introduce completeValue helpers within stream execution

Motivation:
 = code reuse
 = helpers are optimized to decrease the number of ticks.

This results in changes to order in promise resolution with changes to
the value of hasNext.

Author: yaacovCR

src/execution/__tests__/stream-test.ts

@@ -483,11 +483,6 @@ describe('Execute: stream directive', () => {
               },
             ],
           },
-        ],
-        hasNext: true,
-      },
-      {
-        incremental: [
           {
             items: [{ name: 'Leia', id: '3' }],
             path: ['friendList', 2],

src/execution/execute.ts

@@ -904,6 +904,83 @@ function completeValue(
   );
 }
 
+async function completePromiseCatchingErrors(
+  exeContext: ExecutionContext,
+  returnType: GraphQLOutputType,
+  fieldNodes: ReadonlyArray<FieldNode>,
+  info: GraphQLResolveInfo,
+  path: Path,
+  result: Promise<unknown>,
+  asyncPayloadRecord?: AsyncPayloadRecord,
+): Promise<unknown> {
+  try {
+    const resolved = await result;
+    let completed = completeValue(
+      exeContext,
+      returnType,
+      fieldNodes,
+      info,
+      path,
+      resolved,
+      asyncPayloadRecord,
+    );
+    if (isPromise(completed)) {
+      // see: https://github.com/tc39/proposal-faster-promise-adoption
+      // it is faster to await a promise prior to returning it from an async function
+      completed = await completed;
+    }
+    return completed;
+  } catch (rawError) {
+    const errors = asyncPayloadRecord?.errors ?? exeContext.errors;
+    const error = locatedError(rawError, fieldNodes, pathToArray(path));
+    const handledError = handleFieldError(error, returnType, errors);
+    filterSubsequentPayloads(exeContext, path, asyncPayloadRecord);
+    return handledError;
+  }
+}
+
+function completeValueCatchingErrors(
+  exeContext: ExecutionContext,
+  returnType: GraphQLOutputType,
+  fieldNodes: ReadonlyArray<FieldNode>,
+  info: GraphQLResolveInfo,
+  path: Path,
+  result: unknown,
+  asyncPayloadRecord?: AsyncPayloadRecord,
+): PromiseOrValue<unknown> {
+  let completedValue: PromiseOrValue<unknown>;
+  try {
+    completedValue = completeValue(
+      exeContext,
+      returnType,
+      fieldNodes,
+      info,
+      path,
+      result,
+      asyncPayloadRecord,
+    );
+  } catch (rawError) {
+    const errors = asyncPayloadRecord?.errors ?? exeContext.errors;
+    const error = locatedError(rawError, fieldNodes, pathToArray(path));
+    const handledError = handleFieldError(error, returnType, errors);
+    filterSubsequentPayloads(exeContext, path, asyncPayloadRecord);
+    return handledError;
+  }
+
+  if (isPromise(completedValue)) {
+    // Note: we don't rely on a `catch` method, but we do expect "thenable"
+    // to take a second callback for the error case.
+    completedValue = completedValue.then(undefined, (rawError) => {
+      const errors = asyncPayloadRecord?.errors ?? exeContext.errors;
+      const error = locatedError(rawError, fieldNodes, pathToArray(path));
+      const handledError = handleFieldError(error, returnType, errors);
+      filterSubsequentPayloads(exeContext, path, asyncPayloadRecord);
+      return handledError;
+    });
+  }
+  return completedValue;
+}
+
 /**
  * Returns an object containing the `@stream` arguments if a field should be
  * streamed based on the experimental flag, stream directive present and
@@ -1866,69 +1943,17 @@ function executeStreamField(
     parentContext,
     exeContext,
   });
-  let completedItem: PromiseOrValue<unknown>;
-  try {
-    try {
-      if (isPromise(item)) {
-        completedItem = item.then((resolved) =>
-          completeValue(
-            exeContext,
-            itemType,
-            fieldNodes,
-            info,
-            itemPath,
-            resolved,
-            asyncPayloadRecord,
-          ),
-        );
-      } else {
-        completedItem = completeValue(
-          exeContext,
-          itemType,
-          fieldNodes,
-          info,
-          itemPath,
-          item,
-          asyncPayloadRecord,
-        );
-      }
-
-      if (isPromise(completedItem)) {
-        // Note: we don't rely on a `catch` method, but we do expect "thenable"
-        // to take a second callback for the error case.
-        completedItem = completedItem.then(undefined, (rawError) => {
-          const error = locatedError(
-            rawError,
-            fieldNodes,
-            pathToArray(itemPath),
-          );
-          const handledError = handleFieldError(
-            error,
-            itemType,
-            asyncPayloadRecord.errors,
-          );
-          filterSubsequentPayloads(exeContext, itemPath, asyncPayloadRecord);
-          return handledError;
-        });
-      }
-    } catch (rawError) {
-      const error = locatedError(rawError, fieldNodes, pathToArray(itemPath));
-      completedItem = handleFieldError(
-        error,
-        itemType,
-        asyncPayloadRecord.errors,
-      );
-      filterSubsequentPayloads(exeContext, itemPath, asyncPayloadRecord);
-    }
-  } catch (error) {
-    asyncPayloadRecord.errors.push(error);
-    filterSubsequentPayloads(exeContext, path, asyncPayloadRecord);
-    asyncPayloadRecord.addItems(null);
-    return asyncPayloadRecord;
-  }
-
   let completedItems: PromiseOrValue<Array<unknown> | null>;
-  if (isPromise(completedItem)) {
+  if (isPromise(item)) {
+    const completedItem = completePromiseCatchingErrors(
+      exeContext,
+      itemType,
+      fieldNodes,
+      info,
+      itemPath,
+      item,
+      asyncPayloadRecord,
+    );
     completedItems = completedItem.then(
       (value) => [value],
       (error) => {
@@ -1938,6 +1963,23 @@ function executeStreamField(
       },
     );
   } else {
+    let completedItem;
+    try {
+      completedItem = completeValueCatchingErrors(
+        exeContext,
+        itemType,
+        fieldNodes,
+        info,
+        itemPath,
+        item,
+        asyncPayloadRecord,
+      );
+    } catch (error) {
+      asyncPayloadRecord.errors.push(error);
+      filterSubsequentPayloads(exeContext, path, asyncPayloadRecord);
+      asyncPayloadRecord.addItems(null);
+      return asyncPayloadRecord;
+    }
     completedItems = [completedItem];
   }
 
@@ -1968,37 +2010,18 @@ async function executeStreamIteratorItem(
     // don't continue if iterator throws
     return { done: true, value };
   }
-  let completedItem;
-  try {
-    completedItem = completeValue(
+  return {
+    done: false,
+    value: completeValueCatchingErrors(
       exeContext,
       itemType,
       fieldNodes,
       info,
       itemPath,
       item,
       asyncPayloadRecord,
-    );
-
-    if (isPromise(completedItem)) {
-      completedItem = completedItem.then(undefined, (rawError) => {
-        const error = locatedError(rawError, fieldNodes, pathToArray(itemPath));
-        const handledError = handleFieldError(
-          error,
-          itemType,
-          asyncPayloadRecord.errors,
-        );
-        filterSubsequentPayloads(exeContext, itemPath, asyncPayloadRecord);
-        return handledError;
-      });
-    }
-    return { done: false, value: completedItem };
-  } catch (rawError) {
-    const error = locatedError(rawError, fieldNodes, pathToArray(itemPath));
-    const value = handleFieldError(error, itemType, asyncPayloadRecord.errors);
-    filterSubsequentPayloads(exeContext, itemPath, asyncPayloadRecord);
-    return { done: false, value };
-  }
+    ),
+  };
 }
 
 async function executeStreamIterator(