Add helper to extract the result type from a query QueryResult (#1096)

KyleAMathews · claude · web-flow · commit f795a674f216 · 2026-01-07T16:42:48.000+01:00
* feat(db): Export ExtractContext type for extracting query result types

This allows users to extract the result type from a Query instance:

```typescript
import { Query, ExtractContext, GetResult } from '@tanstack/db'

const myQuery = new Query()
  .from({ users })
  .select(({ users }) =&gt; ({ name: users.name }))

type MyQueryResult = GetResult&lt;ExtractContext&lt;typeof myQuery&gt;&gt;
```

Fixes a gap in the public API where ExtractContext was defined but
not re-exported from the main query module.

* chore: Add changeset for ExtractContext export

* feat(db): Add QueryResult helper type for extracting query result types

Adds a simpler API similar to Zod's z.infer:

```typescript
import { Query, QueryResult } from '@tanstack/db'

const myQuery = new Query()
  .from({ users })
  .select(({ users }) =&gt; ({ name: users.name }))

type MyQueryResult = QueryResult&lt;typeof myQuery&gt;
```

This is more ergonomic than the two-step approach:
`GetResult&lt;ExtractContext&lt;typeof myQuery&gt;&gt;`

---------

Co-authored-by: Claude &lt;noreply@anthropic.com&gt;
diff --git a/.changeset/export-extract-context.md b/.changeset/export-extract-context.md
@@ -0,0 +1,18 @@
+---
+'@tanstack/db': patch
+---
+
+Export `QueryResult` helper type for easily extracting query result types (similar to Zod's `z.infer`).
+
+```typescript
+import { Query, QueryResult } from '@tanstack/db'
+
+const myQuery = new Query()
+  .from({ users })
+  .select(({ users }) => ({ name: users.name }))
+
+// Extract the result type - clean and simple!
+type MyQueryResult = QueryResult<typeof myQuery>
+```
+
+Also exports `ExtractContext` for advanced use cases where you need the full context type.
diff --git a/packages/db/src/query/builder/index.ts b/packages/db/src/query/builder/index.ts
@@ -30,6 +30,7 @@ import type {
 import type {
   CompareOptions,
   Context,
+  GetResult,
   GroupByCallback,
   JoinOnCallback,
   MergeContextForJoinCallback,
@@ -887,6 +888,9 @@ export type ExtractContext<T> =
       ? TContext
       : never
 
+// Helper type to extract the result type from a QueryBuilder (similar to Zod's z.infer)
+export type QueryResult<T> = GetResult<ExtractContext<T>>
+
 // Export the types from types.ts for convenience
 export type {
   Context,
diff --git a/packages/db/src/query/index.ts b/packages/db/src/query/index.ts
@@ -10,6 +10,8 @@ export {
   type Source,
   type GetResult,
   type InferResultType,
+  type ExtractContext,
+  type QueryResult,
 } from './builder/index.js'
 
 // Expression functions exports
