Don't follow links when copying paths

The original intent of this method was to copy links as links, not to
deeply copy the content of linked directories. This was never tested and
the original implementation did not have this behavior.

Change behavior in place without a major version change since the new
behavior is what was intended. Add a test that both the sync and async
implementation copies links as links.

pkgs/io/CHANGELOG.md

@@ -1,3 +1,8 @@
+## 1.1.0
+
+* Copy links as links instead of deeply copying the content for all links in
+  `copyPath` and `copyPathSync`.
+
 ## 1.0.5
 
 * Require Dart 3.4.

pkgs/io/lib/src/copy_path.dart

@@ -30,7 +30,8 @@ Future<void> copyPath(String from, String to) async {
     return;
   }
   await Directory(to).create(recursive: true);
-  await for (final file in Directory(from).list(recursive: true)) {
+  await for (final file
+      in Directory(from).list(recursive: true, followLinks: false)) {
     final copyTo = p.join(to, p.relative(file.path, from: from));
     if (file is Directory) {
       await Directory(copyTo).create(recursive: true);
@@ -56,7 +57,8 @@ void copyPathSync(String from, String to) {
     return;
   }
   Directory(to).createSync(recursive: true);
-  for (final file in Directory(from).listSync(recursive: true)) {
+  for (final file
+      in Directory(from).listSync(recursive: true, followLinks: false)) {
     final copyTo = p.join(to, p.relative(file.path, from: from));
     if (file is Directory) {
       Directory(copyTo).createSync(recursive: true);

pkgs/io/pubspec.yaml

@@ -2,7 +2,7 @@ name: io
 description: >-
   Utilities for the Dart VM Runtime including support for ANSI colors, file
   copying, and standard exit code values.
-version: 1.0.5
+version: 1.1.0-wip
 repository: https://github.com/dart-lang/tools/tree/main/pkgs/io
 
 environment:

pkgs/io/test/copy_path_test.dart

@@ -5,6 +5,8 @@
 @TestOn('vm')
 library;
 
+import 'dart:io';
+
 import 'package:io/io.dart';
 import 'package:path/path.dart' as p;
 import 'package:test/test.dart';
@@ -33,6 +35,36 @@ void main() {
       throwsArgumentError,
     );
   });
+
+  test('links are preserved in async copy', () async {
+    await _create();
+    const linkTarget = 'link_target';
+    final targetPath = p.join(d.sandbox, linkTarget);
+    const linkSource = 'link_source';
+    await d.dir(linkTarget).create();
+    await Link(p.join(d.sandbox, _parentDir, linkSource)).create(targetPath);
+
+    await copyPath(p.join(d.sandbox, _parentDir), p.join(d.sandbox, _copyDir));
+
+    final expectedLink = Link(p.join(d.sandbox, _copyDir, linkSource));
+    expect(await expectedLink.exists(), isTrue);
+    expect(await expectedLink.target(), targetPath);
+  });
+
+  test('links are preserved in sync copy', () async {
+    await _create();
+    const linkTarget = 'link_target';
+    final targetPath = p.join(d.sandbox, linkTarget);
+    const linkSource = 'link_source';
+    await d.dir(linkTarget).create();
+    await Link(p.join(d.sandbox, _parentDir, linkSource)).create(targetPath);
+
+    copyPathSync(p.join(d.sandbox, _parentDir), p.join(d.sandbox, _copyDir));
+
+    final expectedLink = Link(p.join(d.sandbox, _copyDir, linkSource));
+    expect(await expectedLink.exists(), isTrue);
+    expect(await expectedLink.target(), targetPath);
+  });
 }
 
 const _parentDir = 'parent';