Await nullish async disposable

packages/babel-helpers/src/helpers-generated.ts

@@ -188,10 +188,10 @@ export default Object.freeze({
     "7.22.0",
     'export default function _using(o,n,e){if(null==n)return n;if(Object(n)!==n)throw new TypeError("using declarations can only be used with objects, functions, null, or undefined.");if(e)var r=n[Symbol.asyncDispose||Symbol.for("Symbol.asyncDispose")];if(null==r&&(r=n[Symbol.dispose||Symbol.for("Symbol.dispose")]),"function"!=typeof r)throw new TypeError("Property [Symbol.dispose] is not a function.");return o.push({v:n,d:r,a:e}),n}',
   ),
-  // size: 891, gzip size: 466
+  // size: 922, gzip size: 481
   usingCtx: helper(
     "7.23.9",
-    'export default function _usingCtx(){var r="function"==typeof SuppressedError?SuppressedError:function(r,n){var e=Error();return e.name="SuppressedError",e.suppressed=n,e.error=r,e},n={},e=[];function using(r,n){if(null!=n){if(Object(n)!==n)throw new TypeError("using declarations can only be used with objects, functions, null, or undefined.");if(r)var o=n[Symbol.asyncDispose||Symbol.for("Symbol.asyncDispose")];if(null==o&&(o=n[Symbol.dispose||Symbol.for("Symbol.dispose")]),"function"!=typeof o)throw new TypeError("Property [Symbol.dispose] is not a function.");e.push({v:n,d:o,a:r})}return n}return{e:n,u:using.bind(null,!1),a:using.bind(null,!0),d:function(){var o=this.e;function next(){for(;r=e.pop();)try{var r,t=r.d.call(r.v);if(r.a)return Promise.resolve(t).then(next,err)}catch(r){return err(r)}if(o!==n)throw o}function err(e){return o=o!==n?new r(o,e):e,next()}return next()}}}',
+    'export default function _usingCtx(){var r="function"==typeof SuppressedError?SuppressedError:function(r,n){var e=Error();return e.name="SuppressedError",e.suppressed=n,e.error=r,e},n={},e=[];function using(r,n){if(null!=n){if(Object(n)!==n)throw new TypeError("using declarations can only be used with objects, functions, null, or undefined.");if(r)var o=n[Symbol.asyncDispose||Symbol.for("Symbol.asyncDispose")];if(null==o&&(o=n[Symbol.dispose||Symbol.for("Symbol.dispose")]),"function"!=typeof o)throw new TypeError("Property [Symbol.dispose] is not a function.");e.push({v:n,d:o,a:r})}else r&&e.push({d:n,a:r});return n}return{e:n,u:using.bind(null,!1),a:using.bind(null,!0),d:function(){var o=this.e;function next(){for(;r=e.pop();)try{var r,t=r.d&&r.d.call(r.v);if(r.a)return Promise.resolve(t).then(next,err)}catch(r){return err(r)}if(o!==n)throw o}function err(e){return o=o!==n?new r(o,e):e,next()}return next()}}}',
   ),
   // size: 1252, gzip size: 572
   wrapRegExp: helper(

packages/babel-helpers/src/helpers/usingCtx.ts

@@ -1,8 +1,8 @@
 /* @minVersion 7.23.9 */
 
 type Stack = {
-  v: any;
-  d: () => any;
+  v?: any;
+  d: null | undefined | (() => any);
   a: boolean;
 };
 
@@ -39,6 +39,9 @@ export default function _usingCtx() {
         throw new TypeError(`Property [Symbol.dispose] is not a function.`);
       }
       stack.push({ v: value, d: dispose, a: isAwait });
+    } else if (isAwait) {
+      // provide the nullish `value` as `d` for minification gain
+      stack.push({ d: value, a: isAwait });
     }
     return value;
   }
@@ -58,7 +61,7 @@ export default function _usingCtx() {
         while ((resource = stack.pop())) {
           try {
             var resource,
-              disposalResult = resource.d.call(resource.v);
+              disposalResult = resource.d && resource.d.call(resource.v);
             if (resource.a) {
               return Promise.resolve(disposalResult).then(next, err);
             }

packages/babel-plugin-proposal-explicit-resource-management/test/fixtures/exec-async/using-null-multiple.js

@@ -0,0 +1,25 @@
+return (async function () {
+  const log = [];
+
+  function disposable(name) {
+    return {
+      async [Symbol.dispose || Symbol.for("Symbol.dispose")]() {
+        log.push(name);
+      },
+    };
+  }
+
+  async function f() {
+    using y = disposable("y");
+    await using x = null;
+    log.push("f body");
+  }
+
+  const promise = f();
+
+  log.push("body");
+
+  await promise;
+
+  expect(log).toEqual(["f body", "body", "y"]);
+})();

packages/babel-plugin-proposal-explicit-resource-management/test/fixtures/exec-async/using-undefined-multiple.js

@@ -0,0 +1,25 @@
+return (async function () {
+  const log = [];
+
+  function disposable(name) {
+    return {
+      async [Symbol.dispose || Symbol.for("Symbol.dispose")]() {
+        log.push(name);
+      },
+    };
+  }
+
+  async function f() {
+    using y = disposable("y");
+    await using x = undefined;
+    log.push("f body");
+  }
+
+  const promise = f();
+
+  log.push("body");
+
+  await promise;
+
+  expect(log).toEqual(["f body", "body", "y"]);
+})();

packages/babel-runtime-corejs3/helpers/esm/usingCtx.js

@@ -22,7 +22,10 @@ export default function _usingCtx() {
         d: o,
         a: r
       });
-    }
+    } else r && _pushInstanceProperty(e).call(e, {
+      d: n,
+      a: r
+    });
     return n;
   }
   return {
@@ -34,7 +37,7 @@ export default function _usingCtx() {
       function next() {
         for (; r = e.pop();) try {
           var r,
-            t = r.d.call(r.v);
+            t = r.d && r.d.call(r.v);
           if (r.a) return _Promise.resolve(t).then(next, err);
         } catch (r) {
           return err(r);