Scope hoisting destructuring (#2742)

packages/core/integration-tests/test/integration/scope-hoisting/commonjs/wrap-destructuring-array/a.js

@@ -0,0 +1,3 @@
+(function(){
+  output = require('./b');
+})();

packages/core/integration-tests/test/integration/scope-hoisting/commonjs/wrap-destructuring-array/b.js

@@ -0,0 +1,4 @@
+const x = [1, 2]
+const [a, b] = x;
+
+module.exports = [a, b];

packages/core/integration-tests/test/integration/scope-hoisting/commonjs/wrap-destructuring-array/package.json

@@ -0,0 +1,4 @@
+{
+    "private": true,
+    "browserslist": ["node 8"]
+}

packages/core/integration-tests/test/integration/scope-hoisting/commonjs/wrap-destructuring-object/a.js

@@ -0,0 +1,3 @@
+(function(){
+  output = require('./b');
+})();

packages/core/integration-tests/test/integration/scope-hoisting/commonjs/wrap-destructuring-object/b.js

@@ -0,0 +1,7 @@
+const x = {
+  a: 4,
+  b: 2
+}
+const {a, b} = x;
+
+module.exports = [a, b];

packages/core/integration-tests/test/integration/scope-hoisting/commonjs/wrap-destructuring-object/package.json

@@ -0,0 +1,4 @@
+{
+    "private": true,
+    "browserslist": ["node 8"]
+}

packages/core/integration-tests/test/scope-hoisting.js

@@ -1229,5 +1229,29 @@ describe('scope hoisting', function() {
       let output = await run(b);
       assert.deepEqual(output, 2);
     });
+
+    it('should support wrapping array destructuring declarations', async function() {
+      let b = await bundle(
+        path.join(
+          __dirname,
+          '/integration/scope-hoisting/commonjs/wrap-destructuring-array/a.js'
+        )
+      );
+
+      let output = await run(b);
+      assert.deepEqual(output, [1, 2]);
+    });
+
+    it('should support wrapping object destructuring declarations', async function() {
+      let b = await bundle(
+        path.join(
+          __dirname,
+          '/integration/scope-hoisting/commonjs/wrap-destructuring-object/a.js'
+        )
+      );
+
+      let output = await run(b);
+      assert.deepEqual(output, [4, 2]);
+    });
   });
 });

packages/core/parcel-bundler/src/packagers/JSConcatPackager.js

@@ -283,17 +283,30 @@ class JSConcatPackager extends Packager {
       // so that they can be referenced by other modules directly.
       if (t.isVariableDeclaration(node)) {
         for (let decl of node.declarations) {
-          decls.push(t.variableDeclarator(decl.id));
-          if (decl.init) {
-            body.push(
-              t.expressionStatement(
-                t.assignmentExpression(
-                  '=',
-                  t.identifier(decl.id.name),
-                  decl.init
+          if (t.isObjectPattern(decl.id) || t.isArrayPattern(decl.id)) {
+            for (let prop of Object.values(t.getBindingIdentifiers(decl.id))) {
+              decls.push(t.variableDeclarator(prop));
+            }
+            if (decl.init) {
+              body.push(
+                t.expressionStatement(
+                  t.assignmentExpression('=', decl.id, decl.init)
                 )
-              )
-            );
+              );
+            }
+          } else {
+            decls.push(t.variableDeclarator(decl.id));
+            if (decl.init) {
+              body.push(
+                t.expressionStatement(
+                  t.assignmentExpression(
+                    '=',
+                    t.identifier(decl.id.name),
+                    decl.init
+                  )
+                )
+              );
+            }
           }
         }
       } else if (t.isFunctionDeclaration(node)) {