feat: allow embedding the operation result type

Author: n1ru4l

packages/core/src/index.ts

@@ -1,15 +1,18 @@
 import type { DocumentNode } from "graphql";
 
+export type OperationResultType = "stream" | "single";
+
 export interface TypedDocumentNode<
   Result = { [key: string]: any },
-  Variables = { [key: string]: any }
+  Variables = { [key: string]: any },
+  ResultType extends OperationResultType = any
 > extends DocumentNode {
   /**
    * This type is used to ensure that the variables you pass in to the query are assignable to Variables
    * and that the Result is assignable to whatever you pass your result to. The method is never actually
    * implemented, but the type is valid because we list it as optional
    */
-  __apiType?: (variables: Variables) => Result;
+  __apiType?: (variables: Variables, resultType: ResultType) => Result;
 }
 
 /**
@@ -18,10 +21,7 @@ export interface TypedDocumentNode<
  * const myQuery = { ... }; // TypedDocumentNode<R, V>
  * type ResultType = ResultOf<typeof myQuery>; // Now it's R
  */
-export type ResultOf<T> = T extends TypedDocumentNode<
-  infer ResultType,
-  infer VariablesType
->
+export type ResultOf<T> = T extends TypedDocumentNode<infer ResultType, any>
   ? ResultType
   : never;
 
@@ -32,8 +32,22 @@ export type ResultOf<T> = T extends TypedDocumentNode<
  * type VariablesType = VariablesOf<typeof myQuery>; // Now it's V
  */
 export type VariablesOf<T> = T extends TypedDocumentNode<
-  infer ResultType,
+  any,
   infer VariablesType
 >
   ? VariablesType
   : never;
+
+/**
+ * Helper for extracting a TypeScript type for operation type from a TypedDocumentNode.
+ * @example
+ * const myQuery = { ... }; // TypedDocumentNode<R, V, O>
+ * type OperationType = VariablesOf<typeof myQuery>; // Now it's O
+ */
+export type OperationTypeOf<T> = T extends TypedDocumentNode<
+  any,
+  any,
+  infer OperationType
+>
+  ? OperationType
+  : never;