Move source maps package to the dart repo, so it can be used by other internal

pkg/source_maps/lib/parser.dart

+// Copyright (c) 2013, 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.
+
+/// Contains the top-level function to parse source maps version 3.
+library source_maps.parser;
+
+import 'dart:json' as json;
+
+import 'span.dart';
+import 'src/utils.dart';
+import 'src/vlq.dart';
+
+/// Parses a source map directly from a json string.
+// TODO(sigmund): evaluate whether other maps should have the json parsed, or
+// the string represenation.
+Mapping parse(String jsonMap, {Map<String, Map> otherMaps}) =>
+  parseJson(json.parse(jsonMap), otherMaps: otherMaps);
+
+/// Parses a source map directly from a json map object.
+Mapping parseJson(Map map, {Map<String, Map> otherMaps}) {
+  if (map['version'] != 3) {
+    throw new ArgumentError(
+        'unexpected source map version: ${map["version"]}. '
+        'Only version 3 is supported.');
+  }
+
+  // TODO(sigmund): relax this? dart2js doesn't generate the file entry.
+  if (!map.containsKey('file')) {
+    throw new ArgumentError('missing "file" in source map');
+  }
+
+  if (map.containsKey('sections')) {
+    if (map.containsKey('mappings') || map.containsKey('sources') ||
+        map.containsKey('names')) {
+      throw new FormatException('map containing "sections" '
+          'cannot contain "mappings", "sources", or "names".');
+    }
+    return new MultiSectionMapping.fromJson(map['sections'], otherMaps);
+  }
+  return new SingleMapping.fromJson(map);
+}
+
+
+/// A mapping parsed our of a source map.
+abstract class Mapping {
+  Span spanFor(int line, int column, {Map<String, SourceFile> files});
+
+  Span spanForLocation(Location loc, {Map<String, SourceFile> files}) {
+    return spanFor(loc.line, loc.column, files: files);
+  }
+}
+
+/// A meta-level map containing sections.
+class MultiSectionMapping extends Mapping {
+  /// For each section, the start line offset.
+  final List<int> _lineStart = <int>[];
+
+  /// For each section, the start column offset.
+  final List<int> _columnStart = <int>[];
+
+  /// For each section, the actual source map information, which is not adjusted
+  /// for offsets.
+  final List<Mapping> _maps = <Mapping>[];
+
+  /// Creates a section mapping from json.
+  MultiSectionMapping.fromJson(List sections, Map<String, Map> otherMaps) {
+    for (var section in sections) {
+      var offset = section['offset'];
+      if (offset == null) throw new FormatException('section missing offset');
+
+      var line = section['offset']['line'];
+      if (line == null) throw new FormatException('offset missing line');
+
+      var column = section['offset']['column'];
+      if (column == null) throw new FormatException('offset missing column');
+
+      _lineStart.add(line);
+      _columnStart.add(column);
+
+      var url = section['url'];
+      var map = section['map'];
+
+      if (url != null && map != null) {
+        throw new FormatException("section can't use both url and map entries");
+      } else if (url != null) {
+        if (otherMaps == null || otherMaps[url] == null) {
+          throw new FormatException(
+              'section contains refers to $url, but no map was '
+              'given for it. Make sure a map is passed in "otherMaps"');
+        }
+        _maps.add(parseJson(otherMaps[url], otherMaps: otherMaps));
+      } else if (map != null) {
+        _maps.add(parseJson(map, otherMaps: otherMaps));
+      } else {
+        throw new FormatException('section missing url or map');
+      }
+    }
+    if (_lineStart.length == 0) {
+      throw new FormatException('expected at least one section');
+    }
+  }
+
+  int _indexFor(line, column) {
+    for(int i = 0; i < _lineStart.length; i++) {
+      if (line < _lineStart[i]) return i - 1;
+      if (line == _lineStart[i] && column < _columnStart[i]) return i - 1;
+    }
+    return _lineStart.length - 1;
+  }
+
+  Span spanFor(int line, int column, {Map<String, SourceFile> files}) {
+    int index = _indexFor(line, column);
+    return _maps[index].spanFor(
+        line - _lineStart[index], column - _columnStart[index], files: files);
+  }
+
+  String toString() {
+    var buff = new StringBuffer("$runtimeType : [");
+    for (int i = 0; i < _lineStart.length; i++) {
+      buff..write('(')
+          ..write(_lineStart[i])
+          ..write(',')
+          ..write(_columnStart[i])
+          ..write(':')
+          ..write(_maps[i])
+          ..write(')');
+    }
+    buff.write(']');
+    return buff.toString();
+  }
+}
+
+/// A map containing direct source mappings.
+// TODO(sigmund): integrate mapping and sourcemap builder?
+class SingleMapping extends Mapping {
+  /// Url of the target file.
+  final String targetUrl;
+
+  /// Source urls used in the mapping, indexed by id.
+  final List<String> urls;
+
+  /// Source names used in the mapping, indexed by id.
+  final List<String> names;
+
+  /// Entries indicating the beginning of each span.
+  final List<TargetLineEntry> lines = <TargetLineEntry>[];
+
+  SingleMapping.fromJson(Map map)
+      : targetUrl = map['file'],
+        // TODO(sigmund): add support for 'sourceRoot'
+        urls = map['sources'],
+        names = map['names'] {
+    int line = 0;
+    int column = 0;
+    int srcUrlId = 0;
+    int srcLine = 0;
+    int srcColumn = 0;
+    int srcNameId = 0;
+    var tokenizer = new _MappingTokenizer(map['mappings']);
+    var entries = <TargetEntry>[];
+
+    while (tokenizer.hasTokens) {
+      if (tokenizer.nextKind.isNewLine) {
+        if (!entries.isEmpty) {
+          lines.add(new TargetLineEntry(line, entries));
+          entries = <TargetEntry>[];
+        }
+        line++;
+        column = 0;
+        tokenizer._consumeNewLine();
+        continue;
+      }
+
+      // Decode the next entry, using the previous encountered values to
+      // decode the relative values.
+      //
+      // We expect 1, 4, or 5 values. If present, values are expected in the
+      // following order:
+      //   0: the starting column in the current line of the generated file
+      //   1: the id of the original source file
+      //   2: the starting line in the original source
+      //   3: the starting column in the original source
+      //   4: the id of the original symbol name
+      // The values are relative to the previous encountered values.
+      if (tokenizer.nextKind.isNewSegment) throw _segmentError(0, line);
+      column += tokenizer._consumeValue();
+      if (!tokenizer.nextKind.isValue) {
+        entries.add(new TargetEntry(column));
+      } else {
+        srcUrlId += tokenizer._consumeValue();
+        if (srcUrlId >= urls.length) {
+          throw new StateError(
+              'Invalid source url id. $targetUrl, $line, $srcUrlId');
+        }
+        if (!tokenizer.nextKind.isValue) throw _segmentError(2, line);
+        srcLine += tokenizer._consumeValue();
+        if (!tokenizer.nextKind.isValue) throw _segmentError(3, line);
+        srcColumn += tokenizer._consumeValue();
+        if (!tokenizer.nextKind.isValue) {
+          entries.add(new TargetEntry(column, srcUrlId, srcLine, srcColumn));
+        } else {
+          srcNameId += tokenizer._consumeValue();
+          if (srcNameId >= names.length) {
+            throw new StateError(
+                'Invalid name id: $targetUrl, $line, $srcNameId');
+          }
+          entries.add(
+              new TargetEntry(column, srcUrlId, srcLine, srcColumn, srcNameId));
+        }
+      }
+      if (tokenizer.nextKind.isNewSegment) tokenizer._consumeNewSegment();
+    }
+    if (!entries.isEmpty) {
+      lines.add(new TargetLineEntry(line, entries));
+    }
+  }
+
+  _segmentError(int seen, int line) => new StateError(
+      'Invalid entry in sourcemap, expected 1, 4, or 5'
+      ' values, but got $seen.\ntargeturl: $targetUrl, line: $line');
+
+  /// Returns [TargetLineEntry] which includes the location in the target [line]
+  /// number. In particular, the resulting entry is the last entry whose line
+  /// number is lower or equal to [line].
+  TargetLineEntry _findLine(int line) {
+    int index = binarySearch(lines, (e) => e.line > line);
+    return (index <= 0) ? null : lines[index - 1];
+  }
+
+  /// Returns [TargetEntry] which includes the location denoted by
+  /// [line], [column]. If [lineEntry] corresponds to [line], then this will be
+  /// the last entry whose column is lower or equal than [column]. If
+  /// [lineEntry] corresponds to a line prior to [line], then the result will be
+  /// the very last entry on that line.
+  TargetEntry _findColumn(int line, int column, TargetLineEntry lineEntry) {
+    if (lineEntry == null || lineEntry.entries.length == 0) return null;
+    if (lineEntry.line != line) return lineEntry.entries.last;
+    var entries = lineEntry.entries;
+    int index = binarySearch(entries, (e) => e.column > column);
+    return (index <= 0) ? null : entries[index - 1];
+  }
+
+  Span spanFor(int line, int column, {Map<String, SourceFile> files}) {
+    var lineEntry = _findLine(line);
+    var entry = _findColumn(line, column, _findLine(line));
+    if (entry == null) return null;
+    var url = urls[entry.sourceUrlId];
+    if (files != null && files[url] != null) {
+      var file = files[url];
+      var start = file.getOffset(entry.sourceLine, entry.sourceColumn);
+      if (entry.sourceNameId != null) {
+        var text = names[entry.sourceNameId];
+        return new FileSpan(files[url], start, start + text.length, true);
+      } else {
+        return new FileSpan(files[url], start);
+      }
+    } else {
+      // Offset and other context is not available.
+      if (entry.sourceNameId != null) {
+        return new FixedSpan(url, 0, entry.sourceLine, entry.sourceColumn,
+            text: names[entry.sourceNameId], isIdentifier: true);
+      } else {
+        return new FixedSpan(url, 0, entry.sourceLine, entry.sourceColumn);
+      }
+    }
+  }
+
+  String toString() {
+    return (new StringBuffer("$runtimeType : [")
+        ..write('targetUrl: ')
+        ..write(targetUrl)
+        ..write(', urls: ')
+        ..write(urls)
+        ..write(', names: ')
+        ..write(names)
+        ..write(', lines: ')
+        ..write(lines)
+        ..write(']')).toString();
+  }
+
+  String get debugString {
+    var buff = new StringBuffer();
+    for (var lineEntry in lines) {
+      var line = lineEntry.line;
+      for (var entry in lineEntry.entries) {
+        buff..write(targetUrl)
+            ..write(': ')
+            ..write(line)
+            ..write(':')
+            ..write(entry.column)
+            ..write('   -->   ')
+            ..write(urls[entry.sourceUrlId])
+            ..write(': ')
+            ..write(entry.sourceLine)
+            ..write(':')
+            ..write(entry.sourceColumn);
+        if (entry.sourceNameId != null) {
+          buff..write(' (')
+              ..write(names[entry.sourceNameId])
+              ..write(')');
+        }
+        buff.write('\n');
+      }
+    }
+    return buff.toString();
+  }
+}
+
+/// A line entry read from a source map.
+class TargetLineEntry {
+  final int line;
+  List<TargetEntry> entries = <TargetEntry>[];
+  TargetLineEntry(this.line, this.entries);
+
+  String toString() => '$runtimeType: $line $entries';
+}
+
+/// A target segment entry read from a source map
+class TargetEntry {
+  final int column;
+  final int sourceUrlId;
+  final int sourceLine;
+  final int sourceColumn;
+  final int sourceNameId;
+  TargetEntry(this.column, [this.sourceUrlId, this.sourceLine,
+      this.sourceColumn, this.sourceNameId]);
+
+  String toString() => '$runtimeType: '
+      '($column, $sourceUrlId, $sourceLine, $sourceColumn, $sourceNameId)';
+}
+
+/** A character iterator over a string that can peek one character ahead. */
+class _MappingTokenizer implements Iterator<String> {
+  final String _internal;
+  final int _length;
+  int index = -1;
+  _MappingTokenizer(String internal)
+      : _internal = internal,
+        _length = internal.length;
+
+  // Iterator API is used by decodeVlq to consume VLQ entries.
+  bool moveNext() => ++index < _length;
+  String get current =>
+      (index >= 0 && index < _length) ?  _internal[index] : null;
+
+  bool get hasTokens => index < _length - 1 && _length > 0;
+
+  _TokenKind get nextKind {
+    if (!hasTokens) return _TokenKind.EOF;
+    var next = _internal[index + 1];
+    if (next == ';') return _TokenKind.LINE;
+    if (next == ',') return _TokenKind.SEGMENT;
+    return _TokenKind.VALUE;
+  }
+
+  int _consumeValue() => decodeVlq(this);
+  void _consumeNewLine() { ++index; }
+  void _consumeNewSegment() { ++index; }
+
+  // Print the state of the iterator, with colors indicating the current
+  // position.
+  String toString() {
+    var buff = new StringBuffer();
+    for (int i = 0; i < index; i++) {
+      buff.write(_internal[i]);
+    }
+    buff.write('');
+    buff.write(current == null ? '' : current);
+    buff.write('');
+    for (int i = index + 1; i < _internal.length; i++) {
+      buff.write(_internal[i]);
+    }
+    buff.write(' ($index)');
+    return buff.toString();
+  }
+}
+
+class _TokenKind {
+  static const _TokenKind LINE = const _TokenKind(isNewLine: true);
+  static const _TokenKind SEGMENT = const _TokenKind(isNewSegment: true);
+  static const _TokenKind EOF = const _TokenKind(isEof: true);
+  static const _TokenKind VALUE = const _TokenKind();
+  final bool isNewLine;
+  final bool isNewSegment;
+  final bool isEof;
+  bool get isValue => !isNewLine && !isNewSegment && !isEof;
+
+  const _TokenKind(
+      {this.isNewLine: false, this.isNewSegment: false, this.isEof: false});
+}