Paul Berry
ba241c0c8d
This carries a number of benefits: - It allows the front end to trivially support schemes other than "file:" (e.g. "http:") by allowing the client to supply a FileSystem implementation that handles them. - It is more consistent with the functionality of the ".packages" file (which allows packages to map to any kind of URI). - It allows the "bazel root" feature to be rewritten to use a magic scheme rather than a magic path. (This eliminates concerns about the magic path overlapping with a user's use case). Note that this feature has been renamed to "multi root" since it is sufficiently generic to be applicable to build systems other than Bazel. - It reduces the risk of forgetting to use the front end's FileSystem abstraction to access the file system, since the native file system interfaces do not accept URIs. R=danrubel@google.com Review-Url: https://codereview.chromium.org/2614063007 .
69 lines
2.5 KiB
Dart
69 lines
2.5 KiB
Dart
// Copyright (c) 2016, the Dart project authors. Please see the AUTHORS file
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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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library front_end.file_system;
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import 'dart:async';
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import 'package:path/path.dart' as path;
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/// Abstract interface to file system operations.
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///
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/// All front end interaction with the file system goes through this interface;
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/// this makes it possible for clients to use the front end in a way that
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/// doesn't require file system access (e.g. to run unit tests, or to run
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/// inside a browser).
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///
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/// Not intended to be implemented or extended by clients.
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abstract class FileSystem {
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/// Returns a path context suitable for use with this [FileSystem].
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///
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/// TODO(paulberry): try to eliminate all usages of this. Since the
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/// FileSystem API now uses URIs rather than paths, it should not be needed.
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path.Context get context;
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/// Returns a [FileSystemEntity] corresponding to the given [uri].
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///
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/// Uses of `..` and `.` in the URI are normalized before returning.
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///
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/// If the URI scheme is not supported by this file system, an [Error] will be
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/// thrown.
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///
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/// Does not check whether a file or folder exists at the given location.
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FileSystemEntity entityForUri(Uri uri);
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}
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/// Abstract representation of a file system entity that may or may not exist.
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///
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/// Instances of this class have suitable implementations of equality tests and
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/// hashCode.
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///
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/// Not intended to be implemented or extended by clients.
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abstract class FileSystemEntity {
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/// Returns the absolute normalized URI represented by this file system
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/// entity.
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///
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/// Note: this is not necessarily the same as the URI that was passed to
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/// [FileSystem.entityForUri], since the URI might have been normalized.
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Uri get uri;
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/// Attempts to access this file system entity as a file and read its contents
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/// as raw bytes.
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///
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/// If an error occurs while attempting to read the file (e.g. because no such
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/// file exists, or the entity is a directory), the future is completed with
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/// an [Exception].
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Future<List<int>> readAsBytes();
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/// Attempts to access this file system entity as a file and read its contents
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/// as a string.
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///
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/// The file is assumed to be UTF-8 encoded.
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///
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/// If an error occurs while attempting to read the file (e.g. because no such
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/// file exists, the entity is a directory, or the file is not valid UTF-8),
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/// the future is completed with an [Exception].
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Future<String> readAsString();
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}
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