Use async-to-generator even when regenerator is enabled (#10839)

While it isn't technically needed because regenerator already handles
async functions, it doesn't play well with the Promise detection logic
used by @babel/preset-env's useBuiltIns and @babel/transform-runtime.

The plugin exclusion logic isn't removed, because
1) it will be useful when merging @babel/preset-modules
    into @babel/preset-env
2) if/when regenerator will support injecting a custom promise,
    we can enable this optimization again

packages/babel-plugin-transform-classes/test/fixtures/regression/T6755/output.js

@@ -1,3 +1,7 @@
+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); }); }; }
+
 var Example =
 /*#__PURE__*/
 function () {
@@ -7,21 +11,33 @@ function () {
 
   var _proto = Example.prototype;
 
-  _proto.test1 = function test1() {
-    return regeneratorRuntime.async(function test1$(_context) {
-      while (1) {
-        switch (_context.prev = _context.next) {
-          case 0:
-            _context.next = 2;
-            return regeneratorRuntime.awrap(Promise.resolve(2));
+  _proto.test1 =
+  /*#__PURE__*/
+  function () {
+    var _test = _asyncToGenerator(
+    /*#__PURE__*/
+    regeneratorRuntime.mark(function _callee() {
+      return regeneratorRuntime.wrap(function _callee$(_context) {
+        while (1) {
+          switch (_context.prev = _context.next) {
+            case 0:
+              _context.next = 2;
+              return Promise.resolve(2);
 
-          case 2:
-          case "end":
-            return _context.stop();
+            case 2:
+            case "end":
+              return _context.stop();
+          }
         }
-      }
-    });
-  };
+      }, _callee);
+    }));
+
+    function test1() {
+      return _test.apply(this, arguments);
+    }
+
+    return test1;
+  }();
 
   _proto.test2 =
   /*#__PURE__*/

packages/babel-plugin-transform-regenerator/test/fixtures/regression/4219/output.js

@@ -1,17 +1,26 @@
+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 test(fn) {
-  return function _callee() {
-    var _args = arguments;
-    return regeneratorRuntime.async(function _callee$(_context) {
-      while (1) {
-        switch (_context.prev = _context.next) {
-          case 0:
-            return _context.abrupt("return", fn.apply(void 0, _args));
+  return (
+    /*#__PURE__*/
+    _asyncToGenerator(
+    /*#__PURE__*/
+    regeneratorRuntime.mark(function _callee() {
+      var _args = arguments;
+      return regeneratorRuntime.wrap(function _callee$(_context) {
+        while (1) {
+          switch (_context.prev = _context.next) {
+            case 0:
+              return _context.abrupt("return", fn.apply(void 0, _args));
 
-          case 1:
-          case "end":
-            return _context.stop();
+            case 1:
+            case "end":
+              return _context.stop();
+          }
         }
-      }
-    });
-  };
+      }, _callee);
+    }))
+  );
 }

packages/babel-preset-env/data/overlapping-plugins.js

@@ -4,7 +4,8 @@ module.exports = new Map();
 
 // async -> regenerator is better than async -> generator -> regenerator
 ifIncluded("transform-regenerator")
-  .isUnnecessary("transform-async-to-generator");
+  // https://github.com/babel/babel/issues/10678
+  // .isUnnecessary("transform-async-to-generator");
 
 function ifIncluded(name) {
   const set = new Set();

packages/babel-preset-env/test/fixtures/corejs2/usage-regenerator-used-async/output.mjs

@@ -1,13 +1,28 @@
 import "regenerator-runtime/runtime";
+import "core-js/modules/es6.promise";
+import "core-js/modules/es6.object.to-string";
+
+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 regeneratorRuntime.async(function a$(_context) {
-    while (1) {
-      switch (_context.prev = _context.next) {
-        case 0:
-        case "end":
-          return _context.stop();
+  return _a.apply(this, arguments);
+}
+
+function _a() {
+  _a = _asyncToGenerator(
+  /*#__PURE__*/
+  regeneratorRuntime.mark(function _callee() {
+    return regeneratorRuntime.wrap(function _callee$(_context) {
+      while (1) {
+        switch (_context.prev = _context.next) {
+          case 0:
+          case "end":
+            return _context.stop();
+        }
       }
-    }
-  });
+    }, _callee);
+  }));
+  return _a.apply(this, arguments);
 }

packages/babel-preset-env/test/fixtures/corejs3/usage-regenerator-used-async/output.mjs

@@ -2,14 +2,27 @@ import "core-js/modules/es.object.to-string";
 import "core-js/modules/es.promise";
 import "regenerator-runtime/runtime";
 
+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 regeneratorRuntime.async(function a$(_context) {
-    while (1) {
-      switch (_context.prev = _context.next) {
-        case 0:
-        case "end":
-          return _context.stop();
+  return _a.apply(this, arguments);
+}
+
+function _a() {
+  _a = _asyncToGenerator(
+  /*#__PURE__*/
+  regeneratorRuntime.mark(function _callee() {
+    return regeneratorRuntime.wrap(function _callee$(_context) {
+      while (1) {
+        switch (_context.prev = _context.next) {
+          case 0:
+          case "end":
+            return _context.stop();
+        }
       }
-    }
-  });
+    }, _callee);
+  }));
+  return _a.apply(this, arguments);
 }

packages/babel-preset-env/test/fixtures/debug/corejs-without-usebuiltins/stdout.txt

@@ -30,6 +30,7 @@ Using plugins:
   transform-new-target {}
   transform-regenerator {}
   transform-exponentiation-operator {}
+  transform-async-to-generator {}
   proposal-async-generator-functions {}
   proposal-object-rest-spread {}
   proposal-unicode-property-regex {}

packages/babel-preset-env/test/fixtures/debug/entry-corejs2-android/stdout.txt

@@ -30,6 +30,7 @@ Using plugins:
   transform-new-target { "android":"4" }
   transform-regenerator { "android":"4" }
   transform-exponentiation-operator { "android":"4" }
+  transform-async-to-generator { "android":"4" }
   proposal-async-generator-functions { "android":"4" }
   proposal-object-rest-spread { "android":"4" }
   proposal-unicode-property-regex { "android":"4" }

packages/babel-preset-env/test/fixtures/debug/entry-corejs2-electron/stdout.txt

@@ -25,6 +25,7 @@ Using plugins:
   transform-block-scoping { "electron":"0.36" }
   transform-regenerator { "electron":"0.36" }
   transform-exponentiation-operator { "electron":"0.36" }
+  transform-async-to-generator { "electron":"0.36" }
   proposal-async-generator-functions { "electron":"0.36" }
   proposal-object-rest-spread { "electron":"0.36" }
   proposal-unicode-property-regex { "electron":"0.36" }

packages/babel-preset-env/test/fixtures/debug/entry-corejs2-force-all-transforms/stdout.txt

@@ -30,6 +30,7 @@ Using plugins:
   transform-new-target {}
   transform-regenerator {}
   transform-exponentiation-operator {}
+  transform-async-to-generator {}
   proposal-async-generator-functions { "chrome":"55" }
   proposal-object-rest-spread { "chrome":"55" }
   proposal-unicode-property-regex { "chrome":"55" }

packages/babel-preset-env/test/fixtures/debug/entry-corejs2-proposals/stdout.txt

@@ -28,6 +28,7 @@ Using plugins:
   transform-new-target {}
   transform-regenerator {}
   transform-exponentiation-operator {}
+  transform-async-to-generator {}
   proposal-async-generator-functions {}
   proposal-object-rest-spread {}
   proposal-unicode-property-regex {}

packages/babel-preset-env/test/fixtures/debug/entry-corejs2-shippedProposals/stdout.txt

@@ -28,6 +28,7 @@ Using plugins:
   transform-new-target {}
   transform-regenerator {}
   transform-exponentiation-operator {}
+  transform-async-to-generator {}
   proposal-async-generator-functions {}
   proposal-object-rest-spread {}
   proposal-unicode-property-regex {}

packages/babel-preset-env/test/fixtures/debug/entry-corejs2-specific-targets/stdout.txt

@@ -35,6 +35,7 @@ Using plugins:
   transform-new-target { "edge":"13", "ie":"10", "ios":"9", "safari":"7" }
   transform-regenerator { "firefox":"49", "ie":"10", "ios":"9", "safari":"7" }
   transform-exponentiation-operator { "edge":"13", "firefox":"49", "ie":"10", "ios":"9", "safari":"7" }
+  transform-async-to-generator { "chrome":"54", "edge":"13", "firefox":"49", "ie":"10", "ios":"9", "safari":"7" }
   proposal-async-generator-functions { "chrome":"54", "edge":"13", "firefox":"49", "ie":"10", "ios":"9", "safari":"7" }
   proposal-object-rest-spread { "chrome":"54", "edge":"13", "firefox":"49", "ie":"10", "ios":"9", "safari":"7" }
   proposal-unicode-property-regex { "chrome":"54", "edge":"13", "firefox":"49", "ie":"10", "ios":"9", "safari":"7" }

packages/babel-preset-env/test/fixtures/debug/entry-corejs2-versions-decimals/stdout.txt

@@ -41,6 +41,7 @@ Using plugins:
   transform-new-target { "ie":"10" }
   transform-regenerator { "electron":"0.36", "ie":"10" }
   transform-exponentiation-operator { "electron":"0.36", "ie":"10", "node":"6.1" }
+  transform-async-to-generator { "chrome":"54", "electron":"0.36", "ie":"10", "node":"6.1" }
   proposal-async-generator-functions { "chrome":"54", "electron":"0.36", "ie":"10", "node":"6.1" }
   proposal-object-rest-spread { "chrome":"54", "electron":"0.36", "ie":"10", "node":"6.1" }
   proposal-unicode-property-regex { "chrome":"54", "electron":"0.36", "ie":"10", "node":"6.1" }

packages/babel-preset-env/test/fixtures/debug/entry-corejs2-versions-strings/stdout.txt

@@ -32,6 +32,7 @@ Using plugins:
   transform-new-target { "ie":"10" }
   transform-regenerator { "ie":"10" }
   transform-exponentiation-operator { "ie":"10", "node":"6.10" }
+  transform-async-to-generator { "chrome":"54", "ie":"10", "node":"6.10" }
   proposal-async-generator-functions { "chrome":"54", "ie":"10", "node":"6.10" }
   proposal-object-rest-spread { "chrome":"54", "ie":"10", "node":"6.10" }
   proposal-unicode-property-regex { "chrome":"54", "ie":"10", "node":"6.10" }

packages/babel-preset-env/test/fixtures/debug/entry-corejs2/stdout.txt

@@ -32,6 +32,7 @@ Using plugins:
   transform-new-target { "ie":"10" }
   transform-regenerator { "ie":"10" }
   transform-exponentiation-operator { "ie":"10", "node":"6" }
+  transform-async-to-generator { "chrome":"54", "ie":"10", "node":"6" }
   proposal-async-generator-functions { "chrome":"54", "ie":"10", "node":"6" }
   proposal-object-rest-spread { "chrome":"54", "ie":"10", "node":"6" }
   proposal-unicode-property-regex { "chrome":"54", "ie":"10", "node":"6" }

packages/babel-preset-env/test/fixtures/debug/entry-corejs3-all/stdout.txt

@@ -28,6 +28,7 @@ Using plugins:
   transform-new-target {}
   transform-regenerator {}
   transform-exponentiation-operator {}
+  transform-async-to-generator {}
   proposal-async-generator-functions {}
   proposal-object-rest-spread {}
   proposal-unicode-property-regex {}

packages/babel-preset-env/test/fixtures/debug/entry-corejs3-android/stdout.txt

@@ -30,6 +30,7 @@ Using plugins:
   transform-new-target { "android":"4" }
   transform-regenerator { "android":"4" }
   transform-exponentiation-operator { "android":"4" }
+  transform-async-to-generator { "android":"4" }
   proposal-async-generator-functions { "android":"4" }
   proposal-object-rest-spread { "android":"4" }
   proposal-unicode-property-regex { "android":"4" }

packages/babel-preset-env/test/fixtures/debug/entry-corejs3-babel-polyfill/stdout.txt

@@ -28,6 +28,7 @@ Using plugins:
   transform-new-target {}
   transform-regenerator {}
   transform-exponentiation-operator {}
+  transform-async-to-generator {}
   proposal-async-generator-functions {}
   proposal-object-rest-spread {}
   proposal-unicode-property-regex {}

packages/babel-preset-env/test/fixtures/debug/entry-corejs3-electron/stdout.txt

@@ -25,6 +25,7 @@ Using plugins:
   transform-block-scoping { "electron":"0.36" }
   transform-regenerator { "electron":"0.36" }
   transform-exponentiation-operator { "electron":"0.36" }
+  transform-async-to-generator { "electron":"0.36" }
   proposal-async-generator-functions { "electron":"0.36" }
   proposal-object-rest-spread { "electron":"0.36" }
   proposal-unicode-property-regex { "electron":"0.36" }

packages/babel-preset-env/test/fixtures/debug/entry-corejs3-es-proposals/stdout.txt

@@ -28,6 +28,7 @@ Using plugins:
   transform-new-target {}
   transform-regenerator {}
   transform-exponentiation-operator {}
+  transform-async-to-generator {}
   proposal-async-generator-functions {}
   proposal-object-rest-spread {}
   proposal-unicode-property-regex {}

packages/babel-preset-env/test/fixtures/debug/entry-corejs3-es/stdout.txt

@@ -28,6 +28,7 @@ Using plugins:
   transform-new-target {}
   transform-regenerator {}
   transform-exponentiation-operator {}
+  transform-async-to-generator {}
   proposal-async-generator-functions {}
   proposal-object-rest-spread {}
   proposal-unicode-property-regex {}

packages/babel-preset-env/test/fixtures/debug/entry-corejs3-force-all-transforms/stdout.txt

@@ -30,6 +30,7 @@ Using plugins:
   transform-new-target {}
   transform-regenerator {}
   transform-exponentiation-operator {}
+  transform-async-to-generator {}
   proposal-async-generator-functions { "chrome":"55" }
   proposal-object-rest-spread { "chrome":"55" }
   proposal-unicode-property-regex { "chrome":"55" }

packages/babel-preset-env/test/fixtures/debug/entry-corejs3-proposals/stdout.txt

@@ -28,6 +28,7 @@ Using plugins:
   transform-new-target {}
   transform-regenerator {}
   transform-exponentiation-operator {}
+  transform-async-to-generator {}
   proposal-async-generator-functions {}
   proposal-object-rest-spread {}
   proposal-unicode-property-regex {}

packages/babel-preset-env/test/fixtures/debug/entry-corejs3-specific-entries/stdout.txt

@@ -28,6 +28,7 @@ Using plugins:
   transform-new-target {}
   transform-regenerator {}
   transform-exponentiation-operator {}
+  transform-async-to-generator {}
   proposal-async-generator-functions {}
   proposal-object-rest-spread {}
   proposal-unicode-property-regex {}

packages/babel-preset-env/test/fixtures/debug/entry-corejs3-specific-targets/stdout.txt

@@ -35,6 +35,7 @@ Using plugins:
   transform-new-target { "edge":"13", "ie":"10", "ios":"9", "safari":"7" }
   transform-regenerator { "firefox":"49", "ie":"10", "ios":"9", "safari":"7" }
   transform-exponentiation-operator { "edge":"13", "firefox":"49", "ie":"10", "ios":"9", "safari":"7" }
+  transform-async-to-generator { "chrome":"54", "edge":"13", "firefox":"49", "ie":"10", "ios":"9", "safari":"7" }
   proposal-async-generator-functions { "chrome":"54", "edge":"13", "firefox":"49", "ie":"10", "ios":"9", "safari":"7" }
   proposal-object-rest-spread { "chrome":"54", "edge":"13", "firefox":"49", "ie":"10", "ios":"9", "safari":"7" }
   proposal-unicode-property-regex { "chrome":"54", "edge":"13", "firefox":"49", "ie":"10", "ios":"9", "safari":"7" }

packages/babel-preset-env/test/fixtures/debug/entry-corejs3-stable/stdout.txt

@@ -28,6 +28,7 @@ Using plugins:
   transform-new-target {}
   transform-regenerator {}
   transform-exponentiation-operator {}
+  transform-async-to-generator {}
   proposal-async-generator-functions {}
   proposal-object-rest-spread {}
   proposal-unicode-property-regex {}

packages/babel-preset-env/test/fixtures/debug/entry-corejs3-stage/stdout.txt

@@ -28,6 +28,7 @@ Using plugins:
   transform-new-target {}
   transform-regenerator {}
   transform-exponentiation-operator {}
+  transform-async-to-generator {}
   proposal-async-generator-functions {}
   proposal-object-rest-spread {}
   proposal-unicode-property-regex {}

packages/babel-preset-env/test/fixtures/debug/entry-corejs3-versions-decimals/stdout.txt

@@ -41,6 +41,7 @@ Using plugins:
   transform-new-target { "ie":"10" }
   transform-regenerator { "electron":"0.36", "ie":"10" }
   transform-exponentiation-operator { "electron":"0.36", "ie":"10", "node":"6.1" }
+  transform-async-to-generator { "chrome":"54", "electron":"0.36", "ie":"10", "node":"6.1" }
   proposal-async-generator-functions { "chrome":"54", "electron":"0.36", "ie":"10", "node":"6.1" }
   proposal-object-rest-spread { "chrome":"54", "electron":"0.36", "ie":"10", "node":"6.1" }
   proposal-unicode-property-regex { "chrome":"54", "electron":"0.36", "ie":"10", "node":"6.1" }

packages/babel-preset-env/test/fixtures/debug/entry-corejs3-versions-strings-minor-3.0/stdout.txt

@@ -32,6 +32,7 @@ Using plugins:
   transform-new-target { "ie":"10" }
   transform-regenerator { "ie":"10" }
   transform-exponentiation-operator { "ie":"10", "node":"6.10" }
+  transform-async-to-generator { "chrome":"54", "ie":"10", "node":"6.10" }
   proposal-async-generator-functions { "chrome":"54", "ie":"10", "node":"6.10" }
   proposal-object-rest-spread { "chrome":"54", "ie":"10", "node":"6.10" }
   proposal-unicode-property-regex { "chrome":"54", "ie":"10", "node":"6.10" }

packages/babel-preset-env/test/fixtures/debug/entry-corejs3-versions-strings-minor-3.1/stdout.txt

@@ -32,6 +32,7 @@ Using plugins:
   transform-new-target { "ie":"10" }
   transform-regenerator { "ie":"10" }
   transform-exponentiation-operator { "ie":"10", "node":"6.10" }
+  transform-async-to-generator { "chrome":"54", "ie":"10", "node":"6.10" }
   proposal-async-generator-functions { "chrome":"54", "ie":"10", "node":"6.10" }
   proposal-object-rest-spread { "chrome":"54", "ie":"10", "node":"6.10" }
   proposal-unicode-property-regex { "chrome":"54", "ie":"10", "node":"6.10" }

packages/babel-preset-env/test/fixtures/debug/entry-corejs3-versions-strings/stdout.txt

@@ -32,6 +32,7 @@ Using plugins:
   transform-new-target { "ie":"10" }
   transform-regenerator { "ie":"10" }
   transform-exponentiation-operator { "ie":"10", "node":"6.10" }
+  transform-async-to-generator { "chrome":"54", "ie":"10", "node":"6.10" }
   proposal-async-generator-functions { "chrome":"54", "ie":"10", "node":"6.10" }
   proposal-object-rest-spread { "chrome":"54", "ie":"10", "node":"6.10" }
   proposal-unicode-property-regex { "chrome":"54", "ie":"10", "node":"6.10" }

packages/babel-preset-env/test/fixtures/debug/entry-corejs3-web/stdout.txt

@@ -28,6 +28,7 @@ Using plugins:
   transform-new-target {}
   transform-regenerator {}
   transform-exponentiation-operator {}
+  transform-async-to-generator {}
   proposal-async-generator-functions {}
   proposal-object-rest-spread {}
   proposal-unicode-property-regex {}