From 1b78c8b0e55ae870f683b870490141b52c901179 Mon Sep 17 00:00:00 2001
From: Braden Wong <13159333+braden-w@users.noreply.github.com>
Date: Thu, 29 May 2025 11:01:10 -0700
Subject: [PATCH] refactor: improve type safety in `getQueryData` by using
 generics

Refactored the `getQueryData` method in `QueryClient` to use generics for type inference instead of type assertion with `as`.

The previous implementation of `getQueryData` relied on a type assertion (`as`) to cast the result of `queryCache.get()`:

```typescript
    return this.#queryCache.get(options.queryHash)?.state.data as
      | TInferredQueryFnData
      | undefined
```

While this works, using generics is a more type-safe and idiomatic approach in TypeScript. It allows the type system to infer the correct type for `TInferredQueryFnData` when `queryCache.get` is called, reducing the need for manual type casting and potential runtime errors if the cast is incorrect.

## Changes

The `getQueryData` method has been updated to pass `TInferredQueryFnData` as a generic type argument to `this.#queryCache.get()`:

**Before:**

```typescript
    return this.#queryCache.get(options.queryHash)?.state.data as
      | TInferredQueryFnData
      | undefined
```

**After:**

```typescript
    return this.#queryCache.get<TInferredQueryFnData>(options.queryHash)?.state
      .data
```

This change leverages the existing generic type parameter `TInferredQueryFnData` already defined in the `getQueryData` signature and `QueryCache#get` method.
---
 packages/query-core/src/queryClient.ts | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/packages/query-core/src/queryClient.ts b/packages/query-core/src/queryClient.ts
index 650d3e5ad6..5154ecb535 100644
--- a/packages/query-core/src/queryClient.ts
+++ b/packages/query-core/src/queryClient.ts
@@ -133,9 +133,8 @@ export class QueryClient {
   >(queryKey: TTaggedQueryKey): TInferredQueryFnData | undefined {
     const options = this.defaultQueryOptions({ queryKey })
 
-    return this.#queryCache.get(options.queryHash)?.state.data as
-      | TInferredQueryFnData
-      | undefined
+    return this.#queryCache.get<TInferredQueryFnData>(options.queryHash)?.state
+      .data
   }
 
   ensureQueryData<