Improve context types (#10402)

* Allow declaration merging for DefaultContext

* Use DefaultContext instead of any

* Fix test

* Add changeset

Co-authored-by: Alessia Bellisario <alessia@apollographql.com>
Co-authored-by: Jerel Miller <jerelmiller@gmail.com>

.changeset/spotty-kings-unite.md

@@ -0,0 +1,5 @@
+---
+"@apollo/client": patch
+---
+
+Improve context types

src/__tests__/ApolloClient.ts

@@ -2245,7 +2245,7 @@ describe('ApolloClient', () => {
             query: {kind: Kind.DOCUMENT, definitions: []},
             variables: {foo: 'bar'},
             errorPolicy: 'none',
-            context: null,
+            context: undefined,
             fetchPolicy: 'cache-first',
             pollInterval: 100,
             notifyOnNetworkStatusChange: true,

src/core/types.ts

@@ -13,7 +13,7 @@ import { IsStrictlyAny } from '../utilities';
 
 export { TypedDocumentNode } from '@graphql-typed-document-node/core';
 
-export type DefaultContext = Record<string, any>;
+export interface DefaultContext extends Record<string, any> {};
 
 export type QueryListener = (queryInfo: QueryInfo) => void;
 
@@ -140,7 +140,7 @@ export type ApolloQueryResult<T> = {
   */
   errors?: ReadonlyArray<GraphQLError>;
   /**
-  * The single Error object that is passed to onError and useQuery hooks, and is often thrown during manual `client.query` calls. 
+  * The single Error object that is passed to onError and useQuery hooks, and is often thrown during manual `client.query` calls.
   * This will contain both a NetworkError field and any GraphQLErrors.
   * See https://www.apollographql.com/docs/react/data/error-handling/ for more information.
   */

src/core/watchQueryOptions.ts

@@ -73,7 +73,7 @@ export interface QueryOptions<TVariables = OperationVariables, TData = any> {
   /**
    * Context to be passed to link execution chain
    */
-  context?: any;
+  context?: DefaultContext;
 
   /**
    * Specifies the {@link FetchPolicy} to be used for this query
@@ -159,7 +159,7 @@ export interface NextFetchPolicyContext<TData, TVariables> {
 export interface FetchMoreQueryOptions<TVariables, TData = any> {
   query?: DocumentNode | TypedDocumentNode<TData, TVariables>;
   variables?: Partial<TVariables>;
-  context?: any;
+  context?: DefaultContext;
 }
 
 export type UpdateQueryFn<

src/link/context/index.ts

@@ -1,10 +1,11 @@
 import { ApolloLink, Operation, GraphQLRequest, NextLink } from '../core';
 import { Observable, ObservableSubscription } from '../../utilities';
+import { DefaultContext } from '../../core';
 
 export type ContextSetter = (
   operation: GraphQLRequest,
-  prevContext: any,
-) => Promise<any> | any;
+  prevContext: DefaultContext,
+) => Promise<DefaultContext> | DefaultContext;
 
 export function setContext(setter: ContextSetter): ApolloLink {
   return new ApolloLink((operation: Operation, forward: NextLink) => {

src/link/core/types.ts

@@ -1,4 +1,5 @@
 import { DocumentNode, ExecutionResult, GraphQLError } from "graphql";
+import { DefaultContext } from "../../core";
 export { DocumentNode };
 
 import { Observable } from "../../utilities";
@@ -60,7 +61,7 @@ export interface GraphQLRequest {
   query: DocumentNode;
   variables?: Record<string, any>;
   operationName?: string;
-  context?: Record<string, any>;
+  context?: DefaultContext;
   extensions?: Record<string, any>;
 }
 
@@ -69,13 +70,13 @@ export interface Operation {
   variables: Record<string, any>;
   operationName: string;
   extensions: Record<string, any>;
-  setContext: (context: Record<string, any>) => Record<string, any>;
-  getContext: () => Record<string, any>;
+  setContext: (context: DefaultContext) => DefaultContext;
+  getContext: () => DefaultContext;
 }
 
 export interface SingleExecutionResult<
   TData = Record<string, any>,
-  TContext = Record<string, any>,
+  TContext = DefaultContext,
   TExtensions = Record<string, any>
 > extends ExecutionResult<TData, TExtensions> {
   data?: Data<TData>;