Function executeField

packages/executor/src/execution/execute.ts:694–804

* Implements the "Executing fields" section of the spec * In particular, this function figures out the value that the field returns by * calling its resolve function, then calls completeValue to complete promises, * serialize scalars, or execute the sub-selection-set for objects.

(
  exeContext: ExecutionContext,
  parentType: GraphQLObjectType,
  source: unknown,
  fieldNodes: Array<FieldNode>,
  path: Path,
  asyncPayloadRecord?: AsyncPayloadRecord,
)

 * serialize scalars, or execute the sub-selection-set for objects.
 */
function executeField(
  exeContext: ExecutionContext,
  parentType: GraphQLObjectType,
  source: unknown,
  fieldNodes: Array<FieldNode>,
  path: Path,
  asyncPayloadRecord?: AsyncPayloadRecord,
): MaybePromise<unknown> {
  const errors = asyncPayloadRecord?.errors ?? exeContext.errors;
  const fieldDef = getFieldDef(exeContext.schema, parentType, fieldNodes[0]);
  if (!fieldDef) {
    return;
  }

  const returnType = fieldDef.type;
  const resolveFn = fieldDef.resolve ?? exeContext.fieldResolver;

  const info = buildResolveInfo(exeContext, fieldDef, fieldNodes, parentType, path);

  // Get the resolve function, regardless of if its result is normal or abrupt (error).
  try {
    exeContext.signal?.throwIfAborted();
    // Build a JS object of arguments from the field.arguments AST, using the
    // variables scope to fulfill any variable references.
    // TODO: find a way to memoize, in case this field is within a List type.
    const args = getArgumentValues(fieldDef, fieldNodes[0], exeContext.variableValues);

    // The resolve function's optional third argument is a context value that
    // is provided to every resolve function within an execution. It is commonly
    // used to represent an authenticated user, or request-specific caches.
    const contextValue = exeContext.contextValue;

    const result = resolveFn(source, args, contextValue, info);

    let completed;
    if (isPromise(result)) {
      completed = result.then(resolved =>
        completeValue(exeContext, returnType, fieldNodes, info, path, resolved, asyncPayloadRecord),
      );
    } else {
      completed = completeValue(
        exeContext,
        returnType,
        fieldNodes,
        info,
        path,
        result,
        asyncPayloadRecord,
      );
    }

    if (isPromise(completed)) {
      // Note: we don't rely on a `catch` method, but we do expect "thenable"
      // to take a second callback for the error case.
      return completed.then(undefined, rawError => {
        if (rawError instanceof AggregateError) {
          let result: unknown;
          for (let rawErrorItem of rawError.errors) {