feat: export execution algorithm implementation as Executor class

docs/APIReference-Errors.md

@@ -3,7 +3,7 @@ title: graphql/error
 layout: ../_core/GraphQLJSLayout
 category: API Reference
 permalink: /graphql-js/error/
-sublinks: formatError,GraphQLError,locatedError,syntaxError
+sublinks: formatError,GraphQLError,locatedError,syntaxError,GraphQLAggregateError
 next: /graphql-js/execution/
 ---
 
@@ -107,3 +107,20 @@ type GraphQLErrorLocation = {
 
 Given a GraphQLError, format it according to the rules described by the
 Response Format, Errors section of the GraphQL Specification.
+
+### GraphQLAggregateError
+
+```js
+class GraphQLAggregateError extends Error {
+ constructor(
+   errors: Array<Error>,
+   message?: string
+ )
+}
+```
+
+A helper class for bundling multiple distinct errors. When a
+GraphQLAggregateError is thrown during execution of a GraphQL operation,
+a GraphQLError will be produced from each individual errors and will be
+reported separately, according to the rules described by the Response
+Format, Errors section of the GraphQL Specification.

src/README.md

@@ -20,4 +20,3 @@ Each sub directory within is a sub-module of graphql-js:
 - [`graphql/error`](error/README.md): Creating and formatting GraphQL errors.
 - [`graphql/utilities`](utilities/README.md): Common useful computations upon
   the GraphQL language and type objects.
-- [`graphql/subscription`](subscription/README.md): Subscribe to data updates.

src/error/GraphQLAggregateError.ts

@@ -0,0 +1,47 @@
+import { GraphQLError } from './GraphQLError';
+
+/**
+ * A GraphQLAggregateError is a container for multiple errors.
+ *
+ * This helper can be used to report multiple distinct errors simultaneously.
+ * Note that error handlers must be aware aggregated errors may be reported so as to
+ * properly handle the contained errors.
+ *
+ * See also:
+ * https://tc39.es/ecma262/multipage/fundamental-objects.html#sec-aggregate-error-objects
+ * https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/AggregateError
+ * https://github.com/zloirock/core-js/blob/master/packages/core-js/modules/es.aggregate-error.js
+ * https://github.com/sindresorhus/aggregate-error
+ *
+ */
+export class GraphQLAggregateError<T = Error> extends Error {
+  readonly errors!: ReadonlyArray<T>;
+
+  constructor(errors: ReadonlyArray<T>, message?: string) {
+    super(message);
+
+    Object.defineProperties(this, {
+      name: { value: 'GraphQLAggregateError' },
+      message: {
+        value: message,
+        writable: true,
+      },
+      errors: {
+        value: errors,
+      },
+    });
+  }
+
+  get [Symbol.toStringTag](): string {
+    return 'GraphQLAggregateError';
+  }
+}
+
+export function isAggregateOfGraphQLErrors(
+  error: unknown,
+): error is GraphQLAggregateError<GraphQLError> {
+  return (
+    error instanceof GraphQLAggregateError &&
+    error.errors.every((subError) => subError instanceof GraphQLError)
+  );
+}

src/error/__tests__/GraphQLAggregateError-test.ts

@@ -0,0 +1,25 @@
+import { expect } from 'chai';
+import { describe, it } from 'mocha';
+
+import { GraphQLAggregateError } from '../GraphQLAggregateError';
+
+describe('GraphQLAggregateError', () => {
+  it('is a class and is a subclass of Error', () => {
+    const errors = [new Error('Error1'), new Error('Error2')];
+    expect(new GraphQLAggregateError(errors)).to.be.instanceof(Error);
+    expect(new GraphQLAggregateError(errors)).to.be.instanceof(
+      GraphQLAggregateError,
+    );
+  });
+
+  it('has a name, errors, and a message (if provided)', () => {
+    const errors = [new Error('Error1'), new Error('Error2')];
+    const e = new GraphQLAggregateError(errors, 'msg');
+
+    expect(e).to.include({
+      name: 'GraphQLAggregateError',
+      errors,
+      message: 'msg',
+    });
+  });
+});

src/error/index.ts

@@ -1,3 +1,8 @@
+export {
+  GraphQLAggregateError,
+  isAggregateOfGraphQLErrors,
+} from './GraphQLAggregateError';
+
 export { GraphQLError, printError, formatError } from './GraphQLError';
 export type { GraphQLFormattedError } from './GraphQLError';
 

src/execution/README.md

@@ -7,3 +7,8 @@ fulfilling a GraphQL request.
 import { execute } from 'graphql/execution'; // ES6
 var GraphQLExecution = require('graphql/execution'); // CommonJS
 ```
+
+```js
+import { subscribe, createSourceEventStream } from 'graphql/execution'; // ES6
+var GraphQLSubscription = require('graphql/execution'); // CommonJS
+```