without needing to introspect internals.
Parameters
- schema: unknown
  The schema to check for a default value.
Returns undefined | (() => unknown)
A factory function returning the default, or undefined if no default exists.
Example
```
const getter = getSchemaDefaultGetter(z.string().default("hello"));
getter?.(); // "hello"

const noDefault = getSchemaDefaultGetter(z.string());
noDefault; // undefined
```
- Defined in remotes/langchain-ai/langgraphjs/main/libs/langgraph-core/src/state/adapter.ts:45