Adds a preferred-cache-folder option

Author: Maël Nison

src/cli/index.js

@@ -60,6 +60,7 @@ export function main({
     '--modules-folder <path>',
     'rather than installing modules into the node_modules folder relative to the cwd, output them here',
   );
+  commander.option('--preferred-cache-folder <path>', 'specify a custom folder to store the yarn cache if possible');
   commander.option('--cache-folder <path>', 'specify a custom folder to store the yarn cache');
   commander.option('--mutex <type>[:specifier]', 'use a mutex to ensure only one yarn instance is executing');
   commander.option('--emoji [bool]', 'enable emoji in output', process.platform === 'darwin');
@@ -324,6 +325,7 @@ export function main({
       binLinks: commander.binLinks,
       modulesFolder: commander.modulesFolder,
       globalFolder: commander.globalFolder,
+      preferredCacheFolder: commander.preferredCacheFolder,
       cacheFolder: commander.cacheFolder,
       preferOffline: commander.preferOffline,
       captureHar: commander.har,

src/config.js

@@ -279,15 +279,29 @@ export default class Config {
 
     let cacheRootFolder = opts.cacheFolder || this.getOption('cache-folder', true);
 
-    for (let t = 0; t < constants.PREFERRED_MODULE_CACHE_DIRECTORIES.length && !cacheRootFolder; ++t) {
-      const tentativeCacheFolder = constants.PREFERRED_MODULE_CACHE_DIRECTORIES[t];
-
-      try {
-        await fs.mkdirp(tentativeCacheFolder);
-        await fs.writeFile(path.join(tentativeCacheFolder, constants.WTEST_FILENAME), `testing write access`);
-        cacheRootFolder = tentativeCacheFolder;
-      } catch (error) {
-        this.reporter.warn(this.reporter.lang('cacheFolderSkipped', tentativeCacheFolder));
+    if (!cacheRootFolder) {
+      let preferredCacheFolders = constants.PREFERRED_MODULE_CACHE_DIRECTORIES;
+      const preferredCacheFolder = opts.preferredCacheFolder || this.getOption('preferred-cache-folder', true);
+
+      if (preferredCacheFolder) {
+        preferredCacheFolders = [preferredCacheFolder].concat(preferredCacheFolders);
+      }
+
+      for (let t = 0; t < preferredCacheFolders.length && !cacheRootFolder; ++t) {
+        const tentativeCacheFolder = preferredCacheFolders[t];
+
+        try {
+          await fs.mkdirp(tentativeCacheFolder);
+          // eslint-disable-next-line
+          await fs.access(tentativeCacheFolder, fs.constants.R_OK | fs.constants.W_OK | fs.constants.X_OK);
+          cacheRootFolder = tentativeCacheFolder;
+        } catch (error) {
+          this.reporter.warn(this.reporter.lang('cacheFolderSkipped', tentativeCacheFolder));
+        }
+
+        if (cacheRootFolder && t > 0) {
+          this.reporter.warn(this.reporter.lang('cacheFolderSelected', cacheRootFolder));
+        }
       }
     }
 

src/constants.js

@@ -1,5 +1,6 @@
 /* @flow */
 
+const os = require('os');
 const path = require('path');
 const userHome = require('./util/user-home-dir').default;
 
@@ -47,14 +48,17 @@ function getDirectory(category: string): string {
 }
 
 function getPreferredCacheDirectories(): Array<string> {
-  const preferredCacheDirectories = [getDirectory('cache')];
+  const preferredCacheDirectories = [];
 
-  if (process.platform !== 'win32') {
-    preferredCacheDirectories.unshift('/tmp/.yarn-cache');
+  if (process.platform === 'darwin') {
+    preferredCacheDirectories.push(path.join(userHome, 'Library', 'Caches', 'Yarn'));
   }
 
-  if (process.platform === 'darwin') {
-    preferredCacheDirectories.unshift(path.join(userHome, 'Library', 'Caches', 'Yarn'));
+  preferredCacheDirectories.push(getDirectory('cache'));
+
+  if (process.platform !== 'win32') {
+    preferredCacheDirectories.push(path.join(os.tmpdir(), '.yarn-cache'));
+    preferredCacheDirectories.push('/tmp/.yarn-cache');
   }
 
   return preferredCacheDirectories;
@@ -74,7 +78,7 @@ export const LOCKFILE_FILENAME = 'yarn.lock';
 export const METADATA_FILENAME = '.yarn-metadata.json';
 export const TARBALL_FILENAME = '.yarn-tarball.tgz';
 export const CLEAN_FILENAME = '.yarnclean';
-export const WTEST_FILENAME = 'yarn-wtest';
+export const ACCESS_FILENAME = '.yarn-access';
 
 export const DEFAULT_INDENT = '  ';
 export const SINGLE_INSTANCE_PORT = 31997;

src/reporters/lang/en.js

@@ -177,6 +177,7 @@ const messages = {
   cacheFolderSkipped: 'Skipping preferred cache folder $0 because it is not writable.',
   cacheFolderMissing:
     "Yarn hasn't been able to find a cache folder. Please use an explicit --cache-folder option to tell it what location to use, or make one of the preferred locations writable.",
+  cacheFolderSelected: 'Selected the next writable cache folder in the list, will be $0.',
 
   execMissingCommand: 'Missing command name.',
 

src/util/fs.js

@@ -13,6 +13,8 @@ const globModule = require('glob');
 const os = require('os');
 const path = require('path');
 
+export const constants = fs.constants;
+
 export const lockQueue = new BlockingQueue('fs lock');
 
 export const readFileBuffer = promisify(fs.readFile);