perf: cache file stats/reads

src/index.js

@@ -8,6 +8,37 @@ const ES6_BROWSER_EMPTY = resolve( __dirname, '../src/empty.js' );
 const CONSOLE_WARN = ( ...args ) => console.warn( ...args ); // eslint-disable-line no-console
 const exts = [ '.js', '.json', '.node' ];
 
+let readFileCache = {};
+const readFileAsync = file => new Promise((fulfil, reject) => fs.readFile(file, (err, contents) => err ? reject(err) : fulfil(contents)));
+const statAsync = file => new Promise((fulfil, reject) => fs.stat(file, (err, contents) => err ? reject(err) : fulfil(contents)));
+function cachedReadFile (file, cb) {
+ if (file in readFileCache === false) {
+ readFileCache[file] = readFileAsync(file).catch(err => {
+ delete readFileCache[file];
+ throw err;
+ });
+ }
+ readFileCache[file].then(contents => cb(null, contents), cb);
+}
+
+let isFileCache = {};
+function cachedIsFile (file, cb) {
+ if (file in isFileCache === false) {
+ isFileCache[file] = statAsync(file)
+ .then(
+ stat => stat.isFile(),
+ err => {
+ if (err.code == 'ENOENT') return false;
+ throw err;
+ }
+ ).catch(err => {
+ delete isFileCache[file];
+ throw err;
+ });
+ }
+ isFileCache[file].then(contents => cb(null, contents), cb);
+}
+
 export default function nodeResolve ( options = {} ) {
  const useModule = options.module !== false;
  const useMain = options.main !== false;
@@ -31,6 +62,11 @@ export default function nodeResolve ( options = {} ) {
  return {
  name: 'node-resolve',
 
+ write () {
+ isFileCache = {}
+ readFileCache = {}
+ },
+
  resolveId ( importee, importer ) {
  if ( /\0/.test( importee ) ) return null; // ignore IDs with null character, these belong to other plugins
 
@@ -99,6 +135,8 @@ export default function nodeResolve ( options = {} ) {
  }
  return pkg;
  },
+ readFile: cachedReadFile,
+ isFile: cachedIsFile,
  extensions: options.extensions
  }, customResolveOptions ),
  ( err, resolved ) => {