Implement support for async generator functions and for-await statements

packages/babel-plugin-transform-async-generator-functions/src/index.js

@@ -0,0 +1,36 @@
+import remapAsyncToGenerator from "babel-helper-remap-async-to-generator";
+
+export default function ({ types: t }) {
+  let yieldStarVisitor = {
+    Function(path) {
+      path.skip();
+    },
+
+    YieldExpression({ node }, state) {
+      if (!node.delegate) return;
+      let callee = state.addHelper("asyncGeneratorDelegate");
+      node.argument = t.callExpression(callee, [
+        t.callExpression(state.addHelper("asyncIterator"), [node.argument]),
+        t.memberExpression(state.addHelper("asyncGenerator"), t.identifier("await"))
+      ]);
+    }
+  };
+
+  return {
+    inherits: require("babel-plugin-syntax-async-generators"),
+    visitor: {
+      Function(path, state) {
+        if (!path.node.async || !path.node.generator) return;
+
+        path.get("body").traverse(yieldStarVisitor, state);
+
+        remapAsyncToGenerator(path, state.file, {
+          wrapAsync: t.memberExpression(
+            state.addHelper("asyncGenerator"), t.identifier("wrap")),
+          wrapAwait: t.memberExpression(
+            state.addHelper("asyncGenerator"), t.identifier("await"))
+        });
+      }
+    }
+  };
+}