add optional asyncToGenerator transformer - closes #321

test/fixtures/transformation/optional-async-to-generator/basic/actual.js

@@ -0,0 +1,3 @@
+var foo = async function () {
+  var wat = await bar();
+};

test/fixtures/transformation/optional-async-to-generator/basic/expected.js

@@ -0,0 +1,42 @@
+"use strict";
+
+var _asyncToGenerator = function (fn) {
+  return function () {
+    var gen = fn.apply(this, arguments);
+
+    return new Promise(function (resolve, reject) {
+      function step(getNext) {
+        var next;
+        try {
+          next = getNext();
+        } catch (e) {
+          reject(e);
+
+          return;
+        }
+        if (next.done) {
+          resolve(next.value);
+
+          return;
+        }
+        Promise.resolve(next.value).then(function (v) {
+          step(function () {
+            return gen.next(v);
+          });
+        }, function (e) {
+          step(function () {
+            return gen["throw"](e);
+          });
+        });
+      }
+
+      step(function () {
+        return gen.next();
+      });
+    });
+  };
+};
+
+var foo = _asyncToGenerator(function* () {
+  var wat = yield bar();
+});

test/fixtures/transformation/optional-async-to-generator/options.json

@@ -0,0 +1,3 @@
+{
+  "optional": ["asyncToGenerator"]
+}