Add "dependent default" example to v.optional

website/src/routes/api/(schemas)/optional/index.mdx

@@ -71,6 +71,25 @@ const OptionalEntrySchema = v.object({
 });
 ```
 
+### Optional schema with a dependent default value
+
+Object schema with an optional `version` entry, where the default value depends on the `id` entry.
+
+```ts
+const OptionalEntrySchema = v.pipe(
+ v.object({
+ id: v.string(),
+ version: v.optional(v.string()),
+ }),
+ v.transform((input) => {
+ if (!input.version) {
+ input.version = getVersionFromId(input.id);
+ }
+ return input;
+ }),
+);
+```
+
 ### Unwrap optional schema
 
 Use <Link href="../unwrap/">`unwrap`</Link> to undo the effect of `optional`.