add ExecutionPartialResultNP

Author: mohawk2

src/execution/execute.js

@@ -110,15 +110,21 @@ export type ExecutionResult = {
 };
 
 /**
- * A partial result of GraphQL execution.
- *
- *   - `errors` is included when any errors occurred as a non-empty array.
- *   - `data` is the result of a successful execution of the query.
+ * A partial result of GraphQL execution. `data` and `errors` as above.
+ * "NP" = "Not Promise".
  */
-export type ExecutionPartialResult<T> = MaybePromise<{
+export type ExecutionPartialResultNP<T> = {
   errors?: $ReadOnlyArray<GraphQLError>,
   data?: T | null,
-}>;
+};
+
+/**
+ * A partial result of GraphQL execution. `data` and `errors` as above.
+ * This version might be a promise.
+ */
+export type ExecutionPartialResult<T> = MaybePromise<
+  ExecutionPartialResultNP<T>,
+>;
 
 export type ExecutionArgs = {|
   schema: GraphQLSchema,
@@ -235,18 +241,8 @@ function executeImpl(
  */
 function mergeErrors(
   context: ExecutionContext,
-  result: ExecutionPartialResult<mixed>,
-): ExecutionPartialResult<mixed> {
-  invariant(!getPromise(result), 'Cannot call on a Promise.');
-  // this contortion is to persuade Flow that it really really is a Promise
-  if (
-    result instanceof Promise ||
-    (typeof result === 'object' &&
-      result !== null &&
-      typeof result.then === 'function')
-  ) {
-    throw new Error('Cannot call on a Promise.');
-  }
+  result: ExecutionPartialResultNP<mixed>,
+): ExecutionPartialResultNP<mixed> {
   const errors = context.errors;
   context.errors = [];
   return { data: result.data, errors: [...errors, ...(result.errors || [])] };
@@ -593,8 +589,8 @@ function executeFields(
 }
 
 function mergeEPRs(
-  eprMap: ObjMap<ExecutionPartialResult<mixed>>,
-): ExecutionPartialResult<mixed> {
+  eprMap: ObjMap<ExecutionPartialResultNP<mixed>>,
+): ExecutionPartialResultNP<mixed> {
   const keys = Object.keys(eprMap);
   const values = keys.map(name => eprMap[name]);
   return values.reduce(
@@ -738,9 +734,9 @@ function doesFragmentConditionMatch(
  * This is akin to bluebird's `Promise.props`, but implemented only using
  * `Promise.all` so it will work with any implementation of ES6 promises.
  */
-function promiseForObject<T>(
-  object: ObjMap<ExecutionPartialResult<T>>,
-): ExecutionPartialResult<T> {
+function promiseForObject(
+  object: ObjMap<Promise<ExecutionPartialResultNP<mixed>>>,
+): Promise<ExecutionPartialResultNP<mixed>> {
   const keys = Object.keys(object);
   const valuesAndPromises = keys.map(name => object[name]);
   return Promise.all(valuesAndPromises)
@@ -1137,8 +1133,8 @@ function completeListValue(
 }
 
 function flattenEPRs(
-  eprs: $ReadOnlyArray<ExecutionPartialResult<mixed>>,
-): ExecutionPartialResult<mixed> {
+  eprs: $ReadOnlyArray<ExecutionPartialResultNP<mixed>>,
+): ExecutionPartialResultNP<mixed> {
   const errors = [];
   const data = [];
   forEach((eprs: any), item => {