added findPackageConfigFilePath to find the package_config.json file

Author: jyameo

dwds/lib/src/loaders/strategy.dart

@@ -2,6 +2,7 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+import 'dart:io';
 import 'dart:typed_data';
 
 import 'package:dwds/src/debugging/dart_runtime_debugger.dart';
@@ -20,7 +21,7 @@ abstract class LoadStrategy {
   LoadStrategy(
     this._assetReader, {
     String? packageConfigPath,
-  }) : _packageConfigPath = packageConfigPath;
+  }) : _packageConfigPath = packageConfigPath ?? _findPackageConfigFilePath();
 
   /// The ID for this strategy.
   ///
@@ -83,6 +84,30 @@ abstract class LoadStrategy {
         'package_config.json',
       );
 
+  /// Returns the absolute file path of the `package_config.json` file in the `.dart_tool`
+  /// directory, searching recursively from the current directory hierarchy.
+  /// If `_packageConfigPath` is already set, it returns the cached value immediately.
+  static String? _findPackageConfigFilePath() {
+    var candidateDir = Directory(DartUri.currentDirectory).absolute;
+
+    while (true) {
+      final candidatePackageConfigFile =
+          File(p.join(candidateDir.path, '.dart_tool', 'package_config.json'));
+
+      if (candidatePackageConfigFile.existsSync()) {
+        return candidatePackageConfigFile.path;
+      }
+
+      final parentDir = candidateDir.parent;
+      if (parentDir.path == candidateDir.path) {
+        // We've reached the root directory
+        return null;
+      }
+
+      candidateDir = parentDir;
+    }
+  }
+
   /// Returns the bootstrap required for this [LoadStrategy].
   ///
   /// The bootstrap is appended to the end of the entry point module.