perf: 60ms improvement: Replace fs-extra with mkdirp/rimraf/cp-file

In Electron apps, the cost of large modules is very real.

fs-extra is very convenient, but removing it caused 50 fewer unique
files to be required(), resultin in 60ms faster startup!

Before: 557 unique requires (1330-1340ms)
After: 507 unique requires (1270-1280ms)

src/main/handlers.js

@@ -273,7 +273,7 @@ function commandToArgs (command) {
 }
 
 function installLinux () {
-  const fs = require('fs-extra')
+  const fs = require('fs')
   const os = require('os')
   const path = require('path')
 
@@ -326,6 +326,8 @@ function installLinux () {
   function writeIconFile (err, iconFile) {
     if (err) return log.error(err.message)
 
+    const mkdirp = require('mkdirp')
+
     const iconFilePath = path.join(
       os.homedir(),
       '.local',
@@ -333,9 +335,11 @@ function installLinux () {
       'icons',
       'webtorrent-desktop.png'
     )
-    fs.mkdirp(path.dirname(iconFilePath))
-    fs.writeFile(iconFilePath, iconFile, function (err) {
+    mkdirp(path.dirname(iconFilePath), (err) => {
       if (err) return log.error(err.message)
+      fs.writeFile(iconFilePath, iconFile, (err) => {
+        if (err) log.error(err.message)
+      })
     })
   }
 }
@@ -343,7 +347,7 @@ function installLinux () {
 function uninstallLinux () {
   const os = require('os')
   const path = require('path')
-  const fs = require('fs-extra')
+  const rimraf = require('rimraf')
 
   const desktopFilePath = path.join(
     os.homedir(),
@@ -352,7 +356,7 @@ function uninstallLinux () {
     'applications',
     'webtorrent-desktop.desktop'
   )
-  fs.removeSync(desktopFilePath)
+  rimraf(desktopFilePath)
 
   const iconFilePath = path.join(
     os.homedir(),
@@ -361,5 +365,5 @@ function uninstallLinux () {
     'icons',
     'webtorrent-desktop.png'
   )
-  fs.removeSync(iconFilePath)
+  rimraf(iconFilePath)
 }

src/renderer/controllers/subtitles-controller.js

@@ -1,5 +1,5 @@
 const electron = require('electron')
-const fs = require('fs-extra')
+const fs = require('fs')
 const path = require('path')
 const parallel = require('run-parallel')
 

src/renderer/lib/migrations.js

@@ -48,7 +48,7 @@ function run (state) {
 }
 
 function migrate_0_7_0 (saved) {
-  const fs = require('fs-extra')
+  const cpFile = require('cp-file')
   const path = require('path')
 
   saved.torrents.forEach(function (ts) {
@@ -70,7 +70,7 @@ function migrate_0_7_0 (saved) {
       dst = path.join(config.TORRENT_PATH, infoHash + '.torrent')
       // Synchronous FS calls aren't ideal, but probably OK in a migration
       // that only runs once
-      if (src !== dst) fs.copySync(src, dst)
+      if (src !== dst) cpFile.sync(src, dst)
 
       delete ts.torrentPath
       ts.torrentFileName = infoHash + '.torrent'
@@ -85,7 +85,7 @@ function migrate_0_7_0 (saved) {
       dst = path.join(config.POSTER_PATH, infoHash + extension)
       // Synchronous FS calls aren't ideal, but probably OK in a migration
       // that only runs once
-      if (src !== dst) fs.copySync(src, dst)
+      if (src !== dst) cpFile.sync(src, dst)
 
       delete ts.posterURL
       ts.posterFileName = infoHash + extension
@@ -139,7 +139,7 @@ function migrate_0_12_0 (saved) {
     if (!fileOrFolder) return
     try {
       fs.statSync(fileOrFolder)
-    } catch (e) {
+    } catch (err) {
       // Default torrent with "missing path" error. Clear path.
       delete torrentSummary.path
     }

src/renderer/lib/state.js

@@ -109,7 +109,8 @@ function getDefaultPlayState () {
 
 /* If the saved state file doesn't exist yet, here's what we use instead */
 function setupStateSaved (cb) {
-  const fs = require('fs-extra')
+  const cpFile = require('cp-file')
+  const fs = require('fs')
   const parseTorrent = require('parse-torrent')
   const parallel = require('run-parallel')
 
@@ -130,18 +131,16 @@ function setupStateSaved (cb) {
   config.DEFAULT_TORRENTS.map(function (t, i) {
     const infoHash = saved.torrents[i].infoHash
     tasks.push(function (cb) {
-      fs.copy(
+      cpFile(
         path.join(config.STATIC_PATH, t.posterFileName),
-        path.join(config.POSTER_PATH, infoHash + path.extname(t.posterFileName)),
-        cb
-      )
+        path.join(config.POSTER_PATH, infoHash + path.extname(t.posterFileName))
+      ).then(cb).catch(cb)
     })
     tasks.push(function (cb) {
-      fs.copy(
+      cpFile(
         path.join(config.STATIC_PATH, t.torrentFileName),
-        path.join(config.TORRENT_PATH, infoHash + '.torrent'),
-        cb
-      )
+        path.join(config.TORRENT_PATH, infoHash + '.torrent')
+      ).then(cb).catch(cb)
     })
   })
 
@@ -151,6 +150,7 @@ function setupStateSaved (cb) {
   })
 
   function createTorrentObject (t) {
+    // TODO: Doing several fs.readFileSync calls during first startup is not ideal
     const torrent = fs.readFileSync(path.join(config.STATIC_PATH, t.torrentFileName))
     const parsedTorrent = parseTorrent(torrent)
 

src/renderer/webtorrent.js

@@ -6,7 +6,8 @@ const crypto = require('crypto')
 const deepEqual = require('deep-equal')
 const defaultAnnounceList = require('create-torrent').announceList
 const electron = require('electron')
-const fs = require('fs-extra')
+const fs = require('fs')
+const mkdirp = require('mkdirp')
 const musicmetadata = require('musicmetadata')
 const networkAddress = require('network-address')
 const path = require('path')
@@ -203,19 +204,22 @@ function getTorrentFileInfo (file) {
   }
 }
 
-// Every time we resolve a magnet URI, save the torrent file so that we never
-// have to download it again. Never ask the DHT the same question twice.
+// Every time we resolve a magnet URI, save the torrent file so that we can use
+// it on next startup. Starting with the full torrent metadata will be faster
+// than re-fetching it from peers using ut_metadata.
 function saveTorrentFile (torrentKey) {
   const torrent = getTorrent(torrentKey)
-  checkIfTorrentFileExists(torrent.infoHash, function (torrentPath, exists) {
+  const torrentPath = path.join(config.TORRENT_PATH, torrent.infoHash + '.torrent')
+
+  fs.access(torrentPath, fs.constants.R_OK, function (err) {
     const fileName = torrent.infoHash + '.torrent'
-    if (exists) {
+    if (!err) {
       // We've already saved the file
       return ipc.send('wt-file-saved', torrentKey, fileName)
     }
 
     // Otherwise, save the .torrent file, under the app config folder
-    fs.mkdir(config.TORRENT_PATH, function (_) {
+    mkdirp(config.TORRENT_PATH, function (_) {
       fs.writeFile(torrentPath, torrent.torrentFile, function (err) {
         if (err) return console.log('error saving torrent file %s: %o', torrentPath, err)
         console.log('saved torrent file %s', torrentPath)
@@ -225,15 +229,6 @@ function saveTorrentFile (torrentKey) {
   })
 }
 
-// Checks whether we've already resolved a given infohash to a torrent file
-// Calls back with (torrentPath, exists). Logs, does not call back on error
-function checkIfTorrentFileExists (infoHash, cb) {
-  const torrentPath = path.join(config.TORRENT_PATH, infoHash + '.torrent')
-  fs.exists(torrentPath, function (exists) {
-    cb(torrentPath, exists)
-  })
-}
-
 // Save a JPG that represents a torrent.
 // Auto chooses either a frame from a video file, an image, etc
 function generateTorrentPoster (torrentKey) {
@@ -241,7 +236,7 @@ function generateTorrentPoster (torrentKey) {
   torrentPoster(torrent, function (err, buf, extension) {
     if (err) return console.log('error generating poster: %o', err)
     // save it for next time
-    fs.mkdirp(config.POSTER_PATH, function (err) {
+    mkdirp(config.POSTER_PATH, function (err) {
       if (err) return console.log('error creating poster dir: %o', err)
       const posterFileName = torrent.infoHash + extension
       const posterFilePath = path.join(config.POSTER_PATH, posterFileName)