From a080c82777895114535bec5a3f92f953e492b30d Mon Sep 17 00:00:00 2001
From: Niklas Mischkulnig <mischnic@users.noreply.github.com>
Date: Mon, 28 Sep 2020 16:22:13 +0200
Subject: [PATCH] [cjs] Skip duplicate reexported bindings in namespace
 reexports (#11739)

---
 packages/babel-helper-module-transforms/src/index.js   | 10 +++++++++-
 .../test/fixtures/amd/export-from/output.js            |  1 +
 .../test/fixtures/loose/export-from/output.js          |  1 +
 .../test/fixtures/interop-loose/export-from/output.js  |  1 +
 .../test/fixtures/interop/export-all/output.js         |  1 +
 .../test/fixtures/interop/export-from/output.js        |  1 +
 .../test/fixtures/lazy-dep/reexport-all/output.js      |  1 +
 .../test/fixtures/lazy-local/reexport-all/output.js    |  1 +
 .../fixtures/lazy-whitelist/reexport-all/output.js     |  2 ++
 .../test/fixtures/regression/T7165/output.js           |  1 +
 .../test/fixtures/strict/export-all/output.js          |  1 +
 .../test/fixtures/loose/export-from-6/output.js        |  1 +
 .../test/fixtures/umd/export-from-6/output.js          |  1 +
 .../test/fixtures/runtime-corejs2/modules/output.js    |  1 +
 .../fixtures/runtime-corejs3/modules-loose/output.js   |  1 +
 .../test/fixtures/runtime-corejs3/modules/output.js    |  1 +
 .../test/fixtures/runtime/modules/output.js            |  1 +
 17 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/packages/babel-helper-module-transforms/src/index.js b/packages/babel-helper-module-transforms/src/index.js
index 854a76fcb3f2..81983f773c09 100644
--- a/packages/babel-helper-module-transforms/src/index.js
+++ b/packages/babel-helper-module-transforms/src/index.js
@@ -236,14 +236,22 @@ function buildNamespaceReexport(metadata, namespace, loose) {
         Object.keys(NAMESPACE).forEach(function(key) {
           if (key === "default" || key === "__esModule") return;
           VERIFY_NAME_LIST;
+          if (key in EXPORTS && EXPORTS[key] === NAMESPACE[key]) return;
 
           EXPORTS[key] = NAMESPACE[key];
         });
       `
-    : template.statement`
+    : // Also skip already assigned bindings if they are strictly equal
+      // to be somewhat more spec-compliant when a file has multiple
+      // namespace re-exports that would cause a binding to be exported
+      // multiple times. However, multiple bindings of the same name that
+      // export the same primitive value are silently skipped
+      // (the spec requires an "ambigous bindings" early error here).
+      template.statement`
         Object.keys(NAMESPACE).forEach(function(key) {
           if (key === "default" || key === "__esModule") return;
           VERIFY_NAME_LIST;
+          if (key in EXPORTS && EXPORTS[key] === NAMESPACE[key]) return;
 
           Object.defineProperty(EXPORTS, key, {
             enumerable: true,
diff --git a/packages/babel-plugin-transform-modules-amd/test/fixtures/amd/export-from/output.js b/packages/babel-plugin-transform-modules-amd/test/fixtures/amd/export-from/output.js
index 7dd0d1811c63..a1f8e7ec0ab0 100644
--- a/packages/babel-plugin-transform-modules-amd/test/fixtures/amd/export-from/output.js
+++ b/packages/babel-plugin-transform-modules-amd/test/fixtures/amd/export-from/output.js
@@ -6,6 +6,7 @@ define(["exports", "foo"], function (_exports, _foo) {
   });
   Object.keys(_foo).forEach(function (key) {
     if (key === "default" || key === "__esModule") return;
+    if (key in _exports && _exports[key] === _foo[key]) return;
     Object.defineProperty(_exports, key, {
       enumerable: true,
       get: function () {
diff --git a/packages/babel-plugin-transform-modules-amd/test/fixtures/loose/export-from/output.js b/packages/babel-plugin-transform-modules-amd/test/fixtures/loose/export-from/output.js
index 9933165d6e9c..84514950346a 100644
--- a/packages/babel-plugin-transform-modules-amd/test/fixtures/loose/export-from/output.js
+++ b/packages/babel-plugin-transform-modules-amd/test/fixtures/loose/export-from/output.js
@@ -4,6 +4,7 @@ define(["exports", "foo"], function (_exports, _foo) {
   _exports.__esModule = true;
   Object.keys(_foo).forEach(function (key) {
     if (key === "default" || key === "__esModule") return;
+    if (key in _exports && _exports[key] === _foo[key]) return;
     _exports[key] = _foo[key];
   });
 });
diff --git a/packages/babel-plugin-transform-modules-commonjs/test/fixtures/interop-loose/export-from/output.js b/packages/babel-plugin-transform-modules-commonjs/test/fixtures/interop-loose/export-from/output.js
index 8901160e3d1b..44ea971b11f9 100644
--- a/packages/babel-plugin-transform-modules-commonjs/test/fixtures/interop-loose/export-from/output.js
+++ b/packages/babel-plugin-transform-modules-commonjs/test/fixtures/interop-loose/export-from/output.js
@@ -6,5 +6,6 @@ var _foo = require("foo");
 
 Object.keys(_foo).forEach(function (key) {
   if (key === "default" || key === "__esModule") return;
+  if (key in exports && exports[key] === _foo[key]) return;
   exports[key] = _foo[key];
 });
diff --git a/packages/babel-plugin-transform-modules-commonjs/test/fixtures/interop/export-all/output.js b/packages/babel-plugin-transform-modules-commonjs/test/fixtures/interop/export-all/output.js
index 95892f7cc67c..9f51a2747fb2 100644
--- a/packages/babel-plugin-transform-modules-commonjs/test/fixtures/interop/export-all/output.js
+++ b/packages/babel-plugin-transform-modules-commonjs/test/fixtures/interop/export-all/output.js
@@ -11,6 +11,7 @@ var _react = babelHelpers.interopRequireWildcard(require("react"));
 Object.keys(_react).forEach(function (key) {
   if (key === "default" || key === "__esModule") return;
   if (Object.prototype.hasOwnProperty.call(_exportNames, key)) return;
+  if (key in exports && exports[key] === _react[key]) return;
   Object.defineProperty(exports, key, {
     enumerable: true,
     get: function () {
diff --git a/packages/babel-plugin-transform-modules-commonjs/test/fixtures/interop/export-from/output.js b/packages/babel-plugin-transform-modules-commonjs/test/fixtures/interop/export-from/output.js
index 2c7b3bc5c6ac..ccb8b014043f 100644
--- a/packages/babel-plugin-transform-modules-commonjs/test/fixtures/interop/export-from/output.js
+++ b/packages/babel-plugin-transform-modules-commonjs/test/fixtures/interop/export-from/output.js
@@ -8,6 +8,7 @@ var _foo = require("foo");
 
 Object.keys(_foo).forEach(function (key) {
   if (key === "default" || key === "__esModule") return;
+  if (key in exports && exports[key] === _foo[key]) return;
   Object.defineProperty(exports, key, {
     enumerable: true,
     get: function () {
diff --git a/packages/babel-plugin-transform-modules-commonjs/test/fixtures/lazy-dep/reexport-all/output.js b/packages/babel-plugin-transform-modules-commonjs/test/fixtures/lazy-dep/reexport-all/output.js
index 2c7b3bc5c6ac..ccb8b014043f 100644
--- a/packages/babel-plugin-transform-modules-commonjs/test/fixtures/lazy-dep/reexport-all/output.js
+++ b/packages/babel-plugin-transform-modules-commonjs/test/fixtures/lazy-dep/reexport-all/output.js
@@ -8,6 +8,7 @@ var _foo = require("foo");
 
 Object.keys(_foo).forEach(function (key) {
   if (key === "default" || key === "__esModule") return;
+  if (key in exports && exports[key] === _foo[key]) return;
   Object.defineProperty(exports, key, {
     enumerable: true,
     get: function () {
diff --git a/packages/babel-plugin-transform-modules-commonjs/test/fixtures/lazy-local/reexport-all/output.js b/packages/babel-plugin-transform-modules-commonjs/test/fixtures/lazy-local/reexport-all/output.js
index 9f28bb11420c..d6832ddafd42 100644
--- a/packages/babel-plugin-transform-modules-commonjs/test/fixtures/lazy-local/reexport-all/output.js
+++ b/packages/babel-plugin-transform-modules-commonjs/test/fixtures/lazy-local/reexport-all/output.js
@@ -8,6 +8,7 @@ var _foo = require("./foo");
 
 Object.keys(_foo).forEach(function (key) {
   if (key === "default" || key === "__esModule") return;
+  if (key in exports && exports[key] === _foo[key]) return;
   Object.defineProperty(exports, key, {
     enumerable: true,
     get: function () {
diff --git a/packages/babel-plugin-transform-modules-commonjs/test/fixtures/lazy-whitelist/reexport-all/output.js b/packages/babel-plugin-transform-modules-commonjs/test/fixtures/lazy-whitelist/reexport-all/output.js
index bc299957cbe3..6de5e257a9fd 100644
--- a/packages/babel-plugin-transform-modules-commonjs/test/fixtures/lazy-whitelist/reexport-all/output.js
+++ b/packages/babel-plugin-transform-modules-commonjs/test/fixtures/lazy-whitelist/reexport-all/output.js
@@ -8,6 +8,7 @@ var _white = require("white");
 
 Object.keys(_white).forEach(function (key) {
   if (key === "default" || key === "__esModule") return;
+  if (key in exports && exports[key] === _white[key]) return;
   Object.defineProperty(exports, key, {
     enumerable: true,
     get: function () {
@@ -20,6 +21,7 @@ var _black = require("black");
 
 Object.keys(_black).forEach(function (key) {
   if (key === "default" || key === "__esModule") return;
+  if (key in exports && exports[key] === _black[key]) return;
   Object.defineProperty(exports, key, {
     enumerable: true,
     get: function () {
diff --git a/packages/babel-plugin-transform-modules-commonjs/test/fixtures/regression/T7165/output.js b/packages/babel-plugin-transform-modules-commonjs/test/fixtures/regression/T7165/output.js
index cc5fe3b4a091..785bcd377c56 100644
--- a/packages/babel-plugin-transform-modules-commonjs/test/fixtures/regression/T7165/output.js
+++ b/packages/babel-plugin-transform-modules-commonjs/test/fixtures/regression/T7165/output.js
@@ -10,6 +10,7 @@ var _bar = require("bar");
 
 Object.keys(_bar).forEach(function (key) {
   if (key === "default" || key === "__esModule") return;
+  if (key in exports && exports[key] === _bar[key]) return;
   Object.defineProperty(exports, key, {
     enumerable: true,
     get: function () {
diff --git a/packages/babel-plugin-transform-modules-commonjs/test/fixtures/strict/export-all/output.js b/packages/babel-plugin-transform-modules-commonjs/test/fixtures/strict/export-all/output.js
index 443315cbadc4..d7ef4d0c5a7c 100644
--- a/packages/babel-plugin-transform-modules-commonjs/test/fixtures/strict/export-all/output.js
+++ b/packages/babel-plugin-transform-modules-commonjs/test/fixtures/strict/export-all/output.js
@@ -27,6 +27,7 @@ var _mod = require("mod");
 Object.keys(_mod).forEach(function (key) {
   if (key === "default" || key === "__esModule") return;
   if (Object.prototype.hasOwnProperty.call(_exportNames, key)) return;
+  if (key in exports && exports[key] === _mod[key]) return;
   Object.defineProperty(exports, key, {
     enumerable: true,
     get: function () {
diff --git a/packages/babel-plugin-transform-modules-umd/test/fixtures/loose/export-from-6/output.js b/packages/babel-plugin-transform-modules-umd/test/fixtures/loose/export-from-6/output.js
index 8405ded47ad5..e779928fa4ed 100644
--- a/packages/babel-plugin-transform-modules-umd/test/fixtures/loose/export-from-6/output.js
+++ b/packages/babel-plugin-transform-modules-umd/test/fixtures/loose/export-from-6/output.js
@@ -16,6 +16,7 @@
   _exports.__esModule = true;
   Object.keys(_foo).forEach(function (key) {
     if (key === "default" || key === "__esModule") return;
+    if (key in _exports && _exports[key] === _foo[key]) return;
     _exports[key] = _foo[key];
   });
 });
diff --git a/packages/babel-plugin-transform-modules-umd/test/fixtures/umd/export-from-6/output.js b/packages/babel-plugin-transform-modules-umd/test/fixtures/umd/export-from-6/output.js
index 46e4a2b27dd2..12df8e30bce1 100644
--- a/packages/babel-plugin-transform-modules-umd/test/fixtures/umd/export-from-6/output.js
+++ b/packages/babel-plugin-transform-modules-umd/test/fixtures/umd/export-from-6/output.js
@@ -18,6 +18,7 @@
   });
   Object.keys(_foo).forEach(function (key) {
     if (key === "default" || key === "__esModule") return;
+    if (key in _exports && _exports[key] === _foo[key]) return;
     Object.defineProperty(_exports, key, {
       enumerable: true,
       get: function () {
diff --git a/packages/babel-plugin-transform-runtime/test/fixtures/runtime-corejs2/modules/output.js b/packages/babel-plugin-transform-runtime/test/fixtures/runtime-corejs2/modules/output.js
index c3eab7f58ed2..061601e92166 100644
--- a/packages/babel-plugin-transform-runtime/test/fixtures/runtime-corejs2/modules/output.js
+++ b/packages/babel-plugin-transform-runtime/test/fixtures/runtime-corejs2/modules/output.js
@@ -16,6 +16,7 @@ var _mod = require("mod");
 
 _Object$keys(_mod).forEach(function (key) {
   if (key === "default" || key === "__esModule") return;
+  if (key in exports && exports[key] === _mod[key]) return;
 
   _Object$defineProperty(exports, key, {
     enumerable: true,
diff --git a/packages/babel-plugin-transform-runtime/test/fixtures/runtime-corejs3/modules-loose/output.js b/packages/babel-plugin-transform-runtime/test/fixtures/runtime-corejs3/modules-loose/output.js
index 2a1a8fe7aa92..2eb624007929 100644
--- a/packages/babel-plugin-transform-runtime/test/fixtures/runtime-corejs3/modules-loose/output.js
+++ b/packages/babel-plugin-transform-runtime/test/fixtures/runtime-corejs3/modules-loose/output.js
@@ -23,6 +23,7 @@ var _mod = require("mod");
 _forEachInstanceProperty(_context = _Object$keys(_mod)).call(_context, function (key) {
   if (key === "default" || key === "__esModule") return;
   if (Object.prototype.hasOwnProperty.call(_exportNames, key)) return;
+  if (key in exports && exports[key] === _mod[key]) return;
   exports[key] = _mod[key];
 });
 
diff --git a/packages/babel-plugin-transform-runtime/test/fixtures/runtime-corejs3/modules/output.js b/packages/babel-plugin-transform-runtime/test/fixtures/runtime-corejs3/modules/output.js
index 75793607c414..02a06aef15ab 100644
--- a/packages/babel-plugin-transform-runtime/test/fixtures/runtime-corejs3/modules/output.js
+++ b/packages/babel-plugin-transform-runtime/test/fixtures/runtime-corejs3/modules/output.js
@@ -28,6 +28,7 @@ var _mod = require("mod");
 _forEachInstanceProperty(_context = _Object$keys(_mod)).call(_context, function (key) {
   if (key === "default" || key === "__esModule") return;
   if (Object.prototype.hasOwnProperty.call(_exportNames, key)) return;
+  if (key in exports && exports[key] === _mod[key]) return;
 
   _Object$defineProperty(exports, key, {
     enumerable: true,
diff --git a/packages/babel-plugin-transform-runtime/test/fixtures/runtime/modules/output.js b/packages/babel-plugin-transform-runtime/test/fixtures/runtime/modules/output.js
index 260de19e94a1..63f11cee7276 100644
--- a/packages/babel-plugin-transform-runtime/test/fixtures/runtime/modules/output.js
+++ b/packages/babel-plugin-transform-runtime/test/fixtures/runtime/modules/output.js
@@ -12,6 +12,7 @@ var _mod = require("mod");
 
 Object.keys(_mod).forEach(function (key) {
   if (key === "default" || key === "__esModule") return;
+  if (key in exports && exports[key] === _mod[key]) return;
   Object.defineProperty(exports, key, {
     enumerable: true,
     get: function () {