feat: deep merge resolvers

.changeset/cold-dancers-call.md

@@ -0,0 +1,5 @@
+---
+"@apollo/client": minor
+---
+
+`createTestSchema` now uses graphql-tools `mergeResolvers` to merge resolvers instead of a shallow merge.

package.json

@@ -111,6 +111,7 @@
     "@babel/parser": "7.24.1",
     "@changesets/changelog-github": "0.5.0",
     "@changesets/cli": "2.27.1",
+    "@graphql-tools/merge": "^9.0.3",
     "@graphql-tools/schema": "10.0.3",
     "@graphql-tools/utils": "10.0.13",
     "@microsoft/api-extractor": "7.42.3",

src/testing/core/__tests__/createTestSchema.test.tsx

@@ -346,7 +346,7 @@ describe("schema proxy", () => {
     unmount();
   });
 
-  it("does not pollute the original schema", async () => {
+  it("schema.fork does not pollute the original schema", async () => {
     const Profiler = createDefaultProfiler<ViewerQueryData>();
 
     using _fetch = createSchemaFetch(schema);
@@ -876,10 +876,9 @@ describe("schema proxy", () => {
       resolvers: {
         Query: {
           viewer: () => ({
-            name: "Virginia",
             book: {
               colors: ["red", "blue", "green"],
-              title: "The Book",
+              title: "A New Book",
             },
           }),
         },
@@ -997,7 +996,7 @@ describe("schema proxy", () => {
             colors: ["red", "blue", "green"],
             id: "1",
             publishedAt: "2024-01-01",
-            title: "The Book",
+            title: "A New Book",
           },
         },
       });
@@ -1020,12 +1019,217 @@ describe("schema proxy", () => {
             colors: ["red", "blue", "green"],
             id: "1",
             publishedAt: "2024-01-01",
-            title: "The Book",
+            title: "A New Book",
           },
         },
       });
     }
 
     unmount();
   });
+
+  describe("schema.reset", () => {
+    const resetTestSchema = createTestSchema(schemaWithMocks, {
+      Query: {
+        viewer: () => ({
+          book: {
+            text: "Hello World",
+            title: "Orlando: A Biography",
+          },
+        }),
+      },
+      Book: {
+        __resolveType: (obj) => {
+          if ("text" in obj) {
+            return "TextBook";
+          }
+          if ("colors" in obj) {
+            return "ColoringBook";
+          }
+          throw new Error("Could not resolve type");
+        },
+      },
+    });
+    it("setup test where we add resolvers to schema", async () => {
+      const Profiler = createDefaultProfiler<ViewerQueryData>();
+
+      resetTestSchema.add({
+        resolvers: {
+          Query: {
+            viewer: () => ({
+              book: {
+                text: "Hello World",
+                title: "The Waves",
+              },
+            }),
+          },
+        },
+      });
+
+      using _fetch = createSchemaFetch(resetTestSchema);
+
+      const client = new ApolloClient({
+        cache: new InMemoryCache(),
+        uri,
+      });
+
+      const query: TypedDocumentNode<ViewerQueryData> = gql`
+        query {
+          viewer {
+            id
+            name
+            age
+            book {
+              id
+              title
+              publishedAt
+              ... on ColoringBook {
+                colors
+              }
+            }
+          }
+        }
+      `;
+
+      const Fallback = () => {
+        useTrackRenders();
+        return <div>Loading...</div>;
+      };
+
+      const App = () => {
+        return (
+          <React.Suspense fallback={<Fallback />}>
+            <Child />
+          </React.Suspense>
+        );
+      };
+
+      const Child = () => {
+        const result = useSuspenseQuery(query);
+
+        useTrackRenders();
+
+        Profiler.mergeSnapshot({
+          result,
+        } as Partial<{}>);
+
+        return <div>Hello</div>;
+      };
+
+      const { unmount } = renderWithClient(<App />, {
+        client,
+        wrapper: Profiler,
+      });
+
+      // initial suspended render
+      await Profiler.takeRender();
+
+      {
+        const { snapshot } = await Profiler.takeRender();
+
+        expect(snapshot.result?.data).toEqual({
+          viewer: {
+            __typename: "User",
+            age: 42,
+            id: "1",
+            name: "String",
+            book: {
+              __typename: "TextBook",
+              id: "1",
+              publishedAt: "2024-01-01",
+              // value set in this test with .add
+              title: "The Waves",
+            },
+          },
+        });
+      }
+
+      unmount();
+    });
+    it("resets the schema to the original", async () => {
+      const Profiler = createDefaultProfiler<ViewerQueryData>();
+
+      resetTestSchema.reset();
+
+      using _fetch = createSchemaFetch(resetTestSchema);
+
+      const client = new ApolloClient({
+        cache: new InMemoryCache(),
+        uri,
+      });
+
+      const query: TypedDocumentNode<ViewerQueryData> = gql`
+        query {
+          viewer {
+            id
+            name
+            age
+            book {
+              id
+              title
+              publishedAt
+              ... on ColoringBook {
+                colors
+              }
+            }
+          }
+        }
+      `;
+
+      const Fallback = () => {
+        useTrackRenders();
+        return <div>Loading...</div>;
+      };
+
+      const App = () => {
+        return (
+          <React.Suspense fallback={<Fallback />}>
+            <Child />
+          </React.Suspense>
+        );
+      };
+
+      const Child = () => {
+        const result = useSuspenseQuery(query);
+
+        useTrackRenders();
+
+        Profiler.mergeSnapshot({
+          result,
+        } as Partial<{}>);
+
+        return <div>Hello</div>;
+      };
+
+      const { unmount } = renderWithClient(<App />, {
+        client,
+        wrapper: Profiler,
+      });
+
+      // initial suspended render
+      await Profiler.takeRender();
+
+      {
+        const { snapshot } = await Profiler.takeRender();
+
+        expect(snapshot.result?.data).toEqual({
+          viewer: {
+            __typename: "User",
+            age: 42,
+            id: "1",
+            name: "String",
+            book: {
+              __typename: "TextBook",
+              id: "1",
+              publishedAt: "2024-01-01",
+              // original value
+              title: "Orlando: A Biography",
+            },
+          },
+        });
+      }
+
+      unmount();
+    });
+  });
 });

src/testing/core/createTestSchema.ts

@@ -1,6 +1,6 @@
-import { addResolversToSchema } from "@graphql-tools/schema";
 import type { GraphQLSchema } from "graphql";
-
+import { addResolversToSchema } from "@graphql-tools/schema";
+import { mergeResolvers } from "@graphql-tools/merge";
 import type { Resolvers } from "../../core/types.js";
 
 type ProxiedSchema = GraphQLSchema & ProxiedSchemaFns;
@@ -55,7 +55,9 @@ const createTestSchema = (
 
   const fns: ProxiedSchemaFns = {
     add: ({ resolvers: newResolvers }) => {
-      targetResolvers = { ...targetResolvers, ...newResolvers };
+      // @ts-ignore TODO(fixme): IResolvers type does not play well with our Resolvers
+      targetResolvers = mergeResolvers([targetResolvers, newResolvers]);
+
       targetSchema = addResolversToSchema({
         schema: targetSchema,
         resolvers: targetResolvers,