feat(aws-cdk-lib): reduce load time of JavaScript library (#27217)

This change halves the load time of `require('aws-cdk-lib')`, from ~600ms to ~300ms on my machine. It also shaves ~8min off running all integ tests (again, on my machine).

It does this by making all loading of JavaScript modules lazy, so they are only loaded just before any symbols from them are actually accessed (instead of loading all modules at startup). This new automatic module replaces the previous manual effort to do something similar, in `lazy-index.ts`.

Note that this transformation (unfortunately) does not affect TypeScript compilation times: the TypeScript compiler is still going to read all `.d.ts` files. To improve interactive TypeScript performance, use `swc` or `ts-node` with type checking disabled. Fully type checking your application using `tsc` will take the amount of time it takes.

Turning this:

```js
const x = require("x");
module.exports.banana = function() {
  return x.hello();
}
```

Into this:

```js
var x = () => { var tmp = require("x"); x = () => tmp; return tmp; };
module.exports.banana = function () {
    return x().hello();
};
```

packages/@aws-cdk-testing/cli-integ/tests/init-javascript/init-javascript.integtest.ts

@@ -25,8 +25,10 @@ integTest('Test importing CDK from ESM', withTemporaryDirectory(withPackages(asy
 
   // Rewrite some files
   await fs.writeFile(path.join(context.integTestDir, 'new-entrypoint.mjs'), `
-// Test two styles of imports
-import { Stack, aws_sns as sns, aws_sns_subscriptions as subs, aws_sqs as sqs } from 'aws-cdk-lib';
+// Test multiple styles of imports
+import { Stack, aws_sns as sns } from 'aws-cdk-lib';
+import { SqsSubscription } from 'aws-cdk-lib/aws-sns-subscriptions';
+import * as sqs from 'aws-cdk-lib/aws-sqs';
 import * as cdk from 'aws-cdk-lib';
 
 class TestjsStack extends Stack {
@@ -39,7 +41,7 @@ class TestjsStack extends Stack {
 
     const topic = new sns.Topic(this, 'TestjsTopic');
 
-    topic.addSubscription(new subs.SqsSubscription(queue));
+    topic.addSubscription(new SqsSubscription(queue));
   }
 }
 

tools/@aws-cdk/lazify/lib/index.ts

@@ -159,7 +159,7 @@ export function transformFileContents(filename: string, contents: string, progre
         const module = require(file);
         const entries = Object.keys(module);
 
-        return entries.map((entry) =>
+        return entries.flatMap((entry) =>
           createModuleGetter(factory, entry, requiredModule, (mod) =>
             factory.createPropertyAccessExpression(mod, entry))
           );
@@ -212,25 +212,51 @@ function createAssignment(factory: ts.NodeFactory, name: string, expression: ts.
       expression));
 }
 
+/**
+ * Create an lazy getter for a particular value at the module level
+ *
+ * Since Node statically analyzes CommonJS modules to determine its exports
+ * (using the `cjs-module-lexer` module), we need to trick it into recognizing
+ * these exports as legitimate.
+ *
+ * We do that by generating one form it will recognize that doesn't do anything,
+ * in combination with a form that actually works, that doesn't disqualify the
+ * export name.
+ */
 function createModuleGetter(
   factory: ts.NodeFactory,
   exportName: string,
   moduleName: string,
   moduleFormatter: (x: ts.Expression) => ts.Expression,
 ) {
-  return factory.createExpressionStatement(factory.createCallExpression(
-    factory.createPropertyAccessExpression(factory.createIdentifier('Object'), factory.createIdentifier('defineProperty')),
-    undefined,
-    [
-      factory.createIdentifier('exports'),
-      factory.createStringLiteral(exportName),
-      factory.createObjectLiteralExpression([
-        factory.createPropertyAssignment('configurable', factory.createTrue()),
-        factory.createPropertyAssignment('get',
-          factory.createArrowFunction(undefined, undefined, [], undefined, undefined,
-            moduleFormatter(
-              factory.createCallExpression(factory.createIdentifier('require'), undefined, [factory.createStringLiteral(moduleName)])))),
-      ]),
-    ]
-  ));
+  return [
+    // exports.<name> = void 0;
+    factory.createExpressionStatement(factory.createBinaryExpression(
+      factory.createPropertyAccessExpression(
+        factory.createIdentifier('exports'),
+        factory.createIdentifier(exportName)),
+      ts.SyntaxKind.EqualsToken,
+      factory.createVoidZero())),
+    // Object.defineProperty(exports, "<n>" + "<ame>", { get: () =>  });
+    factory.createExpressionStatement(factory.createCallExpression(
+      factory.createPropertyAccessExpression(factory.createIdentifier('Object'), factory.createIdentifier('defineProperty')),
+      undefined,
+      [
+        factory.createIdentifier('exports'),
+        factory.createBinaryExpression(
+          factory.createStringLiteral(exportName.substring(0, 1)),
+          ts.SyntaxKind.PlusToken,
+          factory.createStringLiteral(exportName.substring(1)),
+        ),
+        factory.createObjectLiteralExpression([
+          factory.createPropertyAssignment('enumerable', factory.createTrue()),
+          factory.createPropertyAssignment('configurable', factory.createTrue()),
+          factory.createPropertyAssignment('get',
+            factory.createArrowFunction(undefined, undefined, [], undefined, undefined,
+              moduleFormatter(
+                factory.createCallExpression(factory.createIdentifier('require'), undefined, [factory.createStringLiteral(moduleName)])))),
+        ]),
+      ]
+    )
+  )];
 }

tools/@aws-cdk/lazify/package.json

@@ -20,7 +20,8 @@
     "@aws-cdk/cdk-build-tools": "0.0.0",
     "jest": "^29",
     "ts-jest": "^29",
-    "typescript": "^4.5.5"
+    "typescript": "^4.5.5",
+    "cjs-module-lexer": "^1.2.3"
   },
   "dependencies": {
     "esbuild": "^0.19.4",

tools/@aws-cdk/lazify/test/export-star.test.ts

@@ -1,6 +1,7 @@
 import * as fs from 'fs-extra';
 import * as path from 'path';
 import { transformFileContents } from '../lib';
+import { parse } from 'cjs-module-lexer';
 
 // Write a .js file in this directory that will be imported by tests below
 beforeEach(async () => {
@@ -12,21 +13,47 @@ beforeEach(async () => {
 
 test('replace __exportStar with getters', () => {
   const fakeFile = path.join(__dirname, 'index.ts');
-  expect(transformFileContents(fakeFile, [
+
+  const transformed = transformFileContents(fakeFile, [
     '__exportStar(require("./some-module"), exports);'
-  ].join('\n'))).toMatchInlineSnapshot(`
-"Object.defineProperty(exports, "foo", { configurable: true, get: () => require("./some-module").foo });
-Object.defineProperty(exports, "bar", { configurable: true, get: () => require("./some-module").bar });
-"
-`);
+  ].join('\n'));
+
+  expect(parse(transformed).exports).toEqual([
+    'foo',
+    'bar',
+  ]);
+
+  const mod = evalModule(transformed);
+  expect(mod.foo()).toEqual('foo');
+  expect(mod.bar).toEqual(5);
 });
 
 test('replace re-export with getter', () => {
   const fakeFile = path.join(__dirname, 'index.ts');
-  expect(transformFileContents(fakeFile, [
+  const transformed = transformFileContents(fakeFile, [
     'exports.some_module = require("./some-module");',
-  ].join('\n'))).toMatchInlineSnapshot(`
-"Object.defineProperty(exports, "some_module", { configurable: true, get: () => require("./some-module") });
-"
-`);
-});
+  ].join('\n'));
+
+  expect(parse(transformed).exports).toEqual([
+    'some_module',
+  ]);
+
+  const mod = evalModule(transformed);
+  expect(mod.some_module.foo()).toEqual('foo');
+  expect(mod.some_module.bar).toEqual(5);
+});
+
+/**
+ * Fake NodeJS evaluation of a module
+ */
+function evalModule(x: string) {
+  const code = [
+    '(function() {',
+    'const exports = {};',
+    'const module = { exports };',
+    x,
+    'return exports;',
+    '})()',
+  ].join('\n');
+  return eval(code);
+}

yarn.lock

@@ -5468,7 +5468,7 @@ cidr-regex@^3.1.1:
   dependencies:
     ip-regex "^4.1.0"
 
-cjs-module-lexer@^1.0.0:
+cjs-module-lexer@^1.0.0, cjs-module-lexer@^1.2.3:
   version "1.2.3"
   resolved "https://registry.npmjs.org/cjs-module-lexer/-/cjs-module-lexer-1.2.3.tgz#6c370ab19f8a3394e318fe682686ec0ac684d107"
   integrity sha512-0TNiGstbQmCFwt4akjjBg5pLRTSyj/PkWQ1ZoO2zntmg9yLqSRxwEa4iCfQLGjqhiqBfOJa7W/E8wfGrTDmlZQ==