Fix compiling async arrows in uncompiled class fields

packages/babel-helper-wrap-function/src/index.ts

@@ -6,19 +6,39 @@ import {
   callExpression,
   functionExpression,
   isAssignmentPattern,
+  isFunctionDeclaration,
   isRestElement,
   returnStatement,
 } from "@babel/types";
 import type * as t from "@babel/types";
 
+type ExpressionWrapperBuilder<ExtraBody extends t.Node[]> = (
+  replacements?: Parameters<ReturnType<typeof template.expression>>[0],
+) => t.CallExpression & {
+  callee: t.FunctionExpression & {
+    body: {
+      body: [
+        t.VariableDeclaration & {
+          declarations: [
+            { init: t.FunctionExpression | t.ArrowFunctionExpression },
+          ];
+        },
+        ...ExtraBody,
+      ];
+    };
+  };
+};
+
 const buildAnonymousExpressionWrapper = template.expression(`
   (function () {
     var REF = FUNCTION;
     return function NAME(PARAMS) {
       return REF.apply(this, arguments);
     };
   })()
-`);
+`) as ExpressionWrapperBuilder<
+  [t.ReturnStatement & { argument: t.FunctionExpression }]
+>;
 
 const buildNamedExpressionWrapper = template.expression(`
   (function () {
@@ -28,7 +48,9 @@ const buildNamedExpressionWrapper = template.expression(`
     }
     return NAME;
   })()
-`);
+`) as ExpressionWrapperBuilder<
+  [t.FunctionDeclaration, t.ReturnStatement & { argument: t.Identifier }]
+>;
 
 const buildDeclarationWrapper = template.statements(`
   function NAME(PARAMS) { return REF.apply(this, arguments); }
@@ -72,28 +94,23 @@ function plainFunction(
   noNewArrows: boolean,
   ignoreFunctionLength: boolean,
 ) {
-  const node = path.node;
-  const isDeclaration = path.isFunctionDeclaration();
-  // @ts-expect-error id is not in ArrowFunctionExpression
-  const functionId = node.id;
-  const wrapper = isDeclaration
-    ? buildDeclarationWrapper
-    : functionId
-    ? buildNamedExpressionWrapper
-    : buildAnonymousExpressionWrapper;
-
+  let functionId = null;
+  let node;
   if (path.isArrowFunctionExpression()) {
-    path.arrowFunctionToExpression({ noNewArrows });
+    path = path.arrowFunctionToExpression({ noNewArrows });
+    node = path.node as t.FunctionDeclaration | t.FunctionExpression;
+  } else {
+    node = path.node as t.FunctionDeclaration | t.FunctionExpression;
   }
-  // @ts-expect-error node is FunctionDeclaration|FunctionExpression
-  node.id = null;
 
-  if (isDeclaration) {
-    node.type = "FunctionExpression";
-  }
+  const isDeclaration = isFunctionDeclaration(node);
+
+  functionId = node.id;
+  node.id = null;
+  node.type = "FunctionExpression";
 
   const built = callExpression(callId, [
-    node as Exclude<t.Function, t.Method | t.FunctionDeclaration>,
+    node as Exclude<typeof node, t.FunctionDeclaration>,
   ]);
 
   const params: t.Identifier[] = [];
@@ -104,34 +121,35 @@ function plainFunction(
     params.push(path.scope.generateUidIdentifier("x"));
   }
 
-  const container = wrapper({
+  const wrapperArgs = {
     NAME: functionId || null,
     REF: path.scope.generateUidIdentifier(functionId ? functionId.name : "ref"),
     FUNCTION: built,
     PARAMS: params,
-  });
+  };
 
   if (isDeclaration) {
-    path.replaceWith((container as t.Statement[])[0]);
-    path.insertAfter((container as t.Statement[])[1]);
+    const container = buildDeclarationWrapper(wrapperArgs);
+    path.replaceWith(container[0]);
+    path.insertAfter(container[1]);
   } else {
-    // @ts-expect-error todo(flow->ts) separate `wrapper` for `isDeclaration` and `else` branches
-    const retFunction = container.callee.body.body[1].argument;
-    if (!functionId) {
+    let container;
+
+    if (functionId) {
+      container = buildNamedExpressionWrapper(wrapperArgs);
+    } else {
+      container = buildAnonymousExpressionWrapper(wrapperArgs);
+
+      const returnFn = container.callee.body.body[1].argument;
       nameFunction({
-        node: retFunction,
+        node: returnFn,
         parent: path.parent,
         scope: path.scope,
       });
+      functionId = returnFn.id;
     }
 
-    if (
-      !retFunction ||
-      retFunction.id ||
-      (!ignoreFunctionLength && params.length)
-    ) {
-      // we have an inferred function id or params so we need this wrapper
-      // @ts-expect-error todo(flow->ts) separate `wrapper` for `isDeclaration` and `else` branches
+    if (functionId || (!ignoreFunctionLength && params.length)) {
       path.replaceWith(container);
     } else {
       // we can omit this wrapper as the conditions it protects for do not apply

packages/babel-plugin-transform-async-to-generator/test/fixtures/assumption-newableArrowFunctions-false/basic/output.js → packages/babel-plugin-transform-async-to-generator/test/fixtures/assumption-noNewArrows-false/basic/output.js

@@ -4,4 +4,4 @@ var _this = this;
 babelHelpers.asyncToGenerator(function* () {
   babelHelpers.newArrowCheck(this, _this);
   return 2;
-});
+}).bind(this);

packages/babel-plugin-transform-async-to-generator/test/fixtures/regression/in-uncompiled-class-fields/input.js

@@ -0,0 +1,8 @@
+// Angular needs to alwys compile async functions, even if
+// the targets support class fields.
+// https://github.com/babel/babel/issues/14749
+
+class A {
+  a = async () => this;
+  b = async (x, y, z) => this;
+}

packages/babel-plugin-transform-async-to-generator/test/fixtures/regression/in-uncompiled-class-fields/output.js

@@ -0,0 +1,25 @@
+// Angular needs to alwys compile async functions, even if
+// the targets support class fields.
+// https://github.com/babel/babel/issues/14749
+class A {
+  a = (() => {
+    var _this = this;
+
+    return babelHelpers.asyncToGenerator(function* () {
+      return _this;
+    });
+  })();
+  b = (() => {
+    var _this2 = this;
+
+    return function () {
+      var _ref2 = babelHelpers.asyncToGenerator(function* (x, y, z) {
+        return _this2;
+      });
+
+      return function (_x, _x2, _x3) {
+        return _ref2.apply(this, arguments);
+      };
+    }();
+  })();
+}

packages/babel-traverse/src/path/conversion.ts

@@ -135,6 +135,13 @@ export function unwrapFunctionEnvironment(this: NodePath) {
   hoistFunctionEnvironment(this);
 }
 
+function setType<N extends t.Node, T extends N["type"]>(
+  path: NodePath<N>,
+  type: T,
+): asserts path is NodePath<Extract<N, { type: T }>> {
+  path.node.type = type;
+}
+
 /**
  * Convert a given arrow function into a normal ES5 function expression.
  */
@@ -151,7 +158,7 @@ export function arrowFunctionToExpression(
     specCompliant?: boolean | void;
     noNewArrows?: boolean;
   } = {},
-) {
+): NodePath<Exclude<t.Function, t.Method | t.ArrowFunctionExpression>> {
   if (!this.isArrowFunctionExpression()) {
     throw (this as NodePath).buildCodeFrameError(
       "Cannot convert non-arrow function to a function expression.",
@@ -166,7 +173,8 @@ export function arrowFunctionToExpression(
 
   // @ts-expect-error TS requires explicit fn type annotation
   fn.ensureBlock();
-  fn.node.type = "FunctionExpression";
+  setType(fn, "FunctionExpression");
+
   if (!noNewArrows) {
     const checkBinding = thisBinding
       ? null
@@ -178,7 +186,7 @@ export function arrowFunctionToExpression(
       });
     }
 
-    (fn.get("body") as NodePath<t.BlockStatement>).unshiftContainer(
+    fn.get("body").unshiftContainer(
       "body",
       expressionStatement(
         callExpression(this.hub.addHelper("newArrowCheck"), [
@@ -200,7 +208,11 @@ export function arrowFunctionToExpression(
         [checkBinding ? identifier(checkBinding.name) : thisExpression()],
       ),
     );
+
+    return fn.get("callee.object");
   }
+
+  return fn;
 }
 
 const getSuperCallsVisitor = mergeVisitors<{