Implement async-do-expressions transform (#13117)

Co-authored-by: Brian Ng <bng412@gmail.com>

packages/babel-plugin-proposal-async-do-expressions/.npmignore

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+src
+test
+*.log

packages/babel-plugin-proposal-async-do-expressions/README.md

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+# @babel/plugin-proposal-async-do-expressions
+
+> Transforms async do expressions to ES2021
+
+See our website [@babel/plugin-proposal-async-do-expressions](https://babeljs.io/docs/en/babel-plugin-proposal-async-do-expressions) for more information.
+
+## Install
+
+Using npm:
+
+```sh
+npm install --save-dev @babel/plugin-proposal-async-do-expressions
+```
+
+or using yarn:
+
+```sh
+yarn add @babel/plugin-proposal-async-do-expressions --dev
+```

packages/babel-plugin-proposal-async-do-expressions/package.json

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+{
+  "name": "@babel/plugin-proposal-async-do-expressions",
+  "version": "7.13.11",
+  "description": "Transform async do expressions to ES2021",
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/babel/babel.git",
+    "directory": "packages/babel-plugin-proposal-async-do-expressions"
+  },
+  "license": "MIT",
+  "publishConfig": {
+    "access": "public"
+  },
+  "main": "./lib/index.js",
+  "exports": {
+    ".": "./lib/index.js"
+  },
+  "keywords": [
+    "babel-plugin"
+  ],
+  "dependencies": {
+    "@babel/helper-hoist-variables": "workspace:^7.13.0",
+    "@babel/helper-plugin-utils": "workspace:^7.13.0",
+    "@babel/plugin-syntax-async-do-expressions": "workspace:^7.13.0"
+  },
+  "peerDependencies": {
+    "@babel/core": "^7.13.0"
+  },
+  "devDependencies": {
+    "@babel/core": "workspace:*",
+    "@babel/helper-plugin-test-runner": "workspace:*",
+    "@babel/traverse": "workspace:*",
+    "@babel/types": "workspace:*"
+  },
+  "homepage": "https://babel.dev/docs/en/next/babel-plugin-proposal-async-do-expressions"
+}

packages/babel-plugin-proposal-async-do-expressions/src/index.ts

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+import { declare } from "@babel/helper-plugin-utils";
+import syntaxAsyncDoExpressions from "@babel/plugin-syntax-async-do-expressions";
+import hoistVariables from "@babel/helper-hoist-variables";
+import type * as t from "@babel/types";
+import type { NodePath } from "@babel/traverse";
+
+export default declare(({ types: t, assertVersion }) => {
+  assertVersion("^7.13.0");
+
+  return {
+    name: "proposal-async-do-expressions",
+    inherits: syntaxAsyncDoExpressions,
+    visitor: {
+      DoExpression: {
+        exit(path: NodePath<t.DoExpression>) {
+          if (!path.is("async")) {
+            // non-async do expressions are handled by proposal-do-expressions
+            return;
+          }
+          const { scope } = path;
+          // Hoist variable declaration to containing function scope
+          // `async do { var x = 1; x }` -> `var x; (async() => { x = 1; return x })()`
+          hoistVariables(
+            path,
+            (id: t.Identifier) => {
+              scope.push({ id: t.cloneNode(id) });
+            },
+            "var",
+          );
+          const bodyPath = path.get("body");
+
+          // add implicit returns to all ending expression statements
+          const completionRecords = bodyPath.getCompletionRecords();
+
+          for (const p of completionRecords) {
+            if (p.isExpressionStatement()) {
+              p.replaceWith(t.returnStatement(p.node.expression));
+            }
+          }
+
+          path.replaceWith(
+            t.callExpression(
+              t.arrowFunctionExpression([], bodyPath.node, /* async */ true),
+              [],
+            ),
+          );
+        },
+      },
+    },
+  };
+});

packages/babel-plugin-proposal-async-do-expressions/test/fixtures/async-do-expressions/basic/exec.js

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+const x = async do { 21 + 21 };
+
+expect(x).toBeInstanceOf(Promise);
+x.then((v) => expect(v).toBe(42)).catch(err => { throw err });

packages/babel-plugin-proposal-async-do-expressions/test/fixtures/async-do-expressions/basic/input.js

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+const x = async do { 21 + 21 };

packages/babel-plugin-proposal-async-do-expressions/test/fixtures/async-do-expressions/basic/output.js

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+const x = (async () => {
+  return 21 + 21;
+})();

packages/babel-plugin-proposal-async-do-expressions/test/fixtures/async-do-expressions/empty-statement-list/input.js

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+async do {}

packages/babel-plugin-proposal-async-do-expressions/test/fixtures/async-do-expressions/empty-statement-list/output.js

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+(async () => {})();

packages/babel-plugin-proposal-async-do-expressions/test/fixtures/async-do-expressions/hoist-variables-assgined-in-sync-context/exec.js

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+const x = async do { var y = 21; y + y }
+
+expect(y).toBe(21);
+x.then((resolved) => {
+  expect(resolved).toBe(42);
+}).catch(err => { throw err });

packages/babel-plugin-proposal-async-do-expressions/test/fixtures/async-do-expressions/hoist-variables-assgined-in-sync-context/input.js

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+const x = async do { var y = 21; y + y }

packages/babel-plugin-proposal-async-do-expressions/test/fixtures/async-do-expressions/hoist-variables-assgined-in-sync-context/output.js

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+var y;
+
+const x = (async () => {
+  y = 21;
+  return y + y;
+})();

packages/babel-plugin-proposal-async-do-expressions/test/fixtures/async-do-expressions/hoist-variables-assigned-in-async-context/exec.js

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+const x = async do { await Promise.resolve(); var y = 21; y + y }
+
+expect(y).toBe(undefined);
+x.then((resolved) => {
+  expect(y).toBe(21);
+  expect(resolved).toBe(42);
+}).catch(err => { throw err });

packages/babel-plugin-proposal-async-do-expressions/test/fixtures/async-do-expressions/hoist-variables-assigned-in-async-context/input.js

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+const x = async do { await Promise.resolve(); var y = 21; y + y }

packages/babel-plugin-proposal-async-do-expressions/test/fixtures/async-do-expressions/hoist-variables-assigned-in-async-context/output.js

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+var y;
+
+const x = (async () => {
+  await Promise.resolve();
+  y = 21;
+  return y + y;
+})();

packages/babel-plugin-proposal-async-do-expressions/test/fixtures/async-do-expressions/lexical-declaration/exec.js

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+const x = async do { let x = 21; x + x };
+
+expect(x).toBeInstanceOf(Promise);
+x.then((v) => expect(v).toBe(42)).catch(err => { throw err });

packages/babel-plugin-proposal-async-do-expressions/test/fixtures/async-do-expressions/lexical-declaration/input.js

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+const x = async do { let x = 21; x + x };

packages/babel-plugin-proposal-async-do-expressions/test/fixtures/async-do-expressions/lexical-declaration/output.js

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+const x = (async () => {
+  let x = 21;
+  return x + x;
+})();
+

packages/babel-plugin-proposal-async-do-expressions/test/fixtures/async-do-expressions/throw-statement/exec.js

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+const x = async do { throw new Error("sync") };
+
+expect(x).toBeInstanceOf(Promise);
+x.then(() => { throw new Error("expected an error: sync is thrown.") })
+.catch(err => { expect(err.message).toEqual("sync") });

packages/babel-plugin-proposal-async-do-expressions/test/fixtures/async-do-expressions/throw-statement/input.js

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+const x = async do { throw new Error("sync") };

packages/babel-plugin-proposal-async-do-expressions/test/fixtures/async-do-expressions/throw-statement/output.js

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+const x = (async () => {
+  throw new Error("sync");
+})();

packages/babel-plugin-proposal-async-do-expressions/test/fixtures/options.json

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+{
+  "plugins": ["proposal-async-do-expressions"],
+  "minNodeVersion": "8.0.0"
+}

packages/babel-plugin-proposal-async-do-expressions/test/fixtures/sync-do-expressions/basic/input.js

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+// sync do expressions are not handled by this plugin
+(do {});

packages/babel-plugin-proposal-async-do-expressions/test/fixtures/sync-do-expressions/basic/options.json

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+{
+  "plugins": ["proposal-async-do-expressions"],
+  "minNodeVersion": "6.0.0"
+}

packages/babel-plugin-proposal-async-do-expressions/test/fixtures/sync-do-expressions/basic/output.js

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+// sync do expressions are not handled by this plugin
+(do {});

packages/babel-plugin-proposal-async-do-expressions/test/index.js

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+import runner from "@babel/helper-plugin-test-runner";
+
+runner(import.meta.url);

yarn.lock

@@ -1050,6 +1050,22 @@ __metadata:
   languageName: unknown
   linkType: soft
 
+"@babel/plugin-proposal-async-do-expressions@workspace:packages/babel-plugin-proposal-async-do-expressions":
+  version: 0.0.0-use.local
+  resolution: "@babel/plugin-proposal-async-do-expressions@workspace:packages/babel-plugin-proposal-async-do-expressions"
+  dependencies:
+    "@babel/core": "workspace:*"
+    "@babel/helper-hoist-variables": "workspace:^7.13.0"
+    "@babel/helper-plugin-test-runner": "workspace:*"
+    "@babel/helper-plugin-utils": "workspace:^7.13.0"
+    "@babel/plugin-syntax-async-do-expressions": "workspace:^7.13.0"
+    "@babel/traverse": "workspace:*"
+    "@babel/types": "workspace:*"
+  peerDependencies:
+    "@babel/core": ^7.13.0
+  languageName: unknown
+  linkType: soft
+
 "@babel/plugin-proposal-async-generator-functions@npm:^7.13.5":
   version: 7.13.5
   resolution: "@babel/plugin-proposal-async-generator-functions@npm:7.13.5"
@@ -1537,7 +1553,7 @@ __metadata:
   languageName: unknown
   linkType: soft
 
-"@babel/plugin-syntax-async-do-expressions@workspace:packages/babel-plugin-syntax-async-do-expressions":
+"@babel/plugin-syntax-async-do-expressions@workspace:^7.13.0, @babel/plugin-syntax-async-do-expressions@workspace:packages/babel-plugin-syntax-async-do-expressions":
   version: 0.0.0-use.local
   resolution: "@babel/plugin-syntax-async-do-expressions@workspace:packages/babel-plugin-syntax-async-do-expressions"
   dependencies: