Add observatory_pub_packages snapshot to third_party

observatory_pub_packages/analyzer/file_system/file_system.dart

+// Copyright (c) 2014, 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.
+
+library file_system;
+
+import 'dart:async';
+
+import 'package:analyzer/src/generated/source.dart';
+import 'package:path/path.dart';
+import 'package:watcher/watcher.dart';
+
+
+/**
+ * [File]s are leaf [Resource]s which contain data.
+ */
+abstract class File extends Resource {
+  /**
+   * Create a new [Source] instance that serves this file.
+   */
+  Source createSource([Uri uri]);
+}
+
+
+/**
+ * [Folder]s are [Resource]s which may contain files and/or other folders.
+ */
+abstract class Folder extends Resource {
+  /**
+   * Watch for changes to the files inside this folder (and in any nested
+   * folders, including folders reachable via links).
+   */
+  Stream<WatchEvent> get changes;
+
+  /**
+   * If the path [path] is a relative path, convert it to an absolute path
+   * by interpreting it relative to this folder.  If it is already an aboslute
+   * path, then don't change it.
+   *
+   * However, regardless of whether [path] is relative or absolute, normalize
+   * it by removing path components of the form '.' or '..'.
+   */
+  String canonicalizePath(String path);
+
+  /**
+   * Return `true` if absolute [path] references a resource in this folder.
+   */
+  bool contains(String path);
+
+  /**
+   * Return an existing child [Resource] with the given [relPath].
+   * Return a not existing [File] if no such child exist.
+   */
+  Resource getChild(String relPath);
+
+  /**
+   * Return a list of existing direct children [Resource]s (folders and files)
+   * in this folder, in no particular order.
+   */
+  List<Resource> getChildren();
+}
+
+
+/**
+ * The abstract class [Resource] is an abstraction of file or folder.
+ */
+abstract class Resource {
+  /**
+   * Return `true` if this resource exists.
+   */
+  bool get exists;
+
+  /**
+   * Return the [Folder] that contains this resource, or `null` if this resource
+   * is a root folder.
+   */
+  Folder get parent;
+
+  /**
+   * Return the full path to this resource.
+   */
+  String get path;
+
+  /**
+   * Return a short version of the name that can be displayed to the user to
+   * denote this resource.
+   */
+  String get shortName;
+
+  /**
+   * Return `true` if absolute [path] references this resource or a resource in
+   * this folder.
+   */
+  bool isOrContains(String path);
+}
+
+
+/**
+ * Instances of the class [ResourceProvider] convert [String] paths into
+ * [Resource]s.
+ */
+abstract class ResourceProvider {
+  /**
+   * Get the path context used by this resource provider.
+   */
+  Context get pathContext;
+
+  /**
+   * Return the [Resource] that corresponds to the given [path].
+   */
+  Resource getResource(String path);
+}
+
+
+/**
+ * A [UriResolver] for [Resource]s.
+ */
+class ResourceUriResolver extends UriResolver {
+  /**
+   * The name of the `file` scheme.
+   */
+  static String _FILE_SCHEME = "file";
+
+  final ResourceProvider _provider;
+
+  ResourceUriResolver(this._provider);
+
+  @override
+  Source resolveAbsolute(Uri uri) {
+    if (!_isFileUri(uri)) {
+      return null;
+    }
+    Resource resource = _provider.getResource(_provider.pathContext.fromUri(uri)
+        );
+    if (resource is File) {
+      return resource.createSource(uri);
+    }
+    return null;
+  }
+
+  /**
+   * Return `true` if the given URI is a `file` URI.
+   *
+   * @param uri the URI being tested
+   * @return `true` if the given URI is a `file` URI
+   */
+  static bool _isFileUri(Uri uri) => uri.scheme == _FILE_SCHEME;
+}