Add first round of tests, and associated bug fixes (flutter#15)

lib/src/backends/local/local_file_system.dart

@@ -14,6 +14,9 @@ class LocalFileSystem extends FileSystem {
   @override
   File file(String path) => new _LocalFile(this, new io.File(path));
 
+  @override
+  Link link(String path) => new _LocalLink(this, new io.Link(path));
+
   @override
   Directory get currentDirectory => directory(io.Directory.current.path);
 

lib/src/backends/memory/memory_file.dart

@@ -58,11 +58,11 @@ class _MemoryFile extends _MemoryFileSystemEntity implements File {
         if (currentSegment == finalSegment) {
           if (child != null) {
             if (_isLink(child)) {
-              StringBuffer ledger = new StringBuffer();
+              List<String> ledger = <String>[];
               child = _resolveLinks(child, () => newPath, ledger: ledger);
               _checkExists(child, () => newPath);
               parent = child.parent;
-              childName = fileSystem._context.basename(ledger.toString());
+              childName = ledger.last;
               assert(parent.children.containsKey(childName));
             }
             if (child.type != expectedType) {
@@ -289,9 +289,8 @@ class _FileSink implements io.IOSink {
   }
 
   @override
-  Future flush() {
+  Future flush() async {
     _checkNotStreaming();
-    return new Future.value();
   }
 
   @override

lib/src/backends/memory/memory_file_system.dart

@@ -56,20 +56,24 @@ class MemoryFileSystem extends FileSystem {
   @override
   File file(String path) => new _MemoryFile(this, path);
 
+  @override
+  Link link(String path) => new _MemoryLink(this, path);
+
   @override
   Directory get currentDirectory => directory(_cwd);
 
   @override
   set currentDirectory(dynamic path) {
     String value;
-    if (path is Directory) {
+    if (path is io.Directory) {
       value = path.path;
     } else if (path is String) {
       value = path;
     } else {
-      throw new TypeError();
+      throw new ArgumentError('Invalid type for "path": ${path?.runtimeType}');
     }
-    value = _context.canonicalize(value);
+
+    value = directory(value).resolveSymbolicLinksSync();
     _Node node = _findNode(value);
     _checkExists(node, () => value);
     _checkIsDir(node, () => value);
@@ -83,7 +87,7 @@ class MemoryFileSystem extends FileSystem {
   @override
   io.FileStat statSync(String path) {
     try {
-      return _findNode(path)?.stat;
+      return _findNode(path)?.stat ?? _MemoryFileStat._notFound;
     } on io.FileSystemException {
       return _MemoryFileStat._notFound;
     }
@@ -95,8 +99,8 @@ class MemoryFileSystem extends FileSystem {
 
   @override
   bool identicalSync(String path1, String path2) {
-    _Node node1 = _findNode(path1);
-    _Node node2 = _findNode(path2);
+    _Node node1 = _findNode(path1, resolveTailLink: true);
+    _Node node2 = _findNode(path2, resolveTailLink: true);
     return node1 != null && node1 == node2;
   }
 
@@ -114,16 +118,13 @@ class MemoryFileSystem extends FileSystem {
   io.FileSystemEntityType typeSync(String path, {bool followLinks: true}) {
     _Node node;
     try {
-      node = _findNode(path);
+      node = _findNode(path, resolveTailLink: followLinks);
     } on io.FileSystemException {
       node = null;
     }
-    if (node = null) {
+    if (node == null) {
       return io.FileSystemEntityType.NOT_FOUND;
     }
-    if (followLinks && _isLink(node)) {
-      node = _resolveLinks(node, () => path);
-    }
     return node.type;
   }
 
@@ -146,8 +147,9 @@ class MemoryFileSystem extends FileSystem {
   ///
   /// If the last element in [path] represents a symbolic link, this will
   /// return the [_LinkNode] node for the link (it will not return the
-  /// node to which the link points). However, directory links in the middle
-  /// of the path will be followed in order to find the node.
+  /// node to which the link points), unless [resolveTailLink] is true.
+  /// Directory links in the middle of the path will be followed in order to
+  /// find the node regardless of the value of [resolveTailLink].
   ///
   /// If [segmentVisitor] is specified, it will be invoked for every path
   /// segment visited along the way starting where the reference (root folder
@@ -164,7 +166,8 @@ class MemoryFileSystem extends FileSystem {
     String path, {
     _Node reference,
     _SegmentVisitor segmentVisitor,
-    StringBuffer pathWithSymlinks,
+    List<String> pathWithSymlinks,
+    bool resolveTailLink: false,
   }) {
     if (path == null) {
       throw new ArgumentError.notNull('path');
@@ -207,12 +210,17 @@ class MemoryFileSystem extends FileSystem {
         if (_isLink(child)) {
           child = _resolveLinks(child, subpath, ledger: pathWithSymlinks);
         } else if (pathWithSymlinks != null) {
-          pathWithSymlinks..write(_separator)..write(basename);
+          pathWithSymlinks..add(_separator)..add(basename);
         }
         _checkIsDir(child, subpath);
         directory = child;
+      } else if (pathWithSymlinks != null) {
+        pathWithSymlinks..add(_separator)..add(basename);
       }
     }
+    if (_isLink(child) && resolveTailLink) {
+      child = _resolveLinks(child, () => path);
+    }
     return child;
   }
 }

lib/src/backends/memory/memory_file_system_entity.dart

@@ -58,12 +58,11 @@ abstract class _MemoryFileSystemEntity implements FileSystemEntity {
 
   @override
   String resolveSymbolicLinksSync() {
-    StringBuffer ledger = new StringBuffer();
-    _Node node = fileSystem._findNode(path, pathWithSymlinks: ledger);
-    if (_isLink(node)) {
-      _resolveLinks(node, () => path, ledger: ledger);
-    }
-    String resolved = ledger.toString();
+    List<String> ledger = <String>[];
+    _Node node = fileSystem._findNode(path,
+        pathWithSymlinks: ledger, resolveTailLink: true);
+    _checkExists(node, () => path);
+    String resolved = ledger.join(_separator);
     if (!isAbsolute) {
       resolved = fileSystem._cwd + resolved;
     }

lib/src/backends/memory/utils.dart

@@ -1,13 +1,14 @@
 part of file.src.backends.memory;
 
 /// Checks if `node.type` returns [io.FileSystemEntityType.FILE].
-bool _isFile(_Node node) => node.type == io.FileSystemEntityType.FILE;
+bool _isFile(_Node node) => node?.type == io.FileSystemEntityType.FILE;
 
 /// Checks if `node.type` returns [io.FileSystemEntityType.DIRECTORY].
-bool _isDirectory(_Node node) => node.type == io.FileSystemEntityType.DIRECTORY;
+bool _isDirectory(_Node node) =>
+    node?.type == io.FileSystemEntityType.DIRECTORY;
 
 /// Checks if `node.type` returns [io.FileSystemEntityType.LINK].
-bool _isLink(_Node node) => node.type == io.FileSystemEntityType.LINK;
+bool _isLink(_Node node) => node?.type == io.FileSystemEntityType.LINK;
 
 /// Tells whether the specified path represents an absolute path.
 bool _isAbsolute(String path) => path.startsWith(_separator);
@@ -46,40 +47,33 @@ bool _isEmpty(String str) => str.isEmpty;
 /// [io.FileSystemException], calling [path] to generate the path.
 ///
 /// If [ledger] is specified, the resolved path to the terminal node will be
-/// appended to the ledger. The path will not be normalized, meaning
-/// `..` and `.` path segments will not be resolved.
+/// appended to the ledger (or overwritten in the ledger if a link target
+/// specified an absolute path). The path will not be normalized, meaning
+/// `..` and `.` path segments may be present.
 _Node _resolveLinks(
   _LinkNode link,
   _PathGenerator path, {
-  StringBuffer ledger,
+  List<String> ledger,
 }) {
   // Record a breadcrumb trail to guard against symlink loops.
   Set<_LinkNode> breadcrumbs = new Set<_LinkNode>();
 
-  List<String> ledgerEntryBuilder = ledger != null ? <String>[''] : null;
   _Node node = link;
   while (_isLink(node)) {
     link = node;
     if (!breadcrumbs.add(node)) {
       throw new io.FileSystemException('Loop found in link chain', path());
     }
-    if (ledgerEntryBuilder != null) {
+    if (ledger != null) {
       if (_isAbsolute(link.target)) {
-        ledgerEntryBuilder.clear;
-        ledgerEntryBuilder.addAll(link.target.split(_separator));
-      } else {
-        if (ledgerEntryBuilder.isNotEmpty) {
-          ledgerEntryBuilder.removeLast();
-        }
-        ledgerEntryBuilder.addAll(link.target.split(_separator));
+        ledger.clear();
+      } else if (ledger.isNotEmpty) {
+        ledger.removeLast();
       }
+      ledger.addAll(link.target.split(_separator));
     }
     node = link.referent;
   }
 
-  if (ledger != null) {
-    ledger.write(ledgerEntryBuilder.join(_separator));
-  }
-
   return node;
 }

lib/src/interface/file_system.dart

@@ -3,6 +3,7 @@ import 'dart:io' as io;
 
 import 'directory.dart';
 import 'file.dart';
+import 'link.dart';
 
 /// A generic representation of a file system.
 ///
@@ -19,6 +20,9 @@ abstract class FileSystem {
   /// Returns a reference to a [File] at [path].
   File file(String path);
 
+  /// Returns a reference to a [Link] at [path].
+  Link link(String path);
+
   /// Creates a directory object pointing to the current working directory.
   Directory get currentDirectory;