Fix bugs related to watching symlinks (#1408)

src/Bundler.js

@@ -56,6 +56,7 @@ class Bundler extends EventEmitter {
     this.pending = false;
     this.loadedAssets = new Map();
     this.watchedAssets = new Map();
+
     this.farm = null;
     this.watcher = null;
     this.hmr = null;
@@ -391,24 +392,27 @@ class Bundler extends EventEmitter {
     return asset;
   }
 
-  watch(path, asset) {
+  async watch(path, asset) {
     if (!this.watcher) {
       return;
     }
 
+    path = await fs.realpath(path);
+
     if (!this.watchedAssets.has(path)) {
       this.watcher.watch(path);
       this.watchedAssets.set(path, new Set());
     }
-
     this.watchedAssets.get(path).add(asset);
   }
 
-  unwatch(path, asset) {
+  async unwatch(path, asset) {
     if (!this.watchedAssets.has(path)) {
       return;
     }
 
+    path = await fs.realpath(path);
+
     let watched = this.watchedAssets.get(path);
     watched.delete(asset);
 

src/utils/fs.js

@@ -7,7 +7,16 @@ exports.writeFile = promisify(fs.writeFile);
 exports.stat = promisify(fs.stat);
 exports.readdir = promisify(fs.readdir);
 exports.unlink = promisify(fs.unlink);
-exports.realpath = promisify(fs.realpath);
+exports.realpath = async function(path) {
+  const realpath = promisify(fs.realpath);
+  try {
+    path = await realpath(path);
+  } catch (e) {
+    // do nothing
+  }
+  return path;
+};
+exports.lstat = promisify(fs.lstat);
 
 exports.exists = function(filename) {
   return new Promise(resolve => {

test/integration/commonjs-with-symlinks/local.js

@@ -0,0 +1,2 @@
+exports.a = 1;
+exports.b = 2;

test/integration/commonjs-with-symlinks/src/index.js

@@ -0,0 +1,5 @@
+var local = require('./symlinked_local');
+
+module.exports = function () {
+  return local.a + local.b;
+};

test/integration/commonjs-with-symlinks/src/symlinked_local.js

@@ -0,0 +1 @@
+../local.js

test/watcher.js

@@ -253,4 +253,29 @@ describe('watcher', function() {
     assert(file.includes('function Foo'));
     assert(file.includes('function Bar'));
   });
+
+  it('should rebuild if the file behind a symlink changes', async function() {
+    await ncp(
+      __dirname + '/integration/commonjs-with-symlinks/',
+      __dirname + '/input'
+    );
+
+    b = bundler(__dirname + '/input/src/index.js', {
+      watch: true
+    });
+
+    let bundle = await b.bundle();
+    let output = await run(bundle);
+
+    assert.equal(output(), 3);
+
+    await fs.writeFile(
+      __dirname + '/input/local.js',
+      'exports.a = 5; exports.b = 5;'
+    );
+
+    bundle = await nextBundle(b);
+    output = await run(bundle);
+    assert.equal(output(), 10);
+  });
 });