fix(detector): enable decorators-legacy plugin for babel parse

Third-party sources that ship raw `@decorator` syntax (fontkit, older
MobX / Nest builds) tripped the same silent-drop failure mode as #264:
babel.parse threw, `detect()` logged a warning, and the file's
dependency graph was dropped. Enable `decorators-legacy` in both the
walker's detector and the ESM-transformer parse calls so these sources
parse cleanly and their requires/imports get bundled. Extend test-94
with a decorator fixture walked via `pkg.scripts`.

Author: robertsLando

eslint.config.js

@@ -15,6 +15,8 @@ module.exports = [
       'test/test-51-esm-import-meta/esm-module/test-import-meta-basic.js',
       'lib/log.js', // ESM re-export file
       'test/test-50-extensions/test-y-esnext.js', // ESM test file
+      'test/test-94-sea-esm-import-meta/app/lib/decorated.js', // decorator syntax fixture
+
       'prelude/sea-bootstrap.bundle.js', // Generated by esbuild
       'prelude/sea-bootstrap-esm.bundle.mjs', // Generated by esbuild
     ],

lib/detector.ts

@@ -549,12 +549,18 @@ function traverse(ast: babelTypes.File, visitor: VisitorFunction) {
   }
 }
 
-/** `babel.parse` wrapper. `isEsm` selects `sourceType: 'module'` so `import.meta` / top-level await parse cleanly. */
+/**
+ * `babel.parse` wrapper. `isEsm` selects `sourceType: 'module'` so `import.meta`
+ * / top-level await parse cleanly. `decorators-legacy` is enabled so third-party
+ * sources that ship raw `@decorator` syntax (fontkit, older MobX/Nest builds,
+ * etc.) don't trip the parser and silently drop their dependency graph.
+ */
 export function parse(body: string, isEsm = false) {
   return babel.parse(body, {
     allowImportExportEverywhere: true,
     allowReturnOutsideFunction: true,
     sourceType: isEsm ? 'module' : 'script',
+    plugins: ['decorators-legacy'],
   });
 }
 

lib/esm-transformer.ts

@@ -35,7 +35,7 @@ function hasImportMeta(code: string): boolean {
   try {
     const ast = babel.parse(code, {
       sourceType: 'module',
-      plugins: [],
+      plugins: ['decorators-legacy'],
     });
 
     if (!ast) {
@@ -85,7 +85,7 @@ function detectESMFeatures(
   try {
     const ast = babel.parse(code, {
       sourceType: 'module',
-      plugins: [],
+      plugins: ['decorators-legacy'],
     });
 
     if (!ast) {
@@ -300,7 +300,7 @@ export function transformESMtoCJS(
       // Parse the code to check for exports and collect imports
       const ast = babel.parse(code, {
         sourceType: 'module',
-        plugins: [],
+        plugins: ['decorators-legacy'],
       });
 
       let hasExports = false;

test/test-94-sea-esm-import-meta/app/lib/decorated.js

@@ -0,0 +1,16 @@
+// Decorator syntax forces the walker's Babel parser to enable the
+// `decorators-legacy` plugin. Without it pkg would log "Babel parse has
+// failed: This experimental syntax requires enabling one of the following
+// parser plugin(s)" and silently drop this file's dependency graph. This
+// file is walked via `pkg.scripts` but never imported at runtime — Node
+// can't execute raw decorator syntax.
+function log(Cls) {
+  return Cls;
+}
+
+@log
+export class Widget {
+  greet(name) {
+    return 'widget:' + name;
+  }
+}

test/test-94-sea-esm-import-meta/app/package.json

@@ -3,5 +3,10 @@
   "version": "1.0.0",
   "type": "module",
   "main": "index.mjs",
-  "bin": "index.mjs"
+  "bin": "index.mjs",
+  "pkg": {
+    "scripts": [
+      "lib/decorated.js"
+    ]
+  }
 }