Optimize async to generator (#8267)

* Optimize async to generator

We can reuse the step function, avoiding a closure on every invocation.

* Rename step

packages/babel-core/test/fixtures/transformation/misc/regression-2892/output.js

@@ -7,7 +7,9 @@ exports.default = void 0;
 
 function _instanceof(left, right) { if (right != null && typeof Symbol !== "undefined" && right[Symbol.hasInstance]) { return right[Symbol.hasInstance](left); } else { return left instanceof right; } }
 
-function _asyncToGenerator(fn) { return function () { var self = this, args = arguments; return new Promise(function (resolve, reject) { var gen = fn.apply(self, args); function step(key, arg) { try { var info = gen[key](arg); var value = info.value; } catch (error) { reject(error); return; } if (info.done) { resolve(value); } else { Promise.resolve(value).then(_next, _throw); } } function _next(value) { step("next", value); } function _throw(err) { step("throw", err); } _next(); }); }; }
+function asyncGeneratorStep(gen, resolve, reject, _next, _throw, key, arg) { try { var info = gen[key](arg); var value = info.value; } catch (error) { reject(error); return; } if (info.done) { resolve(value); } else { Promise.resolve(value).then(_next, _throw); } }
+
+function _asyncToGenerator(fn) { return function () { var self = this, args = arguments; return new Promise(function (resolve, reject) { var gen = fn.apply(self, args); function _next(value) { asyncGeneratorStep(gen, resolve, reject, _next, _throw, "next", value); } function _throw(err) { asyncGeneratorStep(gen, resolve, reject, _next, _throw, "throw", err); } _next(undefined); }); }; }
 
 function _classCallCheck(instance, Constructor) { if (!_instanceof(instance, Constructor)) { throw new TypeError("Cannot call a class as a function"); } }
 

packages/babel-helpers/src/helpers.js

@@ -238,12 +238,7 @@ helpers.asyncGeneratorDelegate = () => template.program.ast`
 `;
 
 helpers.asyncToGenerator = () => template.program.ast`
-  export default function _asyncToGenerator(fn) {
+  function asyncGeneratorStep(gen, resolve, reject, _next, _throw, key, arg) {
-    return function () {
-      var self = this, args = arguments;
-      return new Promise(function (resolve, reject) {
-        var gen = fn.apply(self, args);
-        function step(key, arg) {
     try {
       var info = gen[key](arg);
       var value = info.value;
@@ -258,10 +253,20 @@ helpers.asyncToGenerator = () => template.program.ast`
       Promise.resolve(value).then(_next, _throw);
     }
   }
-        function _next(value) { step("next", value); }
-        function _throw(err) { step("throw", err); }
 
-        _next();
+  export default function _asyncToGenerator(fn) {
+    return function () {
+      var self = this, args = arguments;
+      return new Promise(function (resolve, reject) {
+        var gen = fn.apply(self, args);
+        function _next(value) {
+          asyncGeneratorStep(gen, resolve, reject, _next, _throw, "next", value);
+        }
+        function _throw(err) {
+          asyncGeneratorStep(gen, resolve, reject, _next, _throw, "throw", err);
+        }
+
+        _next(undefined);
       });
     };
   }

packages/babel-plugin-transform-async-to-generator/test/fixtures/async-to-generator/shadowed-promise-import/output.mjs

@@ -1,4 +1,6 @@
-function _asyncToGenerator(fn) { return function () { var self = this, args = arguments; return new Promise(function (resolve, reject) { var gen = fn.apply(self, args); function step(key, arg) { try { var info = gen[key](arg); var value = info.value; } catch (error) { reject(error); return; } if (info.done) { resolve(value); } else { Promise.resolve(value).then(_next, _throw); } } function _next(value) { step("next", value); } function _throw(err) { step("throw", err); } _next(); }); }; }
+function asyncGeneratorStep(gen, resolve, reject, _next, _throw, key, arg) { try { var info = gen[key](arg); var value = info.value; } catch (error) { reject(error); return; } if (info.done) { resolve(value); } else { Promise.resolve(value).then(_next, _throw); } }
+
+function _asyncToGenerator(fn) { return function () { var self = this, args = arguments; return new Promise(function (resolve, reject) { var gen = fn.apply(self, args); function _next(value) { asyncGeneratorStep(gen, resolve, reject, _next, _throw, "next", value); } function _throw(err) { asyncGeneratorStep(gen, resolve, reject, _next, _throw, "throw", err); } _next(undefined); }); }; }
 
 import _Promise from 'somewhere';
 

packages/babel-plugin-transform-async-to-generator/test/fixtures/async-to-generator/shadowed-promise-nested/output.js

@@ -1,4 +1,6 @@
-function _asyncToGenerator(fn) { return function () { var self = this, args = arguments; return new Promise(function (resolve, reject) { var gen = fn.apply(self, args); function step(key, arg) { try { var info = gen[key](arg); var value = info.value; } catch (error) { reject(error); return; } if (info.done) { resolve(value); } else { Promise.resolve(value).then(_next, _throw); } } function _next(value) { step("next", value); } function _throw(err) { step("throw", err); } _next(); }); }; }
+function asyncGeneratorStep(gen, resolve, reject, _next, _throw, key, arg) { try { var info = gen[key](arg); var value = info.value; } catch (error) { reject(error); return; } if (info.done) { resolve(value); } else { Promise.resolve(value).then(_next, _throw); } }
+
+function _asyncToGenerator(fn) { return function () { var self = this, args = arguments; return new Promise(function (resolve, reject) { var gen = fn.apply(self, args); function _next(value) { asyncGeneratorStep(gen, resolve, reject, _next, _throw, "next", value); } function _throw(err) { asyncGeneratorStep(gen, resolve, reject, _next, _throw, "throw", err); } _next(undefined); }); }; }
 
 let _Promise;
 

packages/babel-plugin-transform-async-to-generator/test/fixtures/async-to-generator/shadowed-promise/output.js

@@ -1,4 +1,6 @@
-function _asyncToGenerator(fn) { return function () { var self = this, args = arguments; return new Promise(function (resolve, reject) { var gen = fn.apply(self, args); function step(key, arg) { try { var info = gen[key](arg); var value = info.value; } catch (error) { reject(error); return; } if (info.done) { resolve(value); } else { Promise.resolve(value).then(_next, _throw); } } function _next(value) { step("next", value); } function _throw(err) { step("throw", err); } _next(); }); }; }
+function asyncGeneratorStep(gen, resolve, reject, _next, _throw, key, arg) { try { var info = gen[key](arg); var value = info.value; } catch (error) { reject(error); return; } if (info.done) { resolve(value); } else { Promise.resolve(value).then(_next, _throw); } }
+
+function _asyncToGenerator(fn) { return function () { var self = this, args = arguments; return new Promise(function (resolve, reject) { var gen = fn.apply(self, args); function _next(value) { asyncGeneratorStep(gen, resolve, reject, _next, _throw, "next", value); } function _throw(err) { asyncGeneratorStep(gen, resolve, reject, _next, _throw, "throw", err); } _next(undefined); }); }; }
 
 let _Promise;
 

packages/babel-plugin-transform-async-to-generator/test/fixtures/regression/4943/output.js

@@ -1,6 +1,8 @@
 "use strict";
 
-function _asyncToGenerator(fn) { return function () { var self = this, args = arguments; return new Promise(function (resolve, reject) { var gen = fn.apply(self, args); function step(key, arg) { try { var info = gen[key](arg); var value = info.value; } catch (error) { reject(error); return; } if (info.done) { resolve(value); } else { Promise.resolve(value).then(_next, _throw); } } function _next(value) { step("next", value); } function _throw(err) { step("throw", err); } _next(); }); }; }
+function asyncGeneratorStep(gen, resolve, reject, _next, _throw, key, arg) { try { var info = gen[key](arg); var value = info.value; } catch (error) { reject(error); return; } if (info.done) { resolve(value); } else { Promise.resolve(value).then(_next, _throw); } }
+
+function _asyncToGenerator(fn) { return function () { var self = this, args = arguments; return new Promise(function (resolve, reject) { var gen = fn.apply(self, args); function _next(value) { asyncGeneratorStep(gen, resolve, reject, _next, _throw, "next", value); } function _throw(err) { asyncGeneratorStep(gen, resolve, reject, _next, _throw, "throw", err); } _next(undefined); }); }; }
 
 function mandatory(paramName) {
   throw new Error(`Missing parameter: ${paramName}`);

packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/async-function/output.mjs

@@ -1,4 +1,6 @@
-function _asyncToGenerator(fn) { return function () { var self = this, args = arguments; return new Promise(function (resolve, reject) { var gen = fn.apply(self, args); function step(key, arg) { try { var info = gen[key](arg); var value = info.value; } catch (error) { reject(error); return; } if (info.done) { resolve(value); } else { Promise.resolve(value).then(_next, _throw); } } function _next(value) { step("next", value); } function _throw(err) { step("throw", err); } _next(); }); }; }
+function asyncGeneratorStep(gen, resolve, reject, _next, _throw, key, arg) { try { var info = gen[key](arg); var value = info.value; } catch (error) { reject(error); return; } if (info.done) { resolve(value); } else { Promise.resolve(value).then(_next, _throw); } }
+
+function _asyncToGenerator(fn) { return function () { var self = this, args = arguments; return new Promise(function (resolve, reject) { var gen = fn.apply(self, args); function _next(value) { asyncGeneratorStep(gen, resolve, reject, _next, _throw, "next", value); } function _throw(err) { asyncGeneratorStep(gen, resolve, reject, _next, _throw, "throw", err); } _next(undefined); }); }; }
 
 export default {
   function(name) {

packages/babel-preset-env/test/fixtures/preset-options-add-used-built-ins/regenerator-used-async/output.mjs

@@ -1,7 +1,9 @@
 import "regenerator-runtime/runtime";
 import "core-js/modules/es6.promise";
 
-function _asyncToGenerator(fn) { return function () { var self = this, args = arguments; return new Promise(function (resolve, reject) { var gen = fn.apply(self, args); function step(key, arg) { try { var info = gen[key](arg); var value = info.value; } catch (error) { reject(error); return; } if (info.done) { resolve(value); } else { Promise.resolve(value).then(_next, _throw); } } function _next(value) { step("next", value); } function _throw(err) { step("throw", err); } _next(); }); }; }
+function asyncGeneratorStep(gen, resolve, reject, _next, _throw, key, arg) { try { var info = gen[key](arg); var value = info.value; } catch (error) { reject(error); return; } if (info.done) { resolve(value); } else { Promise.resolve(value).then(_next, _throw); } }
+
+function _asyncToGenerator(fn) { return function () { var self = this, args = arguments; return new Promise(function (resolve, reject) { var gen = fn.apply(self, args); function _next(value) { asyncGeneratorStep(gen, resolve, reject, _next, _throw, "next", value); } function _throw(err) { asyncGeneratorStep(gen, resolve, reject, _next, _throw, "throw", err); } _next(undefined); }); }; }
 
 function a() {
   return _a.apply(this, arguments);