From b1c50b01f2ec2453c7cc8aa9ef63b3c7f212033d Mon Sep 17 00:00:00 2001
From: Logan Smyth <loganfsmyth@gmail.com>
Date: Sat, 12 Mar 2016 12:28:22 -0800
Subject: [PATCH] Ensure that we push and pop evenly so things don't fail to
 queue - fixes T7199

---
 .../test/fixtures/regression/T7199/actual.js      |  2 ++
 .../test/fixtures/regression/T7199/expected.js    | 15 +++++++++++++++
 .../test/fixtures/regression/T7199/options.json   |  8 ++++++++
 packages/babel-traverse/src/context.js            |  8 +++++++-
 4 files changed, 32 insertions(+), 1 deletion(-)
 create mode 100644 packages/babel-plugin-transform-es2015-modules-commonjs/test/fixtures/regression/T7199/actual.js
 create mode 100644 packages/babel-plugin-transform-es2015-modules-commonjs/test/fixtures/regression/T7199/expected.js
 create mode 100644 packages/babel-plugin-transform-es2015-modules-commonjs/test/fixtures/regression/T7199/options.json

diff --git a/packages/babel-plugin-transform-es2015-modules-commonjs/test/fixtures/regression/T7199/actual.js b/packages/babel-plugin-transform-es2015-modules-commonjs/test/fixtures/regression/T7199/actual.js
new file mode 100644
index 0000000000..8688ce9a54
--- /dev/null
+++ b/packages/babel-plugin-transform-es2015-modules-commonjs/test/fixtures/regression/T7199/actual.js
@@ -0,0 +1,2 @@
+import foo from 'foo';
+const [x] = bar;
diff --git a/packages/babel-plugin-transform-es2015-modules-commonjs/test/fixtures/regression/T7199/expected.js b/packages/babel-plugin-transform-es2015-modules-commonjs/test/fixtures/regression/T7199/expected.js
new file mode 100644
index 0000000000..04d5367ebd
--- /dev/null
+++ b/packages/babel-plugin-transform-es2015-modules-commonjs/test/fixtures/regression/T7199/expected.js
@@ -0,0 +1,15 @@
+'use strict';
+
+var _slicedToArray = function () { function sliceIterator(arr, i) { var _arr = []; var _n = true; var _d = false; var _e = undefined; try { for (var _i = arr[Symbol.iterator](), _s; !(_n = (_s = _i.next()).done); _n = true) { _arr.push(_s.value); if (i && _arr.length === i) break; } } catch (err) { _d = true; _e = err; } finally { try { if (!_n && _i["return"]) _i["return"](); } finally { if (_d) throw _e; } } return _arr; } return function (arr, i) { if (Array.isArray(arr)) { return arr; } else if (Symbol.iterator in Object(arr)) { return sliceIterator(arr, i); } else { throw new TypeError("Invalid attempt to destructure non-iterable instance"); } }; }();
+
+var _foo = require('foo');
+
+var _foo2 = _interopRequireDefault(_foo);
+
+function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { 'default': obj }; }
+
+var _bar = bar;
+
+var _bar2 = _slicedToArray(_bar, 1);
+
+const x = _bar2[0];
diff --git a/packages/babel-plugin-transform-es2015-modules-commonjs/test/fixtures/regression/T7199/options.json b/packages/babel-plugin-transform-es2015-modules-commonjs/test/fixtures/regression/T7199/options.json
new file mode 100644
index 0000000000..bfd4950ba4
--- /dev/null
+++ b/packages/babel-plugin-transform-es2015-modules-commonjs/test/fixtures/regression/T7199/options.json
@@ -0,0 +1,8 @@
+{
+  "plugins": [
+    "transform-es2015-destructuring",
+    "transform-es2015-modules-commonjs",
+    "transform-es3-member-expression-literals",
+    "transform-es3-property-literals"
+  ]
+}
diff --git a/packages/babel-traverse/src/context.js b/packages/babel-traverse/src/context.js
index edad4ea598..b8ffaf0e20 100644
--- a/packages/babel-traverse/src/context.js
+++ b/packages/babel-traverse/src/context.js
@@ -103,7 +103,13 @@ export default class TraversalContext {
     // visit the queue
     for (let path of queue) {
       path.resync();
-      path.pushContext(this);
+
+      if (path.contexts.length === 0 || path.contexts[path.contexts.length - 1] !== this){
+        // The context might already have been pushed when this path was inserted and queued.
+        // If we always re-pushed here, we could get duplicates and risk leaving contexts
+        // on the stack after the traversal has completed, which could break things.
+        path.pushContext(this);
+      }
 
       // this path no longer belongs to the tree
       if (path.key === null) continue;