fix: use fast union function

lib/paths-cache.js

@@ -7,7 +7,7 @@ import gitIgnoreParser from 'git-ignore-parser';
 import _ from 'underscore-plus'
 import minimatch from 'minimatch'
 import { Directory, File } from 'atom'
-import { execPromise } from './utils'
+import { execPromise, union } from './utils'
 
 export default class PathsCache extends EventEmitter {
   constructor () {
@@ -184,13 +184,13 @@ export default class PathsCache extends EventEmitter {
     }
 
     this._filePathsByProjectDirectory.set(projectDirectory.path,
-      _.union(filePathsArray, filePaths)
+      union(filePathsArray, filePaths)
     )
 
     // Merge file paths into existing array (which contains file paths for a specific directory)
     filePathsArray = this._filePathsByDirectory.get(directory.path) || []
     this._filePathsByDirectory.set(directory.path,
-      _.union(filePathsArray, filePaths)
+      union(filePathsArray, filePaths)
     )
 
     return Promise.all(directories.map(directory =>

lib/utils.js

@@ -12,3 +12,21 @@ export function execPromise(cmd, options) {
     });
   });
 }
+
+// fast merge function
+// https://uilicious.com/blog/javascript-array-push-is-945x-faster-than-array-concat/
+export function merge(arr1: Array<any>, arr2: Array<any>) {
+  if (!arr2.length) return
+  Array.prototype.push.apply(arr1, arr2)
+}
+
+// get unique entries of an array
+export function unique(arr: Array<any>) {
+  return [...new Set(arr)]
+}
+
+// fast union function (replacement for _.union)
+export function union(arr1: Array<any>, arr2: Array<any>) {
+  merge(arr1, arr2)
+  return unique(arr1)
+}