generates default object for a given zod schema, you can supply an object to override the defaults

zodSchemaDefaults.ts

import { z } from 'zod'

/**
 *  generates default object for a given zod schema, you can supply an object to override the defaults
 */
export const zodSchemaDefaults = <Schema extends z.ZodFirstPartySchemaTypes>(
  schema: Schema,
  override?: Partial<z.TypeOf<Schema>>
): z.TypeOf<Schema> => {
  if (override !== undefined && typeof override !== 'object') {
    return override
  }

  switch (schema._def.typeName) {
    case z.ZodFirstPartyTypeKind.ZodDefault:
      return schema._def.defaultValue()
    case z.ZodFirstPartyTypeKind.ZodObject: {
      // The switch wasn't able to infer this but the cast should
      // be safe.
      return Object.fromEntries(
        Object.entries((schema as z.SomeZodObject).shape).map(
          ([key, value]) => [key, zodSchemaDefaults(value, override?.[key])]
        )
      )
    }
    case z.ZodFirstPartyTypeKind.ZodString:
      return ''
    case z.ZodFirstPartyTypeKind.ZodNull:
      return null
    case z.ZodFirstPartyTypeKind.ZodNullable:
      return null
    case z.ZodFirstPartyTypeKind.ZodNumber:
      return 0
    case z.ZodFirstPartyTypeKind.ZodBoolean:
      return false
    // etc
    default:
      return null
  }
}