lib: improve error message when index not found on cjs

PR-URL: #53859
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Marco Ippolito <marcoippolito54@gmail.com>

src/node_file.cc

@@ -3143,6 +3143,8 @@ void BindingData::LegacyMainResolve(const FunctionCallbackInfo<Value>& args) {
     return;
   }
 
+  std::string package_initial_file = "";
+
   ada::result<ada::url_aggregator> file_path_url;
   std::optional<std::string> initial_file_path;
   std::string file_path;
@@ -3165,6 +3167,8 @@ void BindingData::LegacyMainResolve(const FunctionCallbackInfo<Value>& args) {
 
     node::url::FromNamespacedPath(&initial_file_path.value());
 
+    package_initial_file = *initial_file_path;
+
     for (int i = 0; i < legacy_main_extensions_with_main_end; i++) {
       file_path = *initial_file_path + std::string(legacy_main_extensions[i]);
 
@@ -3220,13 +3224,10 @@ void BindingData::LegacyMainResolve(const FunctionCallbackInfo<Value>& args) {
     }
   }
 
-  std::optional<std::string> module_path =
-      node::url::FileURLToPath(env, *package_json_url);
-  std::optional<std::string> module_base;
+  if (package_initial_file == "")
+    package_initial_file = *initial_file_path + ".js";
 
-  if (!module_path.has_value()) {
-    return;
-  }
+  std::optional<std::string> module_base;
 
   if (args.Length() >= 3 && args[2]->IsString()) {
     Utf8Value utf8_base_path(isolate, args[2]);
@@ -3251,7 +3252,7 @@ void BindingData::LegacyMainResolve(const FunctionCallbackInfo<Value>& args) {
 
   THROW_ERR_MODULE_NOT_FOUND(isolate,
                              "Cannot find package '%s' imported from %s",
-                             *module_path,
+                             package_initial_file,
                              *module_base);
 }
 

test/es-module/test-cjs-legacyMainResolve.js

@@ -129,15 +129,28 @@ describe('legacyMainResolve', () => {
     );
     assert.throws(
       () => legacyMainResolve(packageJsonUrl, { main: null }, packageJsonUrl),
-      { code: 'ERR_MODULE_NOT_FOUND' },
+      { message: /index\.js/, code: 'ERR_MODULE_NOT_FOUND' },
     );
   });
 
   it('should not crash when cannot resolve to a file that contains special chars', () => {
     const packageJsonUrl = pathToFileURL('/c/file%20with%20percents/package.json');
     assert.throws(
       () => legacyMainResolve(packageJsonUrl, { main: null }, packageJsonUrl),
-      { code: 'ERR_MODULE_NOT_FOUND' },
+      { message: /index\.js/, code: 'ERR_MODULE_NOT_FOUND' },
+    );
+  });
+
+  it('should report main file on error message when not found', () => {
+    const packageJsonUrl = pathToFileURL(
+      path.resolve(
+        fixtures.path('/es-modules/legacy-main-resolver'),
+        'package.json'
+      )
+    );
+    assert.throws(
+      () => legacyMainResolve(packageJsonUrl, { main: './index.node' }, packageJsonUrl),
+      { message: /index\.node/, code: 'ERR_MODULE_NOT_FOUND' },
     );
   });