Refactor fake

pkgs/io_file/lib/io_file.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.
 
+export 'src/exceptions.dart';
 export 'src/file_system.dart';
 export 'src/vm_file_system_property.dart'
     if (dart.library.html) 'src/web_file_system_property.dart';

pkgs/io_file/lib/posix_file_system.dart

@@ -2,5 +2,4 @@
 // 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.
 
-export 'src/vm_posix_file_system.dart'
-    if (dart.library.html) 'src/web_posix_file_system.dart';
+export 'src/posix_file_system.dart';

pkgs/io_file/lib/src/exceptions.dart

@@ -0,0 +1,66 @@
+// 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.
+
+class SystemCallError {
+  final String systemCall;
+  final int errorCode;
+  final String message;
+
+  const SystemCallError(this.systemCall, this.errorCode, this.message);
+}
+
+class IOFileException implements Exception {
+  final String message;
+
+  /// The file system path on which the error occurred.
+  ///
+  /// Can be `null` if the exception does not relate directly
+  /// to a file system path.
+  final String? path;
+
+  /// The underlying OS error.
+  ///
+  /// Can be `null` if the exception is not raised due to an OS error.
+  final SystemCallError? systemCall;
+
+  const IOFileException(this.message, {this.path, this.systemCall});
+
+  String _toStringHelper(String className) {
+    final sb = StringBuffer('$className: $message');
+    if (path != null) {
+      sb.write(', path = "$path"');
+    }
+    if (systemCall != null) {
+      sb.write(
+        ' (${systemCall!.systemCall}: ${systemCall!.message}, '
+        'errno=${systemCall!.errorCode} )',
+      );
+    }
+    return sb.toString();
+  }
+
+  @override
+  String toString() => _toStringHelper('IOFileException');
+}
+
+class PathAccessException extends IOFileException {
+  const PathAccessException(super.message, {super.path, super.systemCall});
+
+  @override
+  String toString() => _toStringHelper('PathAccessException');
+}
+
+class PathExistsException extends IOFileException {
+  const PathExistsException(super.message, {super.path, super.systemCall});
+
+  @override
+  String toString() => _toStringHelper('PathExistsException');
+}
+
+class PathNotFoundException extends IOFileException {
+  const PathNotFoundException(super.message, {super.path, super.systemCall});
+
+  @override
+  String toString() => _toStringHelper('PathNotFoundException');
+}

pkgs/io_file/lib/src/fake_posix_file_system.dart

@@ -0,0 +1,211 @@
+import 'dart:convert';
+
+import 'dart:typed_data';
+
+import 'package:path/path.dart' as p;
+
+import 'exceptions.dart';
+import 'file_system.dart';
+import 'posix_file_system.dart';
+
+sealed class _Entity {}
+
+class _File extends _Entity {
+  _File();
+}
+
+class _Directory extends _Entity {
+  final children = <String, _Entity>{};
+
+  @override
+  String toString() => '<Directory children=$children>';
+}
+
+class _FakeMetadata implements PosixMetadata {
+  @override
+  DateTime get access => throw UnimplementedError();
+
+  @override
+  DateTime? get creation => throw UnimplementedError();
+
+  @override
+  bool get isDirectory => this.type == FileSystemType.directory;
+
+  @override
+  bool get isFile => throw UnimplementedError();
+
+  @override
+  bool? get isHidden => throw UnimplementedError();
+
+  @override
+  bool get isLink => throw UnimplementedError();
+
+  @override
+  DateTime get modification => throw UnimplementedError();
+
+  @override
+  int get size => throw UnimplementedError();
+
+  @override
+  final FileSystemType type;
+
+  _FakeMetadata(this.type);
+
+  @override
+  int get accessedTimeNanos => throw UnimplementedError();
+
+  @override
+  int? get creationTimeNanos => throw UnimplementedError();
+
+  @override
+  int get modificationTimeNanos => throw UnimplementedError();
+}
+
+final class FakePosixFileSystem extends PosixFileSystem {
+  final context = p.Context(style: p.Style.posix);
+  final root = _Directory();
+  final tmp = _Directory();
+
+  FakePosixFileSystem() {
+    print('Reset!');
+    root.children['tmp'] = tmp;
+  }
+
+  _Entity? _findComponents(List<String> components) {
+    _Entity e = root;
+    for (var child in components.skip(1)) {
+      print('$child => $e');
+      if (e is _Directory) {
+        if (!e.children.containsKey(child)) return null;
+        e = e.children[child]!;
+      } else {
+        return null;
+      }
+    }
+    return e;
+  }
+
+  _Entity? _findEntity(String path) {
+    path = context.absolute(path);
+    return _findComponents(p.split(path));
+  }
+
+  _Entity? _upToLast(String path) {
+    path = context.absolute(path);
+    return _findComponents(p.split(p.dirname(path)));
+  }
+
+  @override
+  void createDirectory(String path) {
+    print('createDirectory($path)');
+    if (_findEntity(path) != null) {
+      throw PathExistsException(
+        'create directory failed',
+        path: path,
+        systemCall: const SystemCallError('XXX', 17, 'XXX'),
+      );
+    }
+    path = context.absolute(path);
+    final base = context.basename(path);
+
+    final parent = _upToLast(path);
+    print('parent $parent');
+    if (parent is _Directory) {
+      parent.children[base] = _Directory();
+    } else if (parent == null) {
+      throw PathNotFoundException(
+        'create directory failed',
+        path: path,
+        systemCall: const SystemCallError('XXX', 2, 'XXX'),
+      );
+    } else {
+      throw UnsupportedError(path);
+    }
+  }
+
+  @override
+  String createTemporaryDirectory({String? parent, String? prefix}) {
+    final parentDir = parent ?? '/tmp';
+
+    String path = p.join(parentDir, prefix);
+    createDirectory(path);
+    return path;
+  }
+
+  @override
+  Metadata metadata(String path) {
+    final e = _findEntity(path);
+    return _FakeMetadata(switch (e) {
+      _Directory() => FileSystemType.directory,
+      _File() => FileSystemType.file,
+      _ => FileSystemType.unknown,
+    });
+  }
+
+  @override
+  Uint8List readAsBytes(String path) {
+    // TODO: implement readAsBytes
+    throw UnimplementedError();
+  }
+
+  @override
+  void removeDirectory(String path) {
+    // TODO: implement removeDirectory
+  }
+
+  @override
+  void removeDirectoryTree(String path) {
+    final parent = _upToLast(path);
+    final base = context.basename(path);
+
+    if (parent is _Directory) {
+      if (parent.children.containsKey(base)) {
+        // Check that it is a directory.
+        parent.children.remove(base);
+      } else {
+        throw UnsupportedError('XXX');
+      }
+    } else {
+      throw UnsupportedError('XXX');
+    }
+  }
+
+  @override
+  void rename(String oldPath, String newPath) {
+    // TODO: implement rename
+  }
+
+  @override
+  bool same(String path1, String path2) {
+    // TODO: implement same
+    throw UnimplementedError();
+  }
+
+  @override
+  void writeAsBytes(
+    String path,
+    Uint8List data, [
+    WriteMode mode = WriteMode.failExisting,
+  ]) {
+    // TODO: implement writeAsBytes
+  }
+
+  @override
+  void writeAsString(
+    String path,
+    String contents, [
+    WriteMode mode = WriteMode.failExisting,
+    Encoding encoding = utf8,
+    String? lineTerminator,
+  ]) {
+    final parent = _upToLast(path);
+    final base = context.basename(path);
+
+    if (parent is _Directory) {
+      // Do something with the file contents.
+      parent.children[base] = _File();
+    } else {
+      throw UnsupportedError('XXX');
+    }
+  }
+}

pkgs/io_file/lib/src/file_system.dart

@@ -132,7 +132,7 @@ class WriteMode {
 ///
 /// TODO(brianquinlan): Far now, this class is not meant to be implemented,
 /// extended outside of this package. Clarify somewhere that people implementing
-/// this class should reach out to be.
+/// this class should reach out to me.
 @sealed
 abstract class FileSystem {
   /// Create a directory at the given path.

pkgs/io_file/lib/src/vm_posix_file_system.dart → pkgs/io_file/lib/src/native_posix_file_system.dart

@@ -11,9 +11,11 @@ import 'dart:typed_data';
 import 'package:ffi/ffi.dart' as ffi;
 import 'package:path/path.dart' as p;
 
+import 'exceptions.dart';
 import 'file_system.dart';
 import 'internal_constants.dart';
 import 'libc.dart' as libc;
+import 'posix_file_system.dart';
 
 /// The default `mode` to use with `open` calls that may create a file.
 const _defaultMode = 438; // => 0666 => rw-rw-rw-
@@ -26,23 +28,24 @@ const _nanosecondsPerSecond = 1000000000;
 bool _isDotOrDotDot(Pointer<Char> s) => // ord('.') == 46
     s[0] == 46 && ((s[1] == 0) || (s[1] == 46 && s[2] == 0));
 
-Exception _getError(int err, String message, String path) {
+Exception _getError(int err, String message, String path, String systemCall) {
   // TODO(brianquinlan): In the long-term, do we need to avoid exceptions that
   // are part of `dart:io`? Can we move those exceptions into a different
   // namespace?
-  final osError = io.OSError(
-    libc.strerror(err).cast<ffi.Utf8>().toDartString(),
+  final systemError = SystemCallError(
+    systemCall,
     err,
+    libc.strerror(err).cast<ffi.Utf8>().toDartString(),
   );
 
   if (err == libc.EPERM || err == libc.EACCES) {
-    return io.PathAccessException(path, osError, message);
+    return PathAccessException(message, path: path, systemCall: systemError);
   } else if (err == libc.EEXIST) {
-    return io.PathExistsException(path, osError, message);
+    return PathExistsException(message, path: path, systemCall: systemError);
   } else if (err == libc.ENOENT) {
-    return io.PathNotFoundException(path, osError, message);
+    return PathNotFoundException(message, path: path, systemCall: systemError);
   } else {
-    return io.FileSystemException(message, path, osError);
+    return IOFileException(message, path: path, systemCall: systemError);
   }
 }
 
@@ -56,7 +59,7 @@ int _tempFailureRetry(int Function() f) {
 }
 
 /// Information about a directory, link, etc. stored in the [PosixFileSystem].
-final class PosixMetadata implements Metadata {
+final class NativePosixMetadata implements PosixMetadata {
   /// The `st_mode` field of the POSIX stat struct.
   ///
   /// See [stat.h](https://pubs.opengroup.org/onlinepubs/009696799/basedefs/sys/stat.h.html)
@@ -67,27 +70,13 @@ final class PosixMetadata implements Metadata {
   @override
   final int size;
 
-  /// The time that the file system object was last accessed in nanoseconds
-  /// since the epoch.
-  ///
-  /// Access time is updated when the object is read or modified.
-  ///
-  /// The resolution of the access time varies by platform and file system.
+  @override
   final int accessedTimeNanos;
 
-  /// The time that the file system object was created in nanoseconds since the
-  /// epoch.
-  ///
-  /// This will always be `null` on Android and Linux.
-  ///
-  /// The resolution of the creation time varies by platform and file system.
+  @override
   final int? creationTimeNanos;
 
-  /// The time that the file system object was last modified in nanoseconds
-  /// since the epoch.
-  ///
-  /// The resolution of the modification time varies by platform and file
-  /// system.
+  @override
   final int modificationTimeNanos;
 
   int get _fmt => mode & libc.S_IFMT;
@@ -149,7 +138,7 @@ final class PosixMetadata implements Metadata {
     return null;
   }
 
-  PosixMetadata._(
+  NativePosixMetadata._(
     this.mode,
     this._flags,
     this.size,
@@ -158,15 +147,15 @@ final class PosixMetadata implements Metadata {
     this.modificationTimeNanos,
   );
 
-  /// Construct [PosixMetadata] from data returned by the `stat` system call.
-  factory PosixMetadata.fromFileAttributes({
+  /// Construct [NativePosixMetadata] from data returned by the `stat` system call.
+  factory NativePosixMetadata.fromFileAttributes({
     required int mode,
     int flags = 0,
     int size = 0,
     int accessedTimeNanos = 0,
     int? creationTimeNanos,
     int modificationTimeNanos = 0,
-  }) => PosixMetadata._(
+  }) => NativePosixMetadata._(
     mode,
     flags,
     size,
@@ -177,7 +166,7 @@ final class PosixMetadata implements Metadata {
 
   @override
   bool operator ==(Object other) =>
-      other is PosixMetadata &&
+      other is NativePosixMetadata &&
       mode == other.mode &&
       _flags == other._flags &&
       size == other.size &&
@@ -210,19 +199,19 @@ external int write(int fd, Pointer<Uint8> buf, int count);
 
 /// A [FileSystem] implementation for POSIX systems (e.g. Android, iOS, Linux,
 /// macOS).
-final class PosixFileSystem extends FileSystem {
+final class NativePosixFileSystem extends PosixFileSystem {
   @override
   bool same(String path1, String path2) => ffi.using((arena) {
     final stat1 = arena<libc.Stat>();
     if (libc.stat(path1.toNativeUtf8(allocator: arena).cast(), stat1) == -1) {
       final errno = libc.errno;
-      throw _getError(errno, 'stat failed', path1);
+      throw _getError(errno, 'stat failed', path1, 'stat');
     }
 
     final stat2 = arena<libc.Stat>();
     if (libc.stat(path2.toNativeUtf8(allocator: arena).cast(), stat2) == -1) {
       final errno = libc.errno;
-      throw _getError(errno, 'stat failed', path2);
+      throw _getError(errno, 'stat failed', path2, 'stat');
     }
 
     return (stat1.ref.st_ino == stat2.ref.st_ino) &&
@@ -237,7 +226,7 @@ final class PosixFileSystem extends FileSystem {
         ) ==
         -1) {
       final errno = libc.errno;
-      throw _getError(errno, 'create directory failed', path);
+      throw _getError(errno, 'create directory failed', path, 'mkdir');
     }
   });
 
@@ -252,21 +241,21 @@ final class PosixFileSystem extends FileSystem {
         );
         if (path == nullptr) {
           final errno = libc.errno;
-          throw _getError(errno, 'mkdtemp failed', template);
+          throw _getError(errno, 'mkdtemp failed', template, 'mkdtemp');
         }
         return path.cast<ffi.Utf8>().toDartString();
       });
 
   @override
-  PosixMetadata metadata(String path) => ffi.using((arena) {
+  NativePosixMetadata metadata(String path) => ffi.using((arena) {
     final stat = arena<libc.Stat>();
 
     if (libc.lstat(path.toNativeUtf8(allocator: arena).cast(), stat) == -1) {
       final errno = libc.errno;
-      throw _getError(errno, 'stat failed', path);
+      throw _getError(errno, 'stat failed', path, 'lstat');
     }
 
-    return PosixMetadata.fromFileAttributes(
+    return NativePosixMetadata.fromFileAttributes(
       mode: stat.ref.st_mode,
       flags: stat.ref.st_flags,
       size: stat.ref.st_size,
@@ -291,7 +280,7 @@ final class PosixFileSystem extends FileSystem {
         ) ==
         -1) {
       final errno = libc.errno;
-      throw _getError(errno, 'remove directory failed', path);
+      throw _getError(errno, 'remove directory failed', path, 'unlinkat');
     }
   });
 
@@ -308,13 +297,13 @@ final class PosixFileSystem extends FileSystem {
     );
     if (fd == -1) {
       final errno = libc.errno;
-      throw _getError(errno, 'openat failed', path);
+      throw _getError(errno, 'openat failed', path, 'openat');
     }
     try {
       final dir = libc.fdopendir(fd);
       if (dir == nullptr) {
         final errno = libc.errno;
-        throw _getError(errno, 'fdopendir failed', path);
+        throw _getError(errno, 'fdopendir failed', path, 'fdopendir');
       }
       try {
         // `readdir` returns `NULL` but leaves `errno` unchanged if the end of
@@ -344,7 +333,7 @@ final class PosixFileSystem extends FileSystem {
             /// DT_UNKNOWN.
             if (libc.fstatat(fd, child, stat, libc.AT_SYMLINK_NOFOLLOW) == -1) {
               final errno = libc.errno;
-              throw _getError(errno, 'fstatat failed', childPath);
+              throw _getError(errno, 'fstatat failed', childPath, 'fstatat');
             }
             type =
                 stat.ref.st_mode & libc.S_IFMT == libc.S_IFDIR
@@ -356,19 +345,19 @@ final class PosixFileSystem extends FileSystem {
           } else {
             if (libc.unlinkat(fd, child, 0) == -1) {
               final errno = libc.errno;
-              throw _getError(errno, 'unlinkat failed', childPath);
+              throw _getError(errno, 'unlinkat failed', childPath, 'unlinkat');
             }
           }
           libc.errno = 0;
           dirent = libc.readdir(dir);
         }
         if (libc.errno != 0) {
           final errno = libc.errno;
-          throw _getError(errno, 'readdir failed', path);
+          throw _getError(errno, 'readdir failed', path, 'readdir');
         }
         if (libc.unlinkat(parentfd, name.cast(), libc.AT_REMOVEDIR) == -1) {
           final errno = libc.errno;
-          throw _getError(errno, 'unlinkat failed', path);
+          throw _getError(errno, 'unlinkat failed', path, 'unlinkat');
         }
       } finally {
         libc.closedir(dir);
@@ -396,7 +385,7 @@ final class PosixFileSystem extends FileSystem {
         ) !=
         0) {
       final errno = libc.errno;
-      throw _getError(errno, 'rename failed', oldPath);
+      throw _getError(errno, 'rename failed', oldPath, 'rename');
     }
   });
 
@@ -411,7 +400,7 @@ final class PosixFileSystem extends FileSystem {
     );
     if (fd == -1) {
       final errno = libc.errno;
-      throw _getError(errno, 'open failed', path);
+      throw _getError(errno, 'open failed', path, 'open');
     }
     try {
       final stat = arena<libc.Stat>();
@@ -439,7 +428,7 @@ final class PosixFileSystem extends FileSystem {
       switch (r) {
         case -1:
           final errno = libc.errno;
-          throw _getError(errno, 'read failed', path);
+          throw _getError(errno, 'read failed', path, 'read');
         case 0:
           return builder.takeBytes();
         default:
@@ -467,7 +456,7 @@ final class PosixFileSystem extends FileSystem {
         switch (r) {
           case -1:
             final errno = libc.errno;
-            throw _getError(errno, 'read failed', path);
+            throw _getError(errno, 'read failed', path, 'read');
           case 0:
             return buffer.asTypedList(
               bufferOffset,
@@ -524,7 +513,7 @@ final class PosixFileSystem extends FileSystem {
     try {
       if (fd == -1) {
         final errno = libc.errno;
-        throw _getError(errno, 'open failed', path);
+        throw _getError(errno, 'open failed', path, 'open');
       }
 
       ffi.using((arena) {
@@ -541,7 +530,7 @@ final class PosixFileSystem extends FileSystem {
           );
           if (w == -1) {
             final errno = libc.errno;
-            throw _getError(errno, 'write failed', path);
+            throw _getError(errno, 'write failed', path, 'write');
           }
           remaining -= w;
           buffer += w;

pkgs/io_file/lib/src/posix_file_system.dart

@@ -0,0 +1,22 @@
+import '../io_file.dart';
+
+abstract class PosixMetadata implements Metadata {
+  int get accessedTimeNanos;
+
+  /// The time that the file system object was created in nanoseconds since the
+  /// epoch.
+  ///
+  /// This will always be `null` on Android and Linux.
+  ///
+  /// The resolution of the creation time varies by platform and file system.
+  int? get creationTimeNanos;
+
+  /// The time that the file system object was last modified in nanoseconds
+  /// since the epoch.
+  ///
+  /// The resolution of the modification time varies by platform and file
+  /// system.
+  int get modificationTimeNanos;
+}
+
+abstract class PosixFileSystem extends FileSystem {}

pkgs/io_file/lib/src/vm_file_system_property.dart

@@ -5,9 +5,9 @@
 import 'dart:io';
 
 import 'file_system.dart';
-import 'vm_posix_file_system.dart';
+import 'native_posix_file_system.dart';
 import 'vm_windows_file_system.dart';
 
 /// Return the default [FileSystem] for the current platform.
 FileSystem get fileSystem =>
-    Platform.isWindows ? WindowsFileSystem() : PosixFileSystem();
+    Platform.isWindows ? WindowsFileSystem() : NativePosixFileSystem();

pkgs/io_file/lib/src/vm_windows_file_system.dart

@@ -13,6 +13,7 @@ import 'package:ffi/ffi.dart' as ffi;
 import 'package:path/path.dart' as p;
 import 'package:win32/win32.dart' as win32;
 
+import 'exceptions.dart';
 import 'file_system.dart';
 import 'internal_constants.dart';
 
@@ -52,8 +53,19 @@ String _formatMessage(int errorCode) {
   }
 }
 
-Exception _getError(int errorCode, String message, [String? path]) {
-  final osError = io.OSError(_formatMessage(errorCode), errorCode);
+// FileSystemException: unable to delete directory (OS Error: no such file or directory, errno=2): /tmp/somedir
+// FileSystemException: unable to delete directory, path="/tmp/somedir" (unlinkat: 2, no such file or directory)
+Exception _getError(
+  String message,
+  int errorCode,
+  String systemCall, [
+  String? path,
+]) {
+  final systemError = SystemCallError(
+    systemCall,
+    errorCode,
+    _formatMessage(errorCode),
+  );
 
   if (path != null) {
     switch (errorCode) {
@@ -65,10 +77,18 @@ Exception _getError(int errorCode, String message, [String? path]) {
       case win32.ERROR_LOCK_VIOLATION:
       case win32.ERROR_NETWORK_ACCESS_DENIED:
       case win32.ERROR_DRIVE_LOCKED:
-        return io.PathAccessException(path, osError, message);
+        return PathAccessException(
+          message,
+          path: path,
+          systemCall: systemError,
+        );
       case win32.ERROR_FILE_EXISTS:
       case win32.ERROR_ALREADY_EXISTS:
-        return io.PathExistsException(path, osError, message);
+        return PathExistsException(
+          message,
+          path: path,
+          systemCall: systemError,
+        );
       case win32.ERROR_FILE_NOT_FOUND:
       case win32.ERROR_PATH_NOT_FOUND:
       case win32.ERROR_INVALID_DRIVE:
@@ -77,12 +97,16 @@ Exception _getError(int errorCode, String message, [String? path]) {
       case win32.ERROR_BAD_NETPATH:
       case win32.ERROR_BAD_NET_NAME:
       case win32.ERROR_BAD_PATHNAME:
-        return io.PathNotFoundException(path, osError, message);
+        return PathNotFoundException(
+          message,
+          path: path,
+          systemCall: systemError,
+        );
       default:
-        return io.FileSystemException(message, path, osError);
+        return IOFileException(message, path: path, systemCall: systemError);
     }
   } else {
-    return io.FileSystemException(message, path, osError);
+    return IOFileException(message, path: path, systemCall: systemError);
   }
 }
 
@@ -257,7 +281,12 @@ final class WindowsFileSystem extends FileSystem {
     if (win32.CreateDirectory(path.toNativeUtf16(allocator: arena), nullptr) ==
         win32.FALSE) {
       final errorCode = win32.GetLastError();
-      throw _getError(errorCode, 'create directory failed', path);
+      throw _getError(
+        'create directory failed',
+        errorCode,
+        'CreateDirectory',
+        path,
+      );
     }
   });
 
@@ -279,7 +308,12 @@ final class WindowsFileSystem extends FileSystem {
     if (win32.RemoveDirectory(path.toNativeUtf16(allocator: arena)) ==
         win32.FALSE) {
       final errorCode = win32.GetLastError();
-      throw _getError(errorCode, 'remove directory failed', path);
+      throw _getError(
+        'remove directory failed',
+        errorCode,
+        'RemoveDirectory',
+        path,
+      );
     }
   });
 
@@ -297,7 +331,12 @@ final class WindowsFileSystem extends FileSystem {
 
     if (findHandle == win32.INVALID_HANDLE_VALUE) {
       final errorCode = win32.GetLastError();
-      throw _getError(errorCode, 'FindFirstFile failed', path);
+      throw _getError(
+        'removeDirectoryTree failed',
+        errorCode,
+        'FindFirstFile',
+        path,
+      );
     }
 
     do {
@@ -316,16 +355,22 @@ final class WindowsFileSystem extends FileSystem {
               win32.FALSE) {
             final errorCode = win32.GetLastError();
             throw _getError(
+              'removeDirectoryTree failed',
               errorCode,
-              'RemoveDirectory failed for link',
+              'RemoveDirectory',
               fullPath,
             );
           }
         } else {
           if (win32.DeleteFile(fullPath.toNativeUtf16(allocator: arena)) ==
               win32.FALSE) {
             final errorCode = win32.GetLastError();
-            throw _getError(errorCode, 'DeleteFile failed for link', fullPath);
+            throw _getError(
+              'removeDirectoryTree failed',
+              errorCode,
+              'DeleteFile',
+              fullPath,
+            );
           }
         }
       } else if ((attributes & win32.FILE_ATTRIBUTE_DIRECTORY) != 0) {
@@ -334,20 +379,35 @@ final class WindowsFileSystem extends FileSystem {
         if (win32.DeleteFile(fullPath.toNativeUtf16(allocator: arena)) ==
             win32.FALSE) {
           final errorCode = win32.GetLastError();
-          throw _getError(errorCode, 'DeleteFile failed', fullPath);
+          throw _getError(
+            'removeDirectoryTree failed',
+            errorCode,
+            'DeleteFile',
+            fullPath,
+          );
         }
       }
     } while (win32.FindNextFile(findHandle, findData) != win32.FALSE);
 
     final errorCode = win32.GetLastError();
     if (errorCode != win32.ERROR_NO_MORE_FILES) {
-      throw _getError(errorCode, 'FindNextFile failed', path);
+      throw _getError(
+        'removeDirectoryTree failed',
+        errorCode,
+        'FindNextFile',
+        path,
+      );
     }
 
     if (win32.RemoveDirectory(path.toNativeUtf16(allocator: arena)) ==
         win32.FALSE) {
       final errorCode = win32.GetLastError();
-      throw _getError(errorCode, 'remove directory failed', path);
+      throw _getError(
+        'removeDirectoryTree failed',
+        errorCode,
+        'RemoveDirectory',
+        path,
+      );
     }
   });
 
@@ -362,7 +422,7 @@ final class WindowsFileSystem extends FileSystem {
         ) ==
         win32.FALSE) {
       final errorCode = win32.GetLastError();
-      throw _getError(errorCode, 'rename failed', oldPath);
+      throw _getError('rename failed', errorCode, 'MoveFileEx', oldPath);
     }
   });
 
@@ -407,7 +467,12 @@ final class WindowsFileSystem extends FileSystem {
           ) ==
           win32.FALSE) {
         final errorCode = win32.GetLastError();
-        throw _getError(errorCode, 'set metadata failed', path);
+        throw _getError(
+          'set metadata failed',
+          errorCode,
+          'GetFileAttributesEx',
+          path,
+        );
       }
       attributes = fileInfo.ref.dwFileAttributes;
     } else {
@@ -456,7 +521,12 @@ final class WindowsFileSystem extends FileSystem {
     }
     if (win32.SetFileAttributes(nativePath, attributes) == win32.FALSE) {
       final errorCode = win32.GetLastError();
-      throw _getError(errorCode, 'set metadata failed', path);
+      throw _getError(
+        'set metadata failed',
+        errorCode,
+        'SetFileAttributes',
+        path,
+      );
     }
   });
 
@@ -473,7 +543,12 @@ final class WindowsFileSystem extends FileSystem {
         ) ==
         win32.FALSE) {
       final errorCode = win32.GetLastError();
-      throw _getError(errorCode, 'metadata failed', path);
+      throw _getError(
+        'metadata failed',
+        errorCode,
+        'GetFileAttributesEx',
+        path,
+      );
     }
     final info = fileInfo.ref;
     final attributes = info.dwFileAttributes;
@@ -530,7 +605,7 @@ final class WindowsFileSystem extends FileSystem {
     );
     if (f == win32.INVALID_HANDLE_VALUE) {
       final errorCode = win32.GetLastError();
-      throw _getError(errorCode, 'open failed', path);
+      throw _getError('open failed', errorCode, 'CreateFile', path);
     }
     try {
       // The result of `GetFileSize` is not defined for non-seeking devices
@@ -574,7 +649,7 @@ final class WindowsFileSystem extends FileSystem {
             errorCode == win32.ERROR_SUCCESS) {
           return builder.takeBytes();
         }
-        throw _getError(errorCode, 'read failed', path);
+        throw _getError('read failed', errorCode, 'ReadFile', path);
       }
 
       if (bytesRead.value == 0) {
@@ -605,7 +680,7 @@ final class WindowsFileSystem extends FileSystem {
               ) ==
               win32.FALSE) {
             final errorCode = win32.GetLastError();
-            throw _getError(errorCode, 'read failed', path);
+            throw _getError('read failed', errorCode, 'ReadFile', path);
           }
           bufferOffset += bytesRead.value;
           if (bytesRead.value == 0) {
@@ -651,13 +726,18 @@ final class WindowsFileSystem extends FileSystem {
     );
     if (h == win32.INVALID_HANDLE_VALUE) {
       final errorCode = win32.GetLastError();
-      throw _getError(errorCode, 'CreateFile failed', path);
+      throw _getError('same failed', errorCode, 'CreateFile', path);
     }
     try {
       final info = arena<win32.BY_HANDLE_FILE_INFORMATION>();
       if (win32.GetFileInformationByHandle(h, info) == win32.FALSE) {
         final errorCode = win32.GetLastError();
-        throw _getError(errorCode, 'GetFileInformationByHandle failed', path);
+        throw _getError(
+          'same failed',
+          errorCode,
+          'GetFileInformationByHandle',
+          path,
+        );
       }
       return info.ref;
     } finally {
@@ -673,7 +753,7 @@ final class WindowsFileSystem extends FileSystem {
       final length = win32.GetTempPath2(maxLength, buffer);
       if (length == 0) {
         final errorCode = win32.GetLastError();
-        throw _getError(errorCode, 'GetTempPath failed');
+        throw _getError('temporaryDirectory failed', errorCode, 'GetTempPath2');
       }
       return p.canonicalize(buffer.toDartString());
     } finally {
@@ -710,7 +790,7 @@ final class WindowsFileSystem extends FileSystem {
     );
     if (f == win32.INVALID_HANDLE_VALUE) {
       final errorCode = win32.GetLastError();
-      throw _getError(errorCode, 'open failed', path);
+      throw _getError('write failed', errorCode, 'open failed', path);
     }
 
     try {
@@ -731,7 +811,7 @@ final class WindowsFileSystem extends FileSystem {
             ) ==
             win32.FALSE) {
           final errorCode = win32.GetLastError();
-          throw _getError(errorCode, 'write failed', path);
+          throw _getError('write failed', errorCode, 'WriteFile', path);
         }
 
         remaining -= bytesWritten.value;

pkgs/io_file/lib/src/web_file_system_property.dart

@@ -2,9 +2,10 @@
 // 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 'fake_posix_file_system.dart';
 import 'file_system.dart';
 
+FileSystem? _fileSystem;
+
 /// Return the default [FileSystem] for the current platform.
-FileSystem get fileSystem {
-  throw UnsupportedError('fileSystem');
-}
+FileSystem get fileSystem => _fileSystem ??= FakePosixFileSystem();

pkgs/io_file/test/create_directory_test.dart

@@ -2,86 +2,101 @@
 // 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('vm')
-library;
-
-import 'dart:io';
-
+import 'package:errno/errno.dart';
 import 'package:io_file/io_file.dart';
+import 'package:io_file/src/fake_posix_file_system.dart';
+import 'package:io_file/windows_file_system.dart';
 import 'package:test/test.dart';
-import 'package:win32/win32.dart' as win32;
 
 import 'errors.dart' as errors;
 import 'test_utils.dart';
+import 'test_utils_self.dart' show SelfTestUtils;
 
-void main() {
+void testDirectory(FileSystem fs, TestUtils testUtils) {
   group('createDirectory', () {
     late String tmp;
 
-    setUp(() => tmp = createTemp('createDirectory'));
+    setUp(() => tmp = testUtils.createTestDirectory('createDirectory'));
 
-    tearDown(() => deleteTemp(tmp));
+    tearDown(() => testUtils.deleteDirectoryTree(tmp));
 
     //TODO(brianquinlan): test with a very long path.
 
     test('success', () {
       final path = '$tmp/dir';
 
-      fileSystem.createDirectory(path);
-      expect(FileSystemEntity.isDirectorySync(path), isTrue);
+      fs.createDirectory(path);
+      expect(testUtils.isDir(path), isTrue);
     });
 
     test('create in non-existent directory', () {
       final path = '$tmp/foo/dir';
 
       expect(
-        () => fileSystem.createDirectory(path),
+        () => fs.createDirectory(path),
         throwsA(
           isA<PathNotFoundException>()
               .having((e) => e.message, 'message', 'create directory failed')
               .having(
-                (e) => e.osError?.errorCode,
+                (e) => e.systemCall?.errorCode,
                 'errorCode',
-                Platform.isWindows ? win32.ERROR_PATH_NOT_FOUND : errors.enoent,
+                fs is WindowsFileSystem
+                    ? WindowsErrors.pathNotFound
+                    : errors.enoent,
               ),
         ),
       );
     });
 
     test('create over existing directory', () {
       final path = '$tmp/dir';
-      Directory(path).createSync();
+      testUtils.createDirectory(path);
 
       expect(
-        () => fileSystem.createDirectory(path),
+        () => fs.createDirectory(path),
         throwsA(
           isA<PathExistsException>()
               .having((e) => e.message, 'message', 'create directory failed')
               .having(
-                (e) => e.osError?.errorCode,
+                (e) => e.systemCall?.errorCode,
                 'errorCode',
-                Platform.isWindows ? win32.ERROR_ALREADY_EXISTS : errors.eexist,
+                fs is WindowsFileSystem
+                    ? WindowsErrors.alreadyExists
+                    : errors.eexist,
               ),
         ),
       );
     });
 
     test('create over existing file', () {
       final path = '$tmp/file';
-      File(path).createSync();
+      testUtils.createTextFile(path, 'Hello World!');
 
       expect(
-        () => fileSystem.createDirectory(path),
+        () => fs.createDirectory(path),
         throwsA(
           isA<PathExistsException>()
               .having((e) => e.message, 'message', 'create directory failed')
               .having(
-                (e) => e.osError?.errorCode,
+                (e) => e.systemCall?.errorCode,
                 'errorCode',
-                Platform.isWindows ? win32.ERROR_ALREADY_EXISTS : errors.eexist,
+                fs is WindowsFileSystem
+                    ? WindowsErrors.alreadyExists
+                    : errors.eexist,
               ),
         ),
       );
     });
   });
 }
+
+void main() {
+  group('default', () {
+    testDirectory(fileSystem, testUtils());
+  });
+
+  group('fake', () {
+    final fs = FakePosixFileSystem();
+    testDirectory(fs, SelfTestUtils(fs));
+  });
+}

pkgs/io_file/test/errors.dart

@@ -2,21 +2,21 @@
 // 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:io';
 import 'package:errno/errno.dart';
 
-int get eaccess => Platform.isMacOS ? DarwinErrors.eacces : LinuxErrors.eacces;
+// true
 
-int get eexist => Platform.isMacOS ? DarwinErrors.eexist : LinuxErrors.eexist;
+int get eaccess => true ? DarwinErrors.eacces : LinuxErrors.eacces;
 
-int get eisdir => Platform.isMacOS ? DarwinErrors.eisdir : LinuxErrors.eisdir;
+int get eexist => true ? DarwinErrors.eexist : LinuxErrors.eexist;
 
-int get enoent => Platform.isMacOS ? DarwinErrors.enoent : LinuxErrors.enoent;
+int get eisdir => true ? DarwinErrors.eisdir : LinuxErrors.eisdir;
 
-int get enotdir =>
-    Platform.isMacOS ? DarwinErrors.enotdir : LinuxErrors.enotdir;
+int get enoent => true ? DarwinErrors.enoent : LinuxErrors.enoent;
 
-int get enotempty =>
-    Platform.isMacOS ? DarwinErrors.enotempty : LinuxErrors.enotempty;
+int get enotdir => true ? DarwinErrors.enotdir : LinuxErrors.enotdir;
 
-int get eperm => Platform.isMacOS ? DarwinErrors.eperm : LinuxErrors.eperm;
+int get enotempty => true ? DarwinErrors.enotempty : LinuxErrors.enotempty;
+
+int get eperm => true ? DarwinErrors.eperm : LinuxErrors.eperm;

pkgs/io_file/test/metadata_apple_test.dart

@@ -9,7 +9,7 @@ import 'dart:ffi';
 import 'dart:io';
 
 import 'package:ffi/ffi.dart';
-import 'package:io_file/src/vm_posix_file_system.dart';
+import 'package:io_file/src/native_posix_file_system.dart';
 import 'package:stdlibc/stdlibc.dart' as stdlibc;
 import 'package:test/test.dart';
 

pkgs/io_file/test/test_utils.dart

@@ -2,13 +2,17 @@
 // 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:math';
 import 'dart:typed_data';
+export 'test_utils_self.dart'
+    if (dart.library.io) 'test_utils_native.dart'
+    show testUtils;
 
+/*
 String createTemp(String testName) =>
     Directory.systemTemp.createTempSync(testName).absolute.path;
 void deleteTemp(String path) => Directory(path).deleteSync(recursive: true);
+*/
 
 Uint8List randomUint8List(int length, {int? seed}) {
   final random = Random(seed);
@@ -18,3 +22,14 @@ Uint8List randomUint8List(int length, {int? seed}) {
   }
   return l;
 }
+
+abstract interface class TestUtils {
+  String createTestDirectory(String testName);
+  void deleteDirectoryTree(String path);
+
+  bool isDir(String path);
+
+  void createDirectory(String path);
+
+  void createTextFile(String path, String s);
+}

pkgs/io_file/test/test_utils_native.dart

@@ -0,0 +1,24 @@
+import 'dart:io';
+
+import 'test_utils.dart';
+
+class NativeTestUtils implements TestUtils {
+  @override
+  String createTestDirectory(String testName) =>
+      Directory.systemTemp.createTempSync(testName).absolute.path;
+
+  @override
+  void deleteDirectoryTree(String path) =>
+      Directory(path).deleteSync(recursive: true);
+
+  @override
+  bool isDir(String path) => FileSystemEntity.isDirectorySync(path);
+
+  @override
+  void createDirectory(String path) => Directory(path).createSync();
+
+  @override
+  void createTextFile(String path, String s) => File(path).writeAsStringSync(s);
+}
+
+TestUtils testUtils() => NativeTestUtils();

pkgs/io_file/test/test_utils_self.dart

@@ -0,0 +1,33 @@
+import 'package:io_file/io_file.dart';
+
+import 'test_utils.dart';
+
+class SelfTestUtils implements TestUtils {
+  final FileSystem fs;
+
+  SelfTestUtils([FileSystem? fs]) : fs = fs ?? fileSystem;
+
+  @override
+  void createDirectory(String path) {
+    fs.createDirectory(path);
+  }
+
+  @override
+  String createTestDirectory(String testName) =>
+      fs.createTemporaryDirectory(prefix: testName);
+
+  @override
+  void createTextFile(String path, String s) {
+    fs.writeAsString(path, s);
+  }
+
+  @override
+  void deleteDirectoryTree(String path) {
+    fs.removeDirectoryTree(path);
+  }
+
+  @override
+  bool isDir(String path) => fs.metadata(path).isDirectory;
+}
+
+TestUtils testUtils() => SelfTestUtils();