Fixes support for defer in mutations

.changeset/tough-ghosts-itch.md

@@ -0,0 +1,7 @@
+---
+"@apollo/client": patch
+---
+
+Fix: unblocks support for defer in mutations
+
+If the `@defer` directive is present in the document passed to `mutate`, the Promise will resolve with the final merged data after the last multipart chunk has arrived in the response.

config/bundlesize.ts

@@ -3,7 +3,7 @@ import { join } from "path";
 import { gzipSync } from "zlib";
 import bytes from "bytes";
 
-const gzipBundleByteLengthLimit = bytes("31.87KB");
+const gzipBundleByteLengthLimit = bytes("32KB");
 const minFile = join("dist", "apollo-client.min.cjs");
 const minPath = join(__dirname, "..", minFile);
 const gzipByteLen = gzipSync(readFileSync(minPath)).byteLength;

src/__tests__/__snapshots__/exports.ts.snap

@@ -369,6 +369,7 @@ Array [
   "getFragmentDefinitions",
   "getFragmentFromSelection",
   "getFragmentQueryDocument",
+  "getGraphQLErrorsFromResult",
   "getInclusionDirectives",
   "getMainDefinition",
   "getOperationDefinition",

src/core/QueryInfo.ts

@@ -3,6 +3,7 @@ import { equal } from "@wry/equality";
 
 import { Cache, ApolloCache } from '../cache';
 import { DeepMerger } from "../utilities"
+import { mergeIncrementalData } from '../utilities/common/incrementalResult';
 import { WatchQueryOptions, ErrorPolicy } from './watchQueryOptions';
 import { ObservableQuery, reobserveCacheFirst } from './ObservableQuery';
 import { QueryListener } from './types';
@@ -373,21 +374,7 @@ export class QueryInfo {
     this.reset();
 
     if ('incremental' in result && isNonEmptyArray(result.incremental)) {
-      let mergedData = this.getDiff().result;
-
-      result.incremental.forEach(({ data, path, errors }) => {
-        for (let i = path.length - 1; i >= 0; --i) {
-          const key = path[i];
-          const isNumericKey = !isNaN(+key);
-          const parent: Record<string | number, any> = isNumericKey ? [] : {};
-          parent[key] = data;
-          data = parent as typeof data;
-        }
-        if (errors) {
-          graphQLErrors.push(...errors);
-        }
-        mergedData = merger.merge(mergedData, data);
-      });
+      const mergedData = mergeIncrementalData(this.getDiff().result, result);
       result.data = mergedData;
 
     // Detect the first chunk of a deferred query and merge it with existing

src/core/QueryManager.ts

@@ -6,7 +6,10 @@ type OperationTypeNode = any;
 import { equal } from '@wry/equality';
 
 import { ApolloLink, execute, FetchResult } from '../link/core';
-import { isExecutionPatchIncrementalResult } from '../utilities/common/incrementalResult';
+import {
+  isExecutionPatchIncrementalResult,
+  isExecutionPatchResult,
+} from '../utilities/common/incrementalResult';
 import { Cache, ApolloCache, canonicalStringify } from '../cache';
 
 import {
@@ -15,6 +18,7 @@ import {
   getOperationName,
   hasClientExports,
   graphQLResultHasError,
+  getGraphQLErrorsFromResult,
   removeConnectionDirectiveFromDocument,
   canUseWeakMap,
   ObservableSubscription,
@@ -27,6 +31,7 @@ import {
   isDocumentNode,
   isNonNullObject,
 } from '../utilities';
+import { mergeIncrementalData } from '../utilities/common/incrementalResult';
 import { ApolloError, isApolloError } from '../errors';
 import {
   QueryOptions,
@@ -248,7 +253,7 @@ export class QueryManager<TStore> {
         (result: FetchResult<TData>) => {
           if (graphQLResultHasError(result) && errorPolicy === 'none') {
             throw new ApolloError({
-              graphQLErrors: result.errors,
+              graphQLErrors: getGraphQLErrorsFromResult(result),
             });
           }
 
@@ -301,7 +306,9 @@ export class QueryManager<TStore> {
           // multiple FetchResult payloads from the ApolloLink chain, so we will
           // probably need to collect those results in this next method and call
           // resolve only later, in an observer.complete function.
-          resolve(storeResult);
+          if (!('hasNext' in storeResult) || storeResult.hasNext === false) {
+            resolve(storeResult);
+          }
         },
 
         error(err: Error) {
@@ -355,12 +362,38 @@ export class QueryManager<TStore> {
     const skipCache = mutation.fetchPolicy === "no-cache";
 
     if (!skipCache && shouldWriteResult(result, mutation.errorPolicy)) {
-      cacheWrites.push({
-        result: result.data,
-        dataId: 'ROOT_MUTATION',
-        query: mutation.document,
-        variables: mutation.variables,
-      });
+      if (!isExecutionPatchIncrementalResult(result)) {
+        cacheWrites.push({
+          result: result.data,
+          dataId: 'ROOT_MUTATION',
+          query: mutation.document,
+          variables: mutation.variables,
+        });
+      }
+      if (isExecutionPatchIncrementalResult(result) && isNonEmptyArray(result.incremental)) {
+        const diff = cache.diff<TData>({
+          id: "ROOT_MUTATION",
+          // The cache complains if passed a mutation where it expects a
+          // query, so we transform mutations and subscriptions to queries
+          // (only once, thanks to this.transformCache).
+          query: this.transform(mutation.document).asQuery,
+          variables: mutation.variables,
+          optimistic: false,
+          returnPartialData: true,
+        });
+        const mergedData = mergeIncrementalData(diff.result, result);
+        if (typeof mergedData !== 'undefined') {
+          // cast the ExecutionPatchResult to FetchResult here since
+          // ExecutionPatchResult never has `data` when returned from the server
+          (result as FetchResult).data = mergedData;
+          cacheWrites.push({
+            result: mergedData,
+            dataId: 'ROOT_MUTATION',
+            query: mutation.document,
+            variables: mutation.variables,
+          })
+        }
+      }
 
       const { updateQueries } = mutation;
       if (updateQueries) {
@@ -421,6 +454,12 @@ export class QueryManager<TStore> {
           // apply those writes to the store by running this reducer again with
           // a write action.
           const { update } = mutation;
+          // Determine whether result is a SingleExecutionResult,
+          // or the final ExecutionPatchResult.
+          const isFinalResult =
+            !isExecutionPatchResult(result) ||
+            (isExecutionPatchIncrementalResult(result) && !result.hasNext);
+
           if (update) {
             if (!skipCache) {
               // Re-read the ROOT_MUTATION data we just wrote into the cache
@@ -438,20 +477,38 @@ export class QueryManager<TStore> {
                 returnPartialData: true,
               });
 
-              if (diff.complete && !(isExecutionPatchIncrementalResult(result))) {
-                result = { ...result, data: diff.result };
+              if (diff.complete) {
+                result = { ...result as FetchResult, data: diff.result };
+                if ('incremental' in result) {
+                  delete result.incremental;
+                }
+                if ('hasNext' in result) {
+                  delete result.hasNext;
+                }
               }
             }
 
-            update(cache, result, {
-              context: mutation.context,
-              variables: mutation.variables,
-            });
+            // If we've received the whole response,
+            // either a SingleExecutionResult or the final ExecutionPatchResult,
+            // call the update function.
+            if (isFinalResult) {
+              update(cache, result, {
+                context: mutation.context,
+                variables: mutation.variables,
+              });
+            }
           }
 
           // TODO Do this with cache.evict({ id: 'ROOT_MUTATION' }) but make it
           // shallow to allow rolling back optimistic evictions.
-          if (!skipCache && !mutation.keepRootFields) {
+          if (
+            !skipCache &&
+            !mutation.keepRootFields &&
+            (
+              !isExecutionPatchResult(result) ||
+              (isExecutionPatchIncrementalResult(result) && !result.hasNext)
+            )
+          ) {
             cache.modify({
               id: 'ROOT_MUTATION',
               fields(value, { fieldName, DELETE }) {
@@ -1053,19 +1110,8 @@ export class QueryManager<TStore> {
       ),
 
       result => {
-        const graphQLErrors = isNonEmptyArray(result.errors)
-          ? result.errors.slice(0)
-          : [];
-
-        if ('incremental' in result && isNonEmptyArray(result.incremental)) {
-          result.incremental.forEach(incrementalResult => {
-            if (incrementalResult.errors) {
-              graphQLErrors.push(...incrementalResult.errors);
-            }
-          });
-        }
-
-        const hasErrors = isNonEmptyArray(graphQLErrors);
+        const graphQLErrors = getGraphQLErrorsFromResult(result);
+        const hasErrors = graphQLErrors.length > 0;
 
         // If we interrupted this request by calling getResultsFromLink again
         // with the same QueryInfo object, we ignore the old results.