From 7b0010514e2afc7cfe63efde97e3602ada0d5e56 Mon Sep 17 00:00:00 2001
From: Boopathi Rajaa <me@boopathi.in>
Date: Mon, 25 Sep 2017 14:30:03 +0200
Subject: [PATCH] Fix folding array literals - bail on spread element

+ Fixes #695
+ Fixes #628
+ Related #610
---
 .../__tests__/constant-folding-test.js        |  8 +++++
 .../src/index.js                              | 32 ++++++++++++-------
 .../src/replacements.js                       | 13 ++++++--
 3 files changed, 39 insertions(+), 14 deletions(-)

diff --git a/packages/babel-plugin-minify-constant-folding/__tests__/constant-folding-test.js b/packages/babel-plugin-minify-constant-folding/__tests__/constant-folding-test.js
index 7e7178ba2..408738f40 100644
--- a/packages/babel-plugin-minify-constant-folding/__tests__/constant-folding-test.js
+++ b/packages/babel-plugin-minify-constant-folding/__tests__/constant-folding-test.js
@@ -246,4 +246,12 @@ describe("constant-folding-plugin", () => {
       }
     `
   );
+
+  thePlugin(
+    "should not fold array literals with spread element",
+    `
+      [...bar].reverse();
+      [...foo].join("a");
+    `
+  );
 });
diff --git a/packages/babel-plugin-minify-constant-folding/src/index.js b/packages/babel-plugin-minify-constant-folding/src/index.js
index 8b15665b1..02fd8c9c1 100644
--- a/packages/babel-plugin-minify-constant-folding/src/index.js
+++ b/packages/babel-plugin-minify-constant-folding/src/index.js
@@ -20,18 +20,17 @@ function getName(member) {
 
 function swap(path, member, handlers, ...args) {
   const key = getName(member.node);
-  if (key === undefined) return;
-  let handler = handlers[key];
-  if (
-    typeof handler !== "function" ||
-    !Object.hasOwnProperty.call(handlers, key)
-  ) {
-    if (typeof handlers[FALLBACK_HANDLER] === "function") {
-      handler = handlers[FALLBACK_HANDLER].bind(member.get("object"), key);
-    } else {
-      return false;
-    }
+  if (key === void 0) return false;
+
+  let handler;
+  if (hop(handlers, key) && typeof handlers[key] === "function") {
+    handler = handlers[key];
+  } else if (typeof handlers[FALLBACK_HANDLER] === "function") {
+    handler = handlers[FALLBACK_HANDLER].bind(member.get("object"), key);
+  } else {
+    return false;
   }
+
   const replacement = handler.apply(member.get("object"), args);
   if (replacement) {
     path.replaceWith(replacement);
@@ -172,6 +171,13 @@ module.exports = babel => {
         if (t.isMemberExpression(member)) {
           const helpers = replacements[member.node.object.type];
           if (!helpers || !helpers.calls) return;
+          // find if the input can be constant folded
+          if (
+            typeof helpers.canReplace === "function" &&
+            !helpers.canReplace.call(member.get("object"))
+          ) {
+            return;
+          }
           swap(path, member, helpers.calls, ...node.arguments);
         }
       },
@@ -184,3 +190,7 @@ module.exports = babel => {
     }
   };
 };
+
+function hop(o, key) {
+  return Object.prototype.hasOwnProperty.call(o, key);
+}
diff --git a/packages/babel-plugin-minify-constant-folding/src/replacements.js b/packages/babel-plugin-minify-constant-folding/src/replacements.js
index ae52887d4..db0207786 100644
--- a/packages/babel-plugin-minify-constant-folding/src/replacements.js
+++ b/packages/babel-plugin-minify-constant-folding/src/replacements.js
@@ -19,17 +19,24 @@ module.exports = ({ types: t }) => {
     };
   }
 
+  function hasSpread(node) {
+    return node.elements.some(el => t.isSpreadElement(el));
+  }
+
   return {
     ArrayExpression: {
+      canReplace() {
+        return !hasSpread(this.node);
+      },
       members: {
         length() {
-          if (this.node.elements.some(el => t.isSpreadElement(el))) {
+          if (hasSpread(this.node)) {
             return;
           }
           return t.numericLiteral(this.node.elements.length);
         },
         [FALLBACK_HANDLER](i) {
-          if (this.node.elements.some(el => t.isSpreadElement(el))) {
+          if (hasSpread(this.node)) {
             return;
           }
           if (typeof i === "number" || i.match(/^\d+$/)) {
@@ -51,7 +58,7 @@ module.exports = ({ types: t }) => {
               return evaled.value;
             })
             .join(sep.value);
-          return bad ? undefined : t.stringLiteral(str);
+          return bad ? void 0 : t.stringLiteral(str);
         },
         push(...args) {
           return t.numericLiteral(this.node.elements.length + args.length);