From d4cc8fefd1c18645c44015b7b6d021aebcc1f37e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Alu=C3=ADsio=20Augusto=20Silva=20Gon=C3=A7alves?=
 <aluisio@aasg.name>
Date: Sat, 17 Jan 2015 23:02:20 -0200
Subject: [PATCH] Add transformer to import regeneratorRuntime from a module

Thanks to facebook/regenerator#167 Regenerator's runtime can be now
required as a module (though not in an easily self-containable way).
This transformer, together with `coreAliasing` and `externalRuntime`,
allows users to ditch a runtime dependency on `6to5`/`6to5-core` to
depend directly on `core-js` and `regenerator`.
---
 lib/6to5/transformation/transform.js             |  1 +
 .../optional-external-regenerator-runtime.js     | 16 ++++++++++++++++
 2 files changed, 17 insertions(+)
 create mode 100644 lib/6to5/transformation/transformers/optional-external-regenerator-runtime.js

diff --git a/lib/6to5/transformation/transform.js b/lib/6to5/transformation/transform.js
index 74079d5d0b..9d32b62fa9 100644
--- a/lib/6to5/transformation/transform.js
+++ b/lib/6to5/transformation/transform.js
@@ -95,6 +95,7 @@ _.each({
 
   typeofSymbol:              require("./transformers/optional-typeof-symbol"),
   coreAliasing:              require("./transformers/optional-core-aliasing"),
+  externalRegenerator:       require("./transformers/optional-external-regenerator-runtime"),
   undefinedToVoid:           require("./transformers/optional-undefined-to-void"),
 
   // spec
diff --git a/lib/6to5/transformation/transformers/optional-external-regenerator-runtime.js b/lib/6to5/transformation/transformers/optional-external-regenerator-runtime.js
new file mode 100644
index 0000000000..9294a6c76e
--- /dev/null
+++ b/lib/6to5/transformation/transformers/optional-external-regenerator-runtime.js
@@ -0,0 +1,16 @@
+var t = require("../../types");
+
+exports.optional = true;
+
+exports.ast = {
+  enter: function (ast, file) {
+    file._regeneratorId = file.addImport("regenerator/runtime-module", "regeneratorRuntime");
+  }
+};
+
+exports.MemberExpression = function (node, parent, scope, context, file) {
+  var obj = node.object;
+  var prop = node.property;
+  if (!t.isReferenced(node, parent) || !t.isReferenced(obj, node)) return;
+  if (obj.name === "regeneratorRuntime") return t.memberExpression(file._regeneratorId, prop);
+};