Enable local state only when client resolvers provided. (#4499)

* Enable local state only when client resolvers provided.

If an application was previously using apollo-link-state, updating to
apollo-client@2.5.0 could cause problems because @client fields are now
stripped by the integrated LocalState API, and thus will not be passed
into the link chain.

This commit should ease the transition by enabling the LocalState
functionality only if client resolvers were passed to the ApolloClient
constructor, or the LocalState#setResolvers method has been called.

If no client resolvers have been specified, @client fields will remain in
the query passed to the link chain, so apollo-link-state can still process
them, though a warning will be logged in development.

If you want to use @client directives to read from or write to the cache
without running resolver functions, you can pass an empty resolvers:{} map
to enable the LocalState functionality (including the stripping of @client
fields from queries).

* Refine private LocalState resolvers field type.

The setResolvers method normalizes Resolvers[] arrays into a combined
(non-array) Resolvers object.

packages/apollo-client/src/__tests__/local-state/export.ts

@@ -19,6 +19,7 @@ describe('@client @export tests', () => {
       const client = new ApolloClient({
         cache,
         link: ApolloLink.empty(),
+        resolvers: {},
       });
       cache.writeData({ data: { field: 1 } });
 
@@ -47,6 +48,7 @@ describe('@client @export tests', () => {
       const client = new ApolloClient({
         cache,
         link: ApolloLink.empty(),
+        resolvers: {},
       });
 
       cache.writeData({
@@ -198,6 +200,7 @@ describe('@client @export tests', () => {
     const client = new ApolloClient({
       cache,
       link,
+      resolvers: {},
     });
 
     cache.writeData({
@@ -259,6 +262,7 @@ describe('@client @export tests', () => {
       const client = new ApolloClient({
         cache,
         link,
+        resolvers: {},
       });
 
       cache.writeData({
@@ -307,6 +311,7 @@ describe('@client @export tests', () => {
     const client = new ApolloClient({
       cache: new InMemoryCache(),
       link,
+      resolvers: {},
     });
 
     return client.query({ query }).then(({ data }: any) => {
@@ -360,6 +365,7 @@ describe('@client @export tests', () => {
       const client = new ApolloClient({
         cache,
         link,
+        resolvers: {},
       });
 
       cache.writeData({
@@ -548,6 +554,7 @@ describe('@client @export tests', () => {
       const client = new ApolloClient({
         cache,
         link,
+        resolvers: {},
       });
 
       cache.writeData({
@@ -599,6 +606,7 @@ describe('@client @export tests', () => {
       const client = new ApolloClient({
         cache,
         link,
+        resolvers: {},
       });
 
       cache.writeData({

packages/apollo-client/src/__tests__/local-state/general.ts

@@ -9,6 +9,7 @@ import {
   IntrospectionFragmentMatcher,
 } from 'apollo-cache-inmemory';
 import { ApolloLink, Observable, Operation } from 'apollo-link';
+import { hasDirectives } from 'apollo-utilities';
 
 describe('General functionality', () => {
   it('should not impact normal non-@client use', () => {
@@ -34,6 +35,38 @@ describe('General functionality', () => {
     });
   });
 
+  // TODO The functionality tested here should be removed (along with the test)
+  // once apollo-link-state is fully deprecated.
+  it('should strip @client fields only if client resolvers specified', async () => {
+    const query = gql`
+      {
+        field @client
+      }
+    `;
+
+    const client = new ApolloClient({
+      cache: new InMemoryCache(),
+      link: new ApolloLink(operation => {
+        expect(hasDirectives(['client'], operation.query)).toBe(true);
+        return Observable.of({ data: { field: 'local' } });
+      }),
+    });
+
+    const { warn } = console;
+    const messages: string[] = [];
+    console.warn = (message: string) => messages.push(message);
+    try {
+      const result = await client.query({ query });
+      expect(result.data).toEqual({ field: 'local' });
+      expect(messages).toEqual([
+        'Found @client directives in query but no client resolvers were specified. ' +
+          'You can now pass apollo-link-state resolvers to the ApolloClient constructor.',
+      ]);
+    } finally {
+      console.warn = warn;
+    }
+  });
+
   it('should not interfere with server introspection queries', () => {
     const query = gql`
       ${introspectionQuery}
@@ -232,6 +265,7 @@ describe('Cache manipulation', () => {
       const client = new ApolloClient({
         cache,
         link: ApolloLink.empty(),
+        resolvers: {},
       });
 
       cache.writeQuery({ query, data: { field: 'yo' } });
@@ -410,6 +444,7 @@ describe('Sample apps', () => {
     const client = new ApolloClient({
       link,
       cache: new InMemoryCache(),
+      resolvers: {},
     });
 
     const update = (
@@ -504,6 +539,7 @@ describe('Sample apps', () => {
     const client = new ApolloClient({
       link: ApolloLink.empty(),
       cache: new InMemoryCache(),
+      resolvers: {},
     });
 
     interface Todo {
@@ -749,6 +785,7 @@ describe('Combining client and server state/operations', () => {
     const client = new ApolloClient({
       cache,
       link,
+      resolvers: {},
     });
 
     cache.writeData({
@@ -786,6 +823,7 @@ describe('Combining client and server state/operations', () => {
     const client = new ApolloClient({
       cache,
       link,
+      resolvers: {},
     });
 
     cache.writeData({

packages/apollo-client/src/core/LocalState.ts

@@ -35,7 +35,6 @@ import ApolloClient from '../ApolloClient';
 import { Resolvers, OperationVariables } from './types';
 import { capitalizeFirstLetter } from '../util/capitalizeFirstLetter';
 
-
 export type Resolver = (
   fieldName: string,
   rootValue: any,
@@ -74,7 +73,7 @@ export type LocalStateOptions<TCacheShape> = {
 export class LocalState<TCacheShape> {
   private cache: ApolloCache<TCacheShape>;
   private client: ApolloClient<TCacheShape>;
-  private resolvers: Resolvers | Resolvers[] = {};
+  private resolvers?: Resolvers;
   private fragmentMatcher: FragmentMatcher;
 
   constructor({
@@ -99,6 +98,7 @@ export class LocalState<TCacheShape> {
   }
 
   public addResolvers(resolvers: Resolvers | Resolvers[]) {
+    this.resolvers = this.resolvers || {};
     if (Array.isArray(resolvers)) {
       resolvers.forEach(resolverGroup => {
         this.resolvers = mergeDeep(this.resolvers, resolverGroup);
@@ -114,7 +114,7 @@ export class LocalState<TCacheShape> {
   }
 
   public getResolvers() {
-    return this.resolvers;
+    return this.resolvers || {};
   }
 
   // Run local client resolvers against the incoming query and remote data.
@@ -162,12 +162,21 @@ export class LocalState<TCacheShape> {
   // Client queries contain everything in the incoming document (if a @client
   // directive is found).
   public clientQuery(document: DocumentNode) {
-    return hasDirectives(['client'], document) ? document : null;
+    if (hasDirectives(['client'], document)) {
+      if (this.resolvers) {
+        return document;
+      }
+      invariant.warn(
+        'Found @client directives in query but no client resolvers were specified. ' +
+          'You can now pass apollo-link-state resolvers to the ApolloClient constructor.',
+      );
+    }
+    return null;
   }
 
   // Server queries are stripped of all @client based selection sets.
   public serverQuery(document: DocumentNode) {
-    return removeClientSetsFromDocument(document);
+    return this.resolvers ? removeClientSetsFromDocument(document) : document;
   }
 
   public prepareContext(context = {}) {
@@ -376,7 +385,7 @@ export class LocalState<TCacheShape> {
     ) {
       const resolverType =
         rootValue.__typename || execContext.defaultOperationType;
-      const resolverMap = (this.resolvers as any)[resolverType];
+      const resolverMap = this.resolvers && this.resolvers[resolverType];
       if (resolverMap) {
         const resolve = resolverMap[aliasUsed ? fieldName : aliasedFieldName];
         if (resolve) {