fix: make sourcemap renames scope aware (#1827)

Uses Acorn to parse compiled files and create a tree of scopes. Then,
only apply renames in scopes when appropriate. This is far better than
what we were doing before when we were just looking for nearby renames.

This is not very fast for large bundled files. I initially worked on
building a fork of https://github.com/guybedford/es-module-lexer that
would scan for blocks. This worked in many cases, but failed for cases
when there's no BlockStatement. For example, `for (const foo of bar) foo()`
would not detect a 'scope' around `foo()`. This is not great, especially
with minified code where such patterns are common.

Instead, we'll parse large bundles (>512KB) in a one-off worker_thread.
We also some work in our build process to vendor acorn and acorn-loose
to avoid duplicating it in the worker thread code.

Author: connor4312

CHANGELOG.md

@@ -4,6 +4,7 @@ This changelog records changes to stable releases since 1.50.2. "TBA" changes he
 
 ## Nightly (only)
 
+- fix: make source map renames scope-aware
 - fix: error when processing private properties with a map ([#1824](https://github.com/microsoft/vscode-js-debug/issues/1824))
 
 ## v1.83 (September 2023)

gulpfile.js

@@ -192,17 +192,54 @@ async function getConstantDefines() {
   };
 }
 
+function compileVendorLibrary(name) {
+  return {
+    name,
+    entryPoints: [require.resolve(name)],
+    outdir: `${buildSrcDir}/vendor`,
+    entryNames: `${name}`,
+  };
+}
+
 async function compileTs({
   packages = [],
   sourcemap = false,
   compileInPlace = false,
   minify = isWatch ? false : true,
   watch = false,
 } = options) {
+  const vendorPrefix = 'vendor';
+
+  // don't watch these, they won't really change:
+  const vendors = new Map(
+    await Promise.all(
+      [
+        {
+          ...compileVendorLibrary('acorn-loose'),
+          plugins: [esbuildPlugins.hackyVendorBundle(new Map([['acorn', './acorn']]))],
+        },
+        compileVendorLibrary('acorn'),
+      ].map(async ({ name, ...opts }) => {
+        await esbuild.build({
+          ...opts,
+          sourcemap,
+          bundle: true,
+          platform: 'node',
+          format: 'cjs',
+          target: 'node18',
+          minify,
+        });
+
+        return [name, `./${vendorPrefix}/${name}.js`];
+      }),
+    ),
+  );
+
   // add the entrypoints common to both vscode and vs here
   packages = [
     ...packages,
     { entry: `${srcDir}/common/hash/hash.ts`, library: false },
+    { entry: `${srcDir}/common/sourceMaps/renameWorker.ts`, library: false },
     { entry: `${srcDir}/targets/node/bootloader.ts`, library: false, target: 'node10' },
     { entry: `${srcDir}/targets/node/watchdog.ts`, library: false, target: 'node10' },
     {
@@ -222,7 +259,7 @@ async function compileTs({
     library,
     isInVsCode,
     nodePackages,
-    target = 'node16',
+    target = 'node18',
   } of packages) {
     todo.push(
       incrementalEsbuild({
@@ -245,6 +282,7 @@ async function compileTs({
           esbuildPlugins.nativeNodeModulesPlugin(),
           esbuildPlugins.importGlobLazy(),
           esbuildPlugins.dirname(/src.test./),
+          esbuildPlugins.hackyVendorBundle(vendors),
         ],
         format: library ? 'cjs' : 'iife',
       }),