add a test that the arg parser library only depends on package:args (#213)

cc @alexmarkov

Author: jakemac53

pkgs/dart_mcp_server/pubspec.yaml

@@ -40,7 +40,9 @@ dependencies:
   yaml: ^3.1.3
 
 dev_dependencies:
+  analyzer: ^7.5.2
   dart_flutter_team_lints: ^3.2.1
+  pub_semver: ^2.2.0
   test: ^1.25.15
   test_descriptor: ^2.0.2
   test_process: ^2.1.1

pkgs/dart_mcp_server/test/arg_parser_test.dart

@@ -0,0 +1,48 @@
+// Copyright (c) 2025, the Dart project authors.  Please see the AUTHORS file
+// 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.
+
+@TestOn('!windows')
+library;
+
+import 'dart:isolate';
+
+import 'package:analyzer/dart/analysis/features.dart';
+import 'package:analyzer/dart/analysis/utilities.dart';
+import 'package:analyzer/dart/ast/ast.dart';
+import 'package:pub_semver/pub_semver.dart';
+import 'package:test/test.dart';
+
+void main() {
+  test('public arg parser library only exports lib/src/arg_parser.dart', () {
+    checkDependencies('package:dart_mcp_server/arg_parser.dart', const [
+      'src/arg_parser.dart',
+    ]);
+  });
+
+  test('arg parser implementation only depends on package:args', () {
+    checkDependencies('package:dart_mcp_server/src/arg_parser.dart', const [
+      'package:args/args.dart',
+    ]);
+  });
+}
+
+/// Checks that [libraryUri] only has directives referencing [allowedUris].
+///
+/// The [allowedUris] are matched based on the exact string, not a resolved
+/// URI.
+void checkDependencies(String libraryUri, Iterable<String> allowedUris) {
+  final parsed = parseFile(
+    path: Isolate.resolvePackageUriSync(Uri.parse(libraryUri))!.path,
+    featureSet: FeatureSet.fromEnableFlags2(
+      sdkLanguageVersion: Version.parse('3.9.0'),
+      flags: const [],
+    ),
+  );
+  final uriDirectives = parsed.unit.directives.whereType<UriBasedDirective>();
+
+  expect(
+    uriDirectives.map((d) => d.uri.stringValue),
+    unorderedEquals(allowedUris),
+  );
+}