feat: add support for converting optional chaining to regular chaining (

#3891)

* feat: add support for converting optional chaining to regular chaining

* chore: linting fixes

packages/typeless-sample-bot/src/samples.ts

@@ -23,6 +23,7 @@ import path from 'node:path';
 import {typescript as presetTypescript} from './preset-loader.js';
 import importToRequire from './transforms/import-to-require.js';
 import nullCoalescing from './transforms/null-coalescing.js';
+import optionalChaining from './transforms/optional-chaining.js';
 import {addComments} from './transforms/add-comments.js';
 
 // Converts an async iterable into an array of the same type.
@@ -85,7 +86,7 @@ export async function* filterByContents(
 // the transform process.
 const babelConfig = {
   presets: [[presetTypescript, {}]],
-  plugins: [[importToRequire], [nullCoalescing]],
+  plugins: [[importToRequire], [nullCoalescing], [optionalChaining]],
   parserOpts: {} as babel.ParserOptions,
   generatorOpts: {
     // Ensures that Babel keeps newlines so that comments end up

packages/typeless-sample-bot/src/transforms/optional-chaining.ts

@@ -0,0 +1,48 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import * as Babel from '@babel/types';
+import {NodePathSingle, VisitorPlugin} from './babel.js';
+
+// Because optional chaining is still a proposal in many versions of Node,
+// go ahead and convert it to plain '.'. It should work in TypeScript.
+export default function optionalChaining(): VisitorPlugin {
+  return {
+    visitor: {
+      OptionalCallExpression(path: NodePathSingle) {
+        const node = path.node as Babel.OptionalCallExpression;
+        path.replaceWith(Babel.callExpression(node.callee, node.arguments));
+      },
+      OptionalMemberExpression(path: NodePathSingle) {
+        const node = path.node as Babel.OptionalMemberExpression;
+        path.replaceWith(
+          Babel.memberExpression(
+            node.object,
+            node.property,
+            node.computed,
+            node.optional
+          )
+        );
+      },
+      LogicalExpression(path: NodePathSingle) {
+        const node = path.node as Babel.LogicalExpression;
+        if (node.operator === '??') {
+          path.replaceWith(
+            Babel.logicalExpression('||', node.left, node.right)
+          );
+        }
+      },
+    },
+  };
+}

packages/typeless-sample-bot/test/fixtures/folder/listenForAvroRecords.ts

@@ -89,6 +89,8 @@ function listenForAvroRecords(subscriptionNameOrId: string, timeout: number) {
     subscription.removeListener('message', messageHandler);
     console.log(`${messageCount} message(s) received.`);
   }, timeout * 1000);
+
+  use?.optional?.chaining?.();
 }
 // [END pubsub_subscribe_avro_records]