Use async readFile in getRollupDefaultPlugin (#2965)

browser/fs.ts

@@ -4,6 +4,6 @@ const nope = (method: string) => (..._args: any[]): any => {
 
 export const lstatSync = nope('lstatSync');
 export const readdirSync = nope('readdirSync');
-export const readFileSync = nope('readFileSync');
+export const readFile = nope('readFile');
 export const realpathSync = nope('realpathSync');
 export const writeFile = nope('writeFile');

src/utils/defaultPlugin.ts

@@ -1,14 +1,14 @@
 import { Plugin, ResolveIdHook } from '../rollup/types';
 import { error } from './error';
-import { lstatSync, readdirSync, readFileSync, realpathSync } from './fs';
+import { lstatSync, readdirSync, readFile, realpathSync } from './fs';
 import { basename, dirname, isAbsolute, resolve } from './path';
 
 export function getRollupDefaultPlugin(preserveSymlinks: boolean): Plugin {
 	return {
 		name: 'Rollup Core',
 		resolveId: createResolveId(preserveSymlinks) as ResolveIdHook,
 		load(id) {
-			return readFileSync(id, 'utf-8');
+			return readFile(id);
 		},
 		resolveFileUrl({ relativePath, format }) {
 			return relativeUrlMechanisms[format](relativePath);

src/utils/fs.ts

@@ -3,6 +3,11 @@ import { dirname } from './path';
 
 export * from 'fs';
 
+export const readFile = (file: string) =>
+	new Promise<string>((fulfil, reject) =>
+		fs.readFile(file, 'utf-8', (err, contents) => (err ? reject(err) : fulfil(contents)))
+	);
+
 function mkdirpath(path: string) {
 	const dir = dirname(path);
 	try {