Add support for listing to the glob package.

pkg/glob/lib/src/list_tree.dart

Index: pkg/glob/lib/src/list_tree.dart
diff --git a/pkg/glob/lib/src/list_tree.dart b/pkg/glob/lib/src/list_tree.dart
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+++ b/pkg/glob/lib/src/list_tree.dart
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+// 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 glob.list_tree;
+
+import 'dart:io';
+import 'dart:async';
+
+import 'package:path/path.dart' as p;
+
+import 'ast.dart';
+import 'stream_pool.dart';
+
+/// A structure built from a glob that efficiently lists filesystem entities
+/// that match that glob.
+///
+/// This structure is designed to list the minimal number of physical
+/// directories necessary to find everything that matches the glob. For example,
+/// for the glob `foo/{bar,baz}/*`, there's no need to list the working
+/// directory or even `foo/`; only `foo/bar` and `foo/baz` should be listed.
+///
+/// This works by creating a tree of [_ListTreeNode]s, each of which corresponds
+/// to a single of directory nesting in the source glob. Each node has child
+/// nodes associated with globs ([_ListTreeNode.children]), as well as its own
+/// glob ([_ListTreeNode._validator]) that indicates which entities within that
+/// node's directory should be returned.
+///
+/// For example, the glob `foo/{*.dart,b*/*.txt}` creates the following tree:
+///
+///     .
+///     '-- "foo" (validator: "*.dart")
+///         '-- "b*" (validator: "*.txt"
+///
+/// If a node doesn't have a validator, we know we don't have to list it
+/// explicitly.
+///
+/// Nodes can also be marked as "recursive", which means they need to be listed
+/// recursively (usually to support `**`). In this case, they will have no
+/// children; instead, their validator will just encompass the globs that would
+/// otherwise be in their children. For example, the glob
+/// `foo/{**.dart,bar/*.txt}` creates a recursive node for `foo` with the
+/// validator `**.dart,bar/*.txt`.
+///
+/// If the glob contains multiple filesystem roots (e.g. `{C:/,D:/}*.dart`),
+/// each root will have its own tree of nodes. Relative globs use `.` as their
+/// root instead.
+class ListTree {
+  /// A map from filesystem roots to the list tree for those roots.
+  ///
+  /// A relative glob will use `.` as its root.
+  final _trees = new Map<String, _ListTreeNode>();
+
+  /// Whether paths listed might overlap.
+  ///
+  /// If they do, we need to filter out overlapping paths.
+  bool _canOverlap;
+
+  ListTree(AstNode glob) {
+    // The first step in constructing a tree from the glob is to simplify the
+    // problem by eliminating options. [glob.flattenOptions] bubbles all options
+    // (and certain ranges) up to the top level of the glob so we can deal with
+    // them one at a time.
+    var options = glob.flattenOptions();
+
+    for (var option in options.options) {
+      // Since each option doesn't include its own options, we can safely split
+      // it into path components.
+      var components = option.split(p.context);
+      var firstNode = components.first.nodes.first;
+      var root = '.';
+
+      // Determine the root for this option, if it's absolute. If it's not, the
+      // root's just ".".
+      if (firstNode is LiteralNode) {
+        var text = firstNode.text;
+        if (Platform.isWindows) text.replaceAll("/", "\\");
+        if (p.isAbsolute(text)) {
+          // If the path is absolute, the root should be the only thing in the
+          // first component.
+          assert(components.first.nodes.length == 1);
+          root = firstNode.text;
+          components.removeAt(0);
+        }
+      }
+
+      _addGlob(root, components);
+    }
+
+    _canOverlap = _computeCanOverlap();
+  }
+
+  /// Add the glob represented by [components] to the tree under [root].
+  void _addGlob(String root, List<AstNode> components) {
+    // The first [parent] represents the root directory itself. It may be null
+    // here if this is the first option with this particular [root]. If so,
+    // we'll create it below.
+    //
+    // As we iterate through [components], [parent] will be set to
+    // progressively more nested nodes.
+    var parent = _trees[root];
+    for (var i = 0; i < components.length; i++) {
+      var component = components[i];
+      var recursive = component.nodes.any((node) => node is DoubleStarNode);
+      var complete = i == components.length - 1;
+
+      // If the parent node for this level of nesting already exists, the new
+      // option will be added to it as additional validator options and/or
+      // additional children.
+      //
+      // If the parent doesn't exist, we'll create it in one of the else
+      // clauses below.
+      if (parent != null) {
+        if (parent.isRecursive || recursive) {
+          // If [component] is recursive, mark [parent] as recursive. This
+          // will cause all of its children to be folded into its validator.
+          // If [parent] was already recursive, this is a no-op.
+          parent.makeRecursive();
+
+          // Add [component] and everything nested beneath it as an option to
+          // [parent]. Since [parent] is recursive, it will recursively list
+          // everything beneath it and filter them with one big glob.
+          parent.addOption(_join(components.sublist(i)));
+          return;
+        } else if (complete) {
+          // If [component] is the last component, add it to [parent]'s
+          // validator but not to its children.
+          parent.addOption(component);
+        } else {
+          // On the other hand if there are more components, add [component]
+          // to [parent]'s children and not its validator. Since we process
+          // each option's components separately, the same component is never
+          // both a validator and a child.
+          if (!parent.children.containsKey(component)) {
+            parent.children[component] = new _ListTreeNode();
+          }
+          parent = parent.children[component];
+        }
+      } else if (recursive) {
+        _trees[root] = new _ListTreeNode.recursive(
+            _join(components.sublist(i)));
+        return;
+      } else if (complete) {
+        _trees[root] = new _ListTreeNode()..addOption(component);
+      } else {
+        _trees[root] = new _ListTreeNode();
+        _trees[root].children[component] = new _ListTreeNode();
+        parent = _trees[root].children[component];
+      }
+    }
+  }
+
+  /// Computes the value for [_canOverlap].
+  bool _computeCanOverlap() {
+    // If this can list a relative path and an absolute path, the former may be
+    // contained within the latter.
+    if (_trees.length > 1 && _trees.containsKey('.')) return true;
+
+    // Otherwise, this can only overlap if the tree beneath any given root could
+    // overlap internally.
+    return _trees.values.any((node) => node.canOverlap);
+  }
+
+  /// List all entities that match this glob beneath [root].
+  Stream<FileSystemEntity> list({String root, bool followLinks: true}) {
+    if (root == null) root = '.';
+    var pool = new StreamPool();
+    for (var rootDir in _trees.keys) {
+      var dir = rootDir == '.' ? root : rootDir;
+      pool.add(_trees[rootDir].list(dir, followLinks: followLinks));
+    }
+    pool.closeWhenEmpty();
+
+    if (!_canOverlap) return pool.stream;
+
+    // TODO(nweiz): Rather than filtering here, avoid double-listing directories
+    // in the first place.
+    var seen = new Set();
+    return pool.stream.where((entity) {
+      if (seen.contains(entity.path)) return false;
+      seen.add(entity.path);
+      return true;
+    });
+  }
+
+  /// Synchronosuly list all entities that match this glob beneath [root].
+  List<FileSystemEntity> listSync({String root, bool followLinks: true}) {
+    if (root == null) root = '.';
+
+    var result = _trees.keys.expand((rootDir) {
+      var dir = rootDir == '.' ? root : rootDir;
+      return _trees[rootDir].listSync(dir, followLinks: followLinks);
+    });
+
+    if (!_canOverlap) return result.toList();
+
+    // TODO(nweiz): Rather than filtering here, avoid double-listing directories
+    // in the first place.
+    var seen = new Set();
+    return result.where((entity) {
+      if (seen.contains(entity.path)) return false;
+      seen.add(entity.path);
+      return true;
+    }).toList();
+  }
+}
+
+/// A single node in a [ListTree].
+class _ListTreeNode {
+  /// This node's child nodes, by their corresponding globs.
+  ///
+  /// Each child node will only be listed on directories that match its glob.
+  ///
+  /// This may be `null`, indicating that this node should be listed
+  /// recursively.
+  Map<SequenceNode, _ListTreeNode> children;
+
+  /// This node's validator.
+  ///
+  /// This determines which entities will ultimately be emitted when [list] is
+  /// called.
+  OptionsNode _validator;
+
+  /// Whether this node is recursive.
+  ///
+  /// A recursive node has no children and is listed recursively.
+  bool get isRecursive => children == null;
+
+  /// Whether this node doesn't itself need to be listed.
+  ///
+  /// If a node has no validator and all of its children are literal filenames,
+  /// there's no need to list its contents. We can just directly traverse into
+  /// its children.
+  bool get _isIntermediate {
+    if (_validator != null) return false;
+    return children.keys.every((sequence) =>
+        sequence.nodes.length == 1 && sequence.nodes.first is LiteralNode);
+  }
+
+  /// Returns whether listing this node might return overlapping results.
+  bool get canOverlap {
+    // A recusive node can never overlap with itself, because it will only ever
+    // involve a single call to [Directory.list] that's then filtered with
+    // [_validator].
+    if (isRecursive) return false;
+
+    // If there's more than one child node and at least one of the children is
+    // dynamic (that is, matches more than just a literal string), there may be
+    // overlap.
+    if (children.length > 1 && children.keys.any((sequence) =>
+          sequence.nodes.length > 1 || sequence.nodes.single is! LiteralNode)) {
+      return true;
+    }
+
+    return children.values.any((node) => node.canOverlap);
+  }
+
+  /// Creates a node with no children and no validator.
+  _ListTreeNode()
+      : children = new Map<SequenceNode, _ListTreeNode>(),
+        _validator = null;
+
+  /// Creates a recursive node the given [validator].
+  _ListTreeNode.recursive(SequenceNode validator)
+      : children = null,
+        _validator = new OptionsNode([validator]);
+
+  /// Transforms this into recursive node, folding all its children into its
+  /// validator.
+  void makeRecursive() {
+    if (isRecursive) return;
+    _validator = new OptionsNode(children.keys.map((sequence) {
+      var child = children[sequence];
+      child.makeRecursive();
+      return _join([sequence, child._validator]);
+    }));
+    children = null;
+  }
+
+  /// Adds [validator] to this node's existing validator.
+  void addOption(SequenceNode validator) {
+    if (_validator == null) {
+      _validator = new OptionsNode([validator]);
+    } else {
+      _validator.options.add(validator);
+    }
+  }
+
+  /// Lists all entities within [dir] matching this node or its children.
+  ///
+  /// This may return duplicate entities. These will be filtered out in
+  /// [ListTree.list].
+  Stream<FileSystemEntity> list(String dir, {bool followLinks: true}) {
+    if (isRecursive) {
+      return new Directory(dir).list(recursive: true, followLinks: followLinks)
+          .where((entity) => _matches(entity.path.substring(dir.length + 1)));
+    }
+
+    var resultPool = new StreamPool();
+
+    // Don't spawn extra [Directory.list] calls when we already know exactly
+    // which subdirectories we're interested in.
+    if (_isIntermediate) {
+      children.forEach((sequence, child) {
+        resultPool.add(child.list(p.join(dir, sequence.nodes.single.text),
+            followLinks: followLinks));
+      });
+      resultPool.closeWhenEmpty();
+      return resultPool.stream;
+    }
+
+    var resultController = new StreamController(sync: true);
+    resultPool.add(resultController.stream);
+    new Directory(dir).list(followLinks: followLinks).listen((entity) {
+      var basename = entity.path.substring(dir.length + 1);
+      if (_matches(basename)) resultController.add(entity);
+
+      children.forEach((sequence, child) {
+        if (entity is! Directory) return;
+        if (!sequence.matches(basename)) return;
+        resultPool.add(child.list(p.join(dir, basename),
+            followLinks: followLinks));
+      });
+    },
+        onError: resultController.addError,
+        onDone: resultController.close);
+
+    resultPool.closeWhenEmpty();
+    return resultPool.stream;
+  }
+
+  /// Synchronously lists all entities within [dir] matching this node or its
+  /// children.
+  ///
+  /// This may return duplicate entities. These will be filtered out in
+  /// [ListTree.listSync].
+  Iterable<FileSystemEntity> listSync(String dir, {bool followLinks: true}) {
+    if (isRecursive) {
+      return new Directory(dir)
+          .listSync(recursive: true, followLinks: followLinks)
+          .where((entity) => _matches(entity.path.substring(dir.length + 1)));
+    }
+
+    // Don't spawn extra [Directory.listSync] calls when we already know exactly
+    // which subdirectories we're interested in.
+    if (_isIntermediate) {
+      return children.keys.expand((sequence) {
+        return children[sequence].listSync(
+            p.join(dir, sequence.nodes.single.text), followLinks: followLinks);
+      });
+    }
+
+    return new Directory(dir).listSync(followLinks: followLinks)
+        .expand((entity) {
+      var entities = [];
+      var basename = entity.path.substring(dir.length + 1);
+      if (_matches(basename)) entities.add(entity);
+      if (entity is! Directory) return entities;
+
+      entities.addAll(children.keys
+          .where((sequence) => sequence.matches(basename))
+          .expand((sequence) {
+        return children[sequence].listSync(
+            p.join(dir, basename), followLinks: followLinks);
+      }));
+
+      return entities;
+    });
+  }
+
+  /// Returns whether the native [path] matches [_validator].
+  bool _matches(String path) {
+    if (_validator == null) return false;
+    return _validator.matches(path);
+  }
+
+  String toString() => "($_validator) $children";
+}
+
+/// Joins each [components] into a new glob where each component is separated by
+/// a path separator.
+SequenceNode _join(Iterable<AstNode> components) {
+  var componentsList = components.toList();
+  var nodes = [componentsList.removeAt(0)];
+  for (var component in componentsList) {
+    nodes.add(new LiteralNode('/'));
+    nodes.add(component);
+  }
+  return new SequenceNode(nodes);
+}