nweiz@google.com
f1eb09d597
These constructors make it easy to use the same code for extracting data from both YAML and non-YAML objects. R=rnystrom@google.com Review URL: https://codereview.chromium.org//343063002 git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@37665 260f80e4-7a28-3924-810f-c04153c831b5
77 lines
2.6 KiB
Dart
77 lines
2.6 KiB
Dart
// Copyright (c) 2012, 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 yaml.constructor;
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import 'equality.dart';
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import 'model.dart';
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import 'visitor.dart';
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import 'yaml_node.dart';
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/// Takes a parsed and composed YAML document (what the spec calls the
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/// "representation graph") and creates native Dart objects that represent that
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/// document.
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class Constructor extends Visitor {
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/// The root node of the representation graph.
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final Node _root;
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/// Map from anchor names to the most recent Dart node with that anchor.
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final _anchors = <String, YamlNode>{};
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Constructor(this._root);
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/// Runs the Constructor to produce a Dart object.
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YamlNode construct() => _root.visit(this);
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/// Returns the value of a scalar.
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YamlScalar visitScalar(ScalarNode scalar) =>
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new YamlScalar.internal(scalar.value, scalar.span);
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/// Converts a sequence into a List of Dart objects.
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YamlList visitSequence(SequenceNode seq) {
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var anchor = getAnchor(seq);
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if (anchor != null) return anchor;
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var nodes = [];
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var dartSeq = setAnchor(seq, new YamlList.internal(nodes, seq.span));
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nodes.addAll(super.visitSequence(seq));
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return dartSeq;
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}
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/// Converts a mapping into a [Map] of Dart objects.
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YamlMap visitMapping(MappingNode map) {
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var anchor = getAnchor(map);
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if (anchor != null) return anchor;
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var nodes = deepEqualsMap();
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var dartMap = setAnchor(map, new YamlMap.internal(nodes, map.span));
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super.visitMapping(map).forEach((k, v) => nodes[k] = v);
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return dartMap;
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}
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/// Returns a new Dart object wrapping the object that already represents
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/// [anchored], if such a thing exists.
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YamlNode getAnchor(Node anchored) {
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if (anchored.anchor == null) return null;
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var value = _anchors[anchored.anchor];
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if (value == null) return null;
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// Re-wrap [value]'s contents so that it's associated with the span of the
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// anchor rather than its original definition.
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if (value is YamlMap) {
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return new YamlMap.internal(value.nodes, anchored.span);
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} else if (value is YamlList) {
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return new YamlList.internal(value.nodes, anchored.span);
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} else {
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assert(value is YamlScalar);
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return new YamlScalar.internal(value.value, anchored.span);
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}
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}
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/// Records that [value] is the Dart object representing [anchored].
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YamlNode setAnchor(Node anchored, YamlNode value) {
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if (anchored.anchor == null) return value;
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_anchors[anchored.anchor] = value;
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return value;
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}
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}
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