From 6230855b71b396d1f308f131ec73e790bdad6d90 Mon Sep 17 00:00:00 2001
From: Abhilash Singh <daft300punk@gmail.com>
Date: Sat, 30 Sep 2017 18:44:51 +0530
Subject: [PATCH] unshiftContainer seems to incorrectly handle function params
 #6150 (#6354)

---
 packages/babel-traverse/src/path/modification.js |  4 +++-
 packages/babel-traverse/test/modification.js     | 13 +++++++++++++
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/packages/babel-traverse/src/path/modification.js b/packages/babel-traverse/src/path/modification.js
index 43dcee54cf..4a7ecfb0ab 100644
--- a/packages/babel-traverse/src/path/modification.js
+++ b/packages/babel-traverse/src/path/modification.js
@@ -20,7 +20,9 @@ export function insertBefore(nodes) {
   ) {
     return this.parentPath.insertBefore(nodes);
   } else if (
-    (this.isNodeType("Expression") && this.listKey !== "params") ||
+    (this.isNodeType("Expression") &&
+      this.listKey !== "params" &&
+      this.listKey !== "arguments") ||
     (this.parentPath.isForStatement() && this.key === "init")
   ) {
     if (this.node) nodes.push(this.node);
diff --git a/packages/babel-traverse/test/modification.js b/packages/babel-traverse/test/modification.js
index 5542badb27..0e0936becc 100644
--- a/packages/babel-traverse/test/modification.js
+++ b/packages/babel-traverse/test/modification.js
@@ -53,6 +53,19 @@ describe("modification", function() {
 
       assert.equal(generateCode(rootPath), "function test(a) {\n  b;\n}");
     });
+
+    it("properly handles more than one arguments", function() {
+      const code = "foo(a, b);";
+      const ast = parse(code);
+      traverse(ast, {
+        CallExpression: function(path) {
+          path.unshiftContainer("arguments", t.identifier("d"));
+          assert.equal(generateCode(path), "foo(d, a, b);");
+          path.unshiftContainer("arguments", t.stringLiteral("s"));
+          assert.equal(generateCode(path), `foo("s", d, a, b);`);
+        },
+      });
+    });
   });
 
   describe("insertBefore", function() {