Fix queryType:true, mutationType:true, and subscriptionType:true type policies.

CHANGELOG.md

@@ -1,3 +1,10 @@
+## Apollo Client 3.3.6
+
+### Bug Fixes
+
+- Immediately apply `queryType: true`, `mutationType: true`, and `subscriptionType: true` type policies, rather than waiting for the first time the policy is used, fixing a [regression](https://github.com/apollographql/apollo-client/issues/7443) introduced by [#7065](https://github.com/apollographql/apollo-client/pull/7065). <br/>
+  [@benjamn](https://github.com/benjamn) in [#7463](https://github.com/apollographql/apollo-client/pull/7463)
+
 ## Apollo Client 3.3.5
 
 ### Improvements

src/cache/inmemory/__tests__/policies.ts

@@ -4872,6 +4872,12 @@ describe("type policies", function () {
       }
     });
 
+    expect(cache.readQuery({
+      query: gql`query { __typename }`,
+    })).toEqual({
+      __typename: "RootQuery",
+    });
+
     const ALL_ITEMS = gql`
       query Items {
         __typename
@@ -4921,4 +4927,48 @@ describe("type policies", function () {
       ],
     });
   });
+
+  it("can configure {query,mutation,subscription}Type:true", () => {
+    const cache = new InMemoryCache({
+      typePolicies: {
+        RootQuery: {
+          queryType: true,
+        },
+        RootMutation: {
+          mutationType: true,
+        },
+        RootSubscription: {
+          subscriptionType: true,
+        },
+      }
+    });
+
+    expect(cache.readQuery({
+      query: gql`query { __typename }`,
+    })).toEqual({
+      __typename: "RootQuery",
+    });
+
+    expect(cache.readFragment({
+      id: "ROOT_MUTATION",
+      fragment: gql`
+        fragment MutationTypename on RootMutation {
+          __typename
+        }
+      `,
+    })).toEqual({
+      __typename: "RootMutation",
+    });
+
+    expect(cache.readFragment({
+      id: "ROOT_SUBSCRIPTION",
+      fragment: gql`
+        fragment SubscriptionTypename on RootSubscription {
+          __typename
+        }
+      `,
+    })).toEqual({
+      __typename: "RootSubscription",
+    });
+  });
 });

src/cache/inmemory/policies.ts

@@ -358,7 +358,31 @@ export class Policies {
 
   public addTypePolicies(typePolicies: TypePolicies) {
     Object.keys(typePolicies).forEach(typename => {
-      const incoming = typePolicies[typename];
+      const {
+        queryType,
+        mutationType,
+        subscriptionType,
+        ...incoming
+      } = typePolicies[typename];
+
+      // Though {query,mutation,subscription}Type configurations are rare,
+      // it's important to call setRootTypename as early as possible,
+      // since these configurations should apply consistently for the
+      // entire lifetime of the cache. Also, since only one __typename can
+      // qualify as one of these root types, these three properties cannot
+      // be inherited, unlike the rest of the incoming properties. That
+      // restriction is convenient, because the purpose of this.toBeAdded
+      // is to delay the processing of type/field policies until the first
+      // time they're used, allowing policies to be added in any order as
+      // long as all relevant policies (including policies for supertypes)
+      // have been added by the time a given policy is used for the first
+      // time. In other words, since inheritance doesn't matter for these
+      // properties, there's also no need to delay their processing using
+      // the this.toBeAdded queue.
+      if (queryType) this.setRootTypename("Query", typename);
+      if (mutationType) this.setRootTypename("Mutation", typename);
+      if (subscriptionType) this.setRootTypename("Subscription", typename);
+
       if (hasOwn.call(this.toBeAdded, typename)) {
         this.toBeAdded[typename].push(incoming);
       } else {
@@ -390,10 +414,6 @@ export class Policies {
     // using field policies to merge child objects.
     setMerge(existing, incoming.merge);
 
-    if (incoming.queryType) this.setRootTypename("Query", typename);
-    if (incoming.mutationType) this.setRootTypename("Mutation", typename);
-    if (incoming.subscriptionType) this.setRootTypename("Subscription", typename);
-
     existing.keyFn =
       // Pass false to disable normalization for this typename.
       keyFields === false ? nullKeyFieldsFn :