Fallback for cache directories

package.json

@@ -33,7 +33,7 @@
     "eslint-plugin-flowtype": "^2.25.0",
     "nyc": "^10.0.0",
     "rimraf": "^2.4.3",
-    "webpack": "^2.1.0-beta.22"
+    "webpack": "^2.2.0-rc"
   },
   "scripts": {
     "clean": "rimraf lib/",

src/fs-cache.js

@@ -83,6 +83,51 @@ const filename = function(source, identifier, options) {
   return hash.read().toString("hex") + ".json.gz";
 };
 
+/**
+ * Handle the cache
+ *
+ * @params {String} directory
+ * @params {Object} params
+ * @params {Function} callback
+ */
+const handleCache = function(directory, params, callback) {
+  const source = params.source;
+  const options = params.options || {};
+  const transform = params.transform;
+  const identifier = params.identifier;
+  const shouldFallback = typeof params.directory !== "string" && directory !== os.tmpdir();
+
+  // Make sure the directory exists.
+  mkdirp(directory, function(err) {
+    // Fallback to tmpdir if node_modules folder not writable
+    if (err) return shouldFallback ? handleCache(os.tmpdir(), params, callback) : callback(err);
+
+    const file = path.join(directory, filename(source, identifier, options));
+
+    return read(file, function(err, content) {
+      let result = {};
+      // No errors mean that the file was previously cached
+      // we just need to return it
+      if (!err) return callback(null, content);
+
+      // Otherwise just transform the file
+      // return it to the user asap and write it in cache
+      try {
+        result = transform(source, options);
+      } catch (error) {
+        return callback(error);
+      }
+
+      return write(file, result, function(err) {
+        // Fallback to tmpdir if node_modules folder not writable
+        if (err) return shouldFallback ? handleCache(os.tmpdir(), params, callback) : callback(err);
+
+        callback(null, result);
+      });
+    });
+  });
+};
+
 /**
  * Retrieve file from cache, or create a new one for future reads
  *
@@ -117,12 +162,6 @@ const filename = function(source, identifier, options) {
  *   });
  */
 module.exports = function(params, callback) {
-  // Spread params into named variables
-  // Forgive user whenever possible
-  const source = params.source;
-  const options = params.options || {};
-  const transform = params.transform;
-  const identifier = params.identifier;
   let directory;
 
   if (typeof params.directory === "string") {
@@ -131,29 +170,5 @@ module.exports = function(params, callback) {
     directory = findCacheDir({ name: "babel-loader" }) || os.tmpdir();
   }
 
-  const file = path.join(directory, filename(source, identifier, options));
-
-  // Make sure the directory exists.
-  return mkdirp(directory, function(err) {
-    if (err) { return callback(err); }
-
-    return read(file, function(err, content) {
-      let result = {};
-      // No errors mean that the file was previously cached
-      // we just need to return it
-      if (!err) { return callback(null, content); }
-
-      // Otherwise just transform the file
-      // return it to the user asap and write it in cache
-      try {
-        result = transform(source, options);
-      } catch (error) {
-        return callback(error);
-      }
-
-      return write(file, result, function(err) {
-        return callback(err, result);
-      });
-    });
-  });
+  handleCache(directory, params, callback);
 };

test/cache.test.js

@@ -206,7 +206,6 @@ test.cb("should have one file per module", (t) => {
   });
 });
 
-
 test.cb("should generate a new file if the identifier changes", (t) => {
   const configs = [
     assign({}, globalConfig, {

test/helpers/createTestDirectory.js

@@ -3,10 +3,14 @@ import mkdirp from "mkdirp";
 import rimraf from "rimraf";
 
 export default function createTestDirectory(baseDirectory, testTitle, cb) {
-  const directory = path.join(baseDirectory, testTitle.replace(/[\/?<>\\:*|"\s]/g, "_"));
+  const directory = path.join(baseDirectory, escapeDirectory(testTitle));
 
   rimraf(directory, (err) => {
     if (err) return cb(err);
     mkdirp(directory, (mkdirErr) => cb(mkdirErr, directory));
   });
 }
+
+function escapeDirectory(directory) {
+  return directory.replace(/[\/?<>\\:*|"\s]/g, "_");
+}