packages/query-core/src/hydration.ts (2)

89-91: Serializing queryKey changes the dehydrated payload shape — document and/or adjust typing

By setting queryKey: serializeData(query.queryKey), the dehydrated payload can now contain a non-QueryKey shape (e.g., superjson’s { json, meta }). However, DehydratedQuery.queryKey is typed as QueryKey (an array), which can mislead consumers who inspect dehydrated.queries on the server. At minimum, document that queryKey is serialized; optionally, widen the type to reflect reality.

Proposed doc update (outside the changed hunk):

// In interface DehydratedQuery
/**
 * Note: `queryKey` is serialized using the same transformer as `.state.data`
 * during dehydration and must be deserialized on hydration. Its runtime shape
 * may not be `QueryKey` until deserialized.
 */
interface DehydratedQuery {
 queryHash: string
 // consider: queryKey: unknown
 queryKey: QueryKey
 ...
}

If you want stricter correctness, consider changing the type to unknown and adapting internal usages. This would be a minor typing break for anyone accessing dehydrated.queries[i].queryKey directly, so weigh it against compatibility.

---

201-205: Defensive deserialization of queryKey to avoid hydration crashes

If a consumer mismatches serializers between dehydrate and hydrate, deserializeData(nextQuery.queryKey) can throw. A small guard prevents hard failures during hydration and falls back to the raw value.

Apply this diff:

- const data = rawData === undefined ? rawData : deserializeData(rawData)
- const queryKey = deserializeData(nextQuery.queryKey)
+ const data = rawData === undefined ? rawData : deserializeData(rawData)
+ let queryKey: QueryKey
+ try {
+ queryKey = deserializeData(nextQuery.queryKey) as QueryKey
+ } catch {
+ // Fallback for older payloads or mismatched serializers
+ queryKey = nextQuery.queryKey as unknown as QueryKey
+ }

packages/query-core/src/__tests__/hydration.test.tsx (1)

1-4: Minor: prefer using vitest’s expect over node:assert for consistency

The helper using Node’s assert is fine, but the suite predominantly uses expect. Consider inlining it with expect(entry).toBeTruthy() to keep a single assertion style.

-import assert from 'node:assert'
...
- const getFirstEntry = (client: QueryClient) => {
- const [entry] = client.getQueryCache().getAll()
- assert(entry, 'cache should not be empty')
- return entry
- }
+ const getFirstEntry = (client: QueryClient) => {
+ const [entry] = client.getQueryCache().getAll()
+ expect(entry).toBeTruthy()
+ return entry!
+ }

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packages/query-core/src/__tests__/hydration.test.tsx (1)

1385-1429: Make the new key-serialization test less brittle

The toMatchObject assertion on Query instances can be fragile due to instance internals. You already assert queryKey and queryHash equality; that’s sufficient.

Apply:

 expect(clientEntry.queryKey).toEqual(queryKey)
 expect(clientEntry.queryKey).toEqual(serverEntry.queryKey)
 expect(clientEntry.queryHash).toEqual(serverEntry.queryHash)
- expect(clientEntry).toMatchObject(serverEntry)

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