perf: introduce completePromisedListItemValue (#4051)

depends on #4050

Author: yaacovCR

src/execution/execute.ts

@@ -1107,19 +1107,17 @@ async function completeAsyncIteratorValue(
     /* c8 ignore start */
     if (isPromise(item)) {
       completedResults.push(
-        completePromisedValue(
+        completePromisedListItemValue(
+          item,
+          graphqlWrappedResult,
           exeContext,
           itemType,
           fieldGroup,
           info,
           itemPath,
-          item,
           incrementalContext,
           deferMap,
-        ).then((resolved) => {
-          graphqlWrappedResult[1].push(...resolved[1]);
-          return resolved[0];
-        }),
+        ),
       );
       containsPromise = true;
     } else if (
@@ -1232,19 +1230,17 @@ function completeListValue(
 
     if (isPromise(item)) {
       completedResults.push(
-        completePromisedValue(
+        completePromisedListItemValue(
+          item,
+          graphqlWrappedResult,
           exeContext,
           itemType,
           fieldGroup,
           info,
           itemPath,
-          item,
           incrementalContext,
           deferMap,
-        ).then((resolved) => {
-          graphqlWrappedResult[1].push(...resolved[1]);
-          return resolved[0];
-        }),
+        ),
       );
       containsPromise = true;
     } else if (
@@ -1334,6 +1330,41 @@ function completeListItemValue(
   return false;
 }
 
+async function completePromisedListItemValue(
+  item: unknown,
+  parent: GraphQLWrappedResult<Array<unknown>>,
+  exeContext: ExecutionContext,
+  itemType: GraphQLOutputType,
+  fieldGroup: FieldGroup,
+  info: GraphQLResolveInfo,
+  itemPath: Path,
+  incrementalContext: IncrementalContext | undefined,
+  deferMap: ReadonlyMap<DeferUsage, DeferredFragmentRecord> | undefined,
+): Promise<unknown> {
+  try {
+    const resolved = await item;
+    let completed = completeValue(
+      exeContext,
+      itemType,
+      fieldGroup,
+      info,
+      itemPath,
+      resolved,
+      incrementalContext,
+      deferMap,
+    );
+    if (isPromise(completed)) {
+      completed = await completed;
+    }
+    parent[1].push(...completed[1]);
+    return completed[0];
+  } catch (rawError) {
+    const errors = (incrementalContext ?? exeContext).errors;
+    handleFieldError(rawError, itemType, fieldGroup, itemPath, errors);
+    return null;
+  }
+}
+
 /**
  * Complete a Scalar or Enum by serializing to a valid value, returning
  * null if serialization is not possible.