From d78225f440a99e0c6d43679212e1e5b874443cac Mon Sep 17 00:00:00 2001
From: Niklas Mischkulnig <mischnic@users.noreply.github.com>
Date: Wed, 6 Mar 2019 23:06:20 +0100
Subject: [PATCH] Make treeshaking handle "multiassignments"

---
 .../es6/tree-shaking-multiassignment/a.js     |  2 ++
 .../es6/tree-shaking-multiassignment/b.js     |  9 +++++++++
 .../integration-tests/test/scope-hoisting.js  | 19 +++++++++++++++++++
 .../src/scope-hoisting/shake.js               |  4 +++-
 4 files changed, 33 insertions(+), 1 deletion(-)
 create mode 100644 packages/core/integration-tests/test/integration/scope-hoisting/es6/tree-shaking-multiassignment/a.js
 create mode 100644 packages/core/integration-tests/test/integration/scope-hoisting/es6/tree-shaking-multiassignment/b.js

diff --git a/packages/core/integration-tests/test/integration/scope-hoisting/es6/tree-shaking-multiassignment/a.js b/packages/core/integration-tests/test/integration/scope-hoisting/es6/tree-shaking-multiassignment/a.js
new file mode 100644
index 00000000000..9293a7b2545
--- /dev/null
+++ b/packages/core/integration-tests/test/integration/scope-hoisting/es6/tree-shaking-multiassignment/a.js
@@ -0,0 +1,2 @@
+import x, {y} from "./b";
+export default [x, y];
diff --git a/packages/core/integration-tests/test/integration/scope-hoisting/es6/tree-shaking-multiassignment/b.js b/packages/core/integration-tests/test/integration/scope-hoisting/es6/tree-shaking-multiassignment/b.js
new file mode 100644
index 00000000000..0204ca5f91a
--- /dev/null
+++ b/packages/core/integration-tests/test/integration/scope-hoisting/es6/tree-shaking-multiassignment/b.js
@@ -0,0 +1,9 @@
+exports.default = exports.y = exports.z = undefined;
+var y = 'y';
+exports.y = y;
+var z = 'z';
+exports.z = z;
+
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
diff --git a/packages/core/integration-tests/test/scope-hoisting.js b/packages/core/integration-tests/test/scope-hoisting.js
index da271fece17..df12a4a00ec 100644
--- a/packages/core/integration-tests/test/scope-hoisting.js
+++ b/packages/core/integration-tests/test/scope-hoisting.js
@@ -485,6 +485,25 @@ describe('scope hoisting', function() {
       assert(!/.-./.test(contents));
     });
 
+    it('handle export multi-assignment', async function() {
+      let b = await bundle(
+        path.join(
+          __dirname,
+          '/integration/scope-hoisting/es6/tree-shaking-multiassignment/a.js'
+        ),
+        {minify: true}
+      );
+
+      let output = await run(b);
+      assert.deepEqual(output.default, [undefined, 'y']);
+
+      // let contents = await fs.readFile(
+      //   path.join(__dirname, '/dist/a.js'),
+      //   'utf8'
+      // );
+      // assert(!/["']z["']/.test(contents));
+    });
+
     it('support exporting a ES6 module exported as CommonJS', async function() {
       let b = await bundle(
         path.join(
diff --git a/packages/core/parcel-bundler/src/scope-hoisting/shake.js b/packages/core/parcel-bundler/src/scope-hoisting/shake.js
index 0e736e9a17a..d8f37b09e8a 100644
--- a/packages/core/parcel-bundler/src/scope-hoisting/shake.js
+++ b/packages/core/parcel-bundler/src/scope-hoisting/shake.js
@@ -106,7 +106,9 @@ function remove(path) {
   if (path.isAssignmentExpression()) {
     if (path.parentPath.isSequenceExpression()) {
       if (path.parent.expressions.length == 1) {
-        path.parentPath.remove();
+        // replace sequence expression with it's sole child
+        path.parentPath.replaceWith(path);
+        remove(path.parentPath);
       } else {
         path.remove();
       }