Support a much larger subset of YAML.

utils/pub/yaml/parser.dart

 // Copyright (c) 2012, 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.
 
 /**
  * Translates a string of characters into a YAML serialization tree.
  *
  * This parser is designed to closely follow the spec. All productions in the
  * spec are numbered, and the corresponding methods in the parser have the same
  * numbers. This is certainly not the most efficient way of parsing YAML, but it
  * is the easiest to write and read in the context of the spec.
  *
  * Methods corresponding to productions are also named as in the spec,
  * translating the name of the method (although not the annotation characters)
  * into camel-case for dart style.. For example, the spec has a production named
  * `nb-ns-plain-in-line`, and the method implementing it is named
  * `nb_ns_plainInLine`. The exception to that rule is methods that just
  * recognize character classes; these are named `is*`.
  */
 class _Parser {
   static final TAB = 0x9;
   static final LF = 0xA;
   static final CR = 0xD;
   static final SP = 0x20;
   static final TILDE = 0x7E;
   static final NEL = 0x85;
+  static final PLUS = 0x2B;
   static final HYPHEN = 0x2D;
   static final QUESTION_MARK = 0x3F;
   static final COLON = 0x3A;
   static final COMMA = 0x2C;
   static final LEFT_BRACKET = 0x5B;
   static final RIGHT_BRACKET = 0x5D;
   static final LEFT_BRACE = 0x7B;
   static final RIGHT_BRACE = 0x7D;
   static final HASH = 0x23;
   static final AMPERSAND = 0x26;
   static final ASTERISK = 0x2A;
   static final EXCLAMATION = 0x21;
   static final VERTICAL_BAR = 0x7C;
   static final GREATER_THAN = 0x3E;
   static final SINGLE_QUOTE = 0x27;
   static final DOUBLE_QUOTE = 0x22;
   static final PERCENT = 0x25;
   static final AT = 0x40;
   static final GRAVE_ACCENT = 0x60;
 
   static final NULL = 0x0;
   static final BELL = 0x7;
   static final BACKSPACE = 0x8;
   static final VERTICAL_TAB = 0xB;
   static final FORM_FEED = 0xC;
   static final ESCAPE = 0x1B;
+  static final SLASH = 0x2F;
   static final BACKSLASH = 0x5C;
+  static final UNDERSCORE = 0x5F;
   static final NBSP = 0xA0;
   static final LINE_SEPARATOR = 0x2028;
   static final PARAGRAPH_SEPARATOR = 0x2029;
 
+  static final NUMBER_0 = 0x30;
+  static final NUMBER_9 = 0x39;
+
+  static final LETTER_A = 0x61;
+  static final LETTER_B = 0x62;
+  static final LETTER_E = 0x65;
+  static final LETTER_F = 0x66;
+  static final LETTER_N = 0x6E;
+  static final LETTER_R = 0x72;
+  static final LETTER_T = 0x74;
+  static final LETTER_U = 0x75;
+  static final LETTER_V = 0x76;
+  static final LETTER_X = 0x78;
+
+  static final LETTER_CAP_A = 0x41;
+  static final LETTER_CAP_F = 0x46;
+  static final LETTER_CAP_L = 0x4C;
+  static final LETTER_CAP_N = 0x4E;
+  static final LETTER_CAP_P = 0x50;
+  static final LETTER_CAP_U = 0x55;
+  static final LETTER_CAP_X = 0x58;
+
   static final C_SEQUENCE_ENTRY = 4;
   static final C_MAPPING_KEY = 5;
   static final C_MAPPING_VALUE = 6;
   static final C_COLLECT_ENTRY = 7;
   static final C_SEQUENCE_START = 8;
   static final C_SEQUENCE_END = 9;
   static final C_MAPPING_START = 10;
   static final C_MAPPING_END = 11;
   static final C_COMMENT = 12;
   static final C_ANCHOR = 13;
   static final C_ALIAS = 14;
   static final C_TAG = 15;
   static final C_LITERAL = 16;
   static final C_FOLDED = 17;
   static final C_SINGLE_QUOTE = 18;
   static final C_DOUBLE_QUOTE = 19;
   static final C_DIRECTIVE = 20;
   static final C_RESERVED = 21;
 
   static final BLOCK_OUT = 0;
   static final BLOCK_IN = 1;
   static final FLOW_OUT = 2;
   static final FLOW_IN = 3;
   static final BLOCK_KEY = 4;
   static final FLOW_KEY = 5;
 
+  static final CHOMPING_STRIP = 0;
+  static final CHOMPING_KEEP = 1;
+  static final CHOMPING_CLIP = 2;
+
   /** The source string being parsed. */
   final String s;
 
   /** The current position in the source string. */
   int pos = 0;
 
   /** The length of the string being parsed. */
   final int len;
 
   /** The current (0-based) line in the source string. */
@@ skipping 22 matching lines @@
 
   /**
    * The name of the context of the farthest position that has been parsed
    * successfully before backtracking. Used for error reporting.
    */
   String farthestContext = "document";
 
   /** A stack of the names of parse contexts. Used for error reporting. */
   List<String> contextStack;
 
+  /**
+   * The buffer containing string currently being captured.

[Bob Nystrom, 2012/05/18 21:06:30]

"string" -> "the string"

[nweiz, 2012/05/18 21:47:04]

Done.

+   */
+  StringBuffer capturedString;
+
+  /**
+   * The beginning of the current section of the captured string.
+   */
+  int captureStart;
+
+  /**
+   * Whether the current string capture is being overridden.
+   */
+  bool capturingAs = false;
+
   _Parser(String s)
     : this.s = s,
       len = s.length,
       contextStack = <String>["document"];
 
   /**
    * Return the character at the current position, then move that position
    * forward one character. Also updates the current line and column numbers.
    */
   int next() {
@@ skipping 42 matching lines @@
    */
   bool consume(bool matcher(int)) {
     if (matcher(peek())) {
       next();
       return true;
     }
     return false;
   }
 
   /**
+   * Consumes the current character if it equals [char].
+   */
+  bool consumeChar(int char) => consume((c) => c == char);
+
+  /**
    * Calls [consumer] until it returns a falsey value. Returns a list of all
    * truthy return values of [consumer], or null if it didn't consume anything.
    *
    * Conceptually, repeats a production one or more times.
    */
   List oneOrMore(consumer()) {
     var first = consumer();
     if (!truth(first)) return null;
     var out = [first];
     while (true) {
@@ skipping 37 matching lines @@
       if (truth(res)) return res;
     }
     return null;
   }
 
   /**
    * Calls [consumer] and returns its result, but rolls back the parser state if
    * [consumer] returns a falsey value.
    */
   transaction(consumer()) {
-    int oldPos = pos, oldLine = line, oldColumn = column;
+    int oldPos = pos, oldLine = line, oldColumn = column,
+      oldCaptureStart = captureStart;

[Bob Nystrom, 2012/05/18 21:06:30]

How about splitting these into separate declarations? Using "," seems a bit
gratuitous.

[nweiz, 2012/05/18 21:47:04]

Done.

+    String capturedSoFar = capturedString == null ? null :
+      capturedString.toString();
     var res = consumer();
     if (truth(res)) return res;
 
     pos = oldPos;
     line = oldLine;
     column = oldColumn;
+    captureStart = oldCaptureStart;
+    capturedString = capturedSoFar == null ? null :
+      new StringBuffer(capturedSoFar);
     return res;
   }
 
   /**
    * Consumes [n] characters matching [matcher], or none if there isn't a
    * complete match. The first argument to [matcher] is the character code, the
    * second is the index (from 0 to [n] - 1).
    *
    * Returns whether or not the characters were consumed.
    */
@@ skipping 18 matching lines @@
    */
   String stringOf(bool matcher(int)) =>
     captureString(() => oneOrMore(() => consume(matcher)));
 
   /**
    * Calls [consumer] and returns the string that was consumed while doing so,
    * or null if [consumer] returned a falsey value. Automatically wraps
    * [consumer] in `transaction`.
    */
   String captureString(consumer()) {
-    int start = pos;
+    if (capturedString != null) throw 'captureString calls may not be nested';

[Bob Nystrom, 2012/05/18 21:06:30]

This is a programmatic error, right? If so, I would use assert().

[nweiz, 2012/05/18 21:47:04]

Done.

+
+    captureStart = pos;
+    capturedString = new StringBuffer();
     var res = transaction(consumer);
-    if (!truth(res)) return null;
-    return s.substring(start, pos);
+    if (!truth(res)) {
+      captureStart = capturedString = null;

[Bob Nystrom, 2012/05/18 21:06:30]

This chained assignment doesn't really add a lot of value and might cause a
static type warning. Split into separate assignments?

[nweiz, 2012/05/18 21:47:04]

Done.

+      return null;
+    }
+
+    flushCapture();
+    var result = capturedString.toString();
+    captureStart = capturedString = null;

[Bob Nystrom, 2012/05/18 21:06:30]

Ditto.

[nweiz, 2012/05/18 21:47:04]

Done.

+    return result;
+  }
+
+  captureAs(String replacement, consumer()) =>
+    captureAndTransform(consumer, (_) => replacement);

[Bob Nystrom, 2012/05/18 21:06:30]

+2 indent.

[nweiz, 2012/05/18 21:47:04]

Done.

+
+  captureAndTransform(consumer(), String transformation(String captured)) {
+    if (capturedString == null) return consumer();
+    if (capturingAs) return consumer();
+
+    flushCapture();
+    capturingAs = true;
+    var res = consumer();
+    capturingAs = false;
+    if (!truth(res)) return res;
+
+    capturedString.add(transformation(s.substring(captureStart, pos)));
+    captureStart = pos;
+    return res;
+  }
+
+  void flushCapture() {
+    capturedString.add(s.substring(captureStart, pos));
+    captureStart = pos;
   }
 
   /**
    * Adds a tag and an anchor to [node], if they're defined.
    */
   _Node addProps(_Node node, _Pair<_Tag, String> props) {
+    if (props == null || node == null) return node;
     if (truth(props.first)) node.tag = props.first;
     if (truth(props.last)) node.anchor = props.last;
     return node;
   }
 
   /** Creates a MappingNode from [pairs]. */
   _MappingNode map(List<_Pair<_Node, _Node>> pairs) {
     var content = new Map<_Node, _Node>();
     pairs.forEach((pair) => content[pair.first] = pair.last);
     return new _MappingNode("?", content);
@@ skipping 35 matching lines @@
         "invalid YAML in $farthestContext");
   }
 
   /** Returns the number of spaces after the current position. */ 
   int countIndentation() {
     var i = 0;
     while (peek(i) == SP) i++;
     return i;
   }
 
+  /** Returns the indentation for a block scalar. */
+  int blockScalarAdditionalIndentation(_BlockHeader header, int indent) {
+    if (!header.autoDetectIndent) return header.additionalIndent;
+
+    var maxSpaces = 0;
+    var maxSpacesLine = 0;
+    var spaces = 0;
+    transaction(() {
+      do {
+        spaces = captureString(() => zeroOrMore(() => consumeChar(SP))).length;
+        if (spaces > maxSpaces) {
+          maxSpaces = spaces;
+          maxSpacesLine = line;
+        }
+      } while (b_break());
+      return false;
+    });
+
+    // If the next non-empty line isn't indented further than the start of the
+    // block scalar, that means the scalar is going to be empty. Returning any
+    // value > 0 will cause the parser not to consume any text.
+    if (spaces <= indent) return 1;
+
+    // It's an error for a leading empty line to be indented more than the first
+    // non-empty line.
+    if (maxSpaces > spaces) {
+      throw new SyntaxError(maxSpacesLine + 1, maxSpaces,
+          "leading empty lines may not be indented more than the first "

[Bob Nystrom, 2012/05/18 21:06:30]

Sentence case and ".".

[nweiz, 2012/05/18 21:47:04]

Done.

+          "non-empty line");
+    }
+
+    return spaces - indent;
+  }
+
   /** Returns whether the current position is at the beginning of a line. */
   bool get atStartOfLine() => column == 0;
 
   /** Returns whether the current position is at the end of the input. */
   bool get atEndOfFile() => pos == len;
 
   /**
    * Given an indicator character, returns the type of that indicator (or null
    * if the indicator isn't found.
    */
@@ skipping 28 matching lines @@
     return char == TAB ||
       char == LF ||
       char == CR ||
       (char >= SP && char <= TILDE) ||
       char == NEL ||
       (char >= 0xA0 && char <= 0xD7FF) ||
       (char >= 0xE000 && char <= 0xFFFD) ||
       (char >= 0x10000 && char <= 0x10FFFF);
   }
 
+  // 2
+  bool isJson(int char) => char == TAB || (char >= SP && char <= 0x10FFFF);
+
   // 22
   bool c_indicator(int type) => consume((c) => indicatorType(c) == type);
 
   // 23
   bool isFlowIndicator(int char) {
     var indicator = indicatorType(char);
     return indicator == C_COLLECT_ENTRY ||
       indicator == C_SEQUENCE_START ||
       indicator == C_SEQUENCE_END ||
       indicator == C_MAPPING_START ||
       indicator == C_MAPPING_END;
   }
 
   // 26
   bool isBreak(int char) => char == LF || char == CR;
 
   // 27
   bool isNonBreak(int char) => isPrintable(char) && !isBreak(char);
 
+  // 28
+  bool b_break() {
+    if (consumeChar(CR)) {
+      zeroOrOne(() => consumeChar(LF));
+      return true;
+    }
+    return consumeChar(LF);
+  }
+
+  // 29
+  bool b_asLineFeed() => captureAs("\n", () => b_break());
+
   // 30
-  bool b_non_content() => consume(isBreak);
+  bool b_nonContent() => captureAs("", () => b_break());
 
   // 33
   bool isSpace(int char) => char == SP || char == TAB;
 
   // 34
   bool isNonSpace(int char) => isNonBreak(char) && !isSpace(char);
 
+  // 35
+  bool isDecDigit(int char) => char >= NUMBER_0 && char <= NUMBER_9;
+
+  // 36
+  bool isHexDigit(int char) {
+    return isDecDigit(char) ||
+      (char >= LETTER_A && char <= LETTER_F) ||
+      (char >= LETTER_CAP_A && char <= LETTER_CAP_F);
+  }
+
+  // 41
+  bool c_escape() => captureAs("", () => consumeChar(BACKSLASH));
+
+  // 42
+  bool ns_escNull() => captureAs("\x00", () => consumeChar(NUMBER_0));
+
+  // 43
+  bool ns_escBell() => captureAs("\x07", () => consumeChar(LETTER_A));
+
+  // 44
+  bool ns_escBackspace() => captureAs("\b", () => consumeChar(LETTER_B));
+
+  // 45
+  bool ns_escHorizontalTab() => captureAs("\t", () {
+    return consume((c) => c == LETTER_T || c == TAB);
+  });
+
+  // 46
+  bool ns_escLineFeed() => captureAs("\n", () => consumeChar(LETTER_N));
+
+  // 47
+  bool ns_escVerticalTab() => captureAs("\v", () => consumeChar(LETTER_V));
+
+  // 48
+  bool ns_escFormFeed() => captureAs("\f", () => consumeChar(LETTER_F));
+
+  // 49
+  bool ns_escCarriageReturn() => captureAs("\r", () => consumeChar(LETTER_R));
+
+  // 50
+  bool ns_escEscape() => captureAs("\x1B", () => consumeChar(LETTER_E));
+
+  // 51
+  bool ns_escSpace() => consumeChar(SP);
+
+  // 52
+  bool ns_escDoubleQuote() => consumeChar(DOUBLE_QUOTE);
+
+  // 53
+  bool ns_escSlash() => consumeChar(SLASH);
+
+  // 54
+  bool ns_escBackslash() => consumeChar(BACKSLASH);
+
+  // 55
+  bool ns_escNextLine() => captureAs("\x85", () => consumeChar(LETTER_CAP_N));
+
+  // 56
+  bool ns_escNonBreakingSpace() =>
+    captureAs("\xA0", () => consumeChar(UNDERSCORE));
+
+  // 57
+  bool ns_escLineSeparator() =>
+    captureAs("\u2028", () => consumeChar(LETTER_CAP_L));
+
+  // 58
+  bool ns_escParagraphSeparator() =>
+    captureAs("\u2029", () => consumeChar(LETTER_CAP_P));
+
+  // 59
+  bool ns_esc8Bit() => ns_escNBit(LETTER_X, 2);
+
+  // 60
+  bool ns_esc16Bit() => ns_escNBit(LETTER_U, 4);
+
+  // 61
+  bool ns_esc32Bit() => ns_escNBit(LETTER_CAP_U, 8);
+
+  // Helper method for 59 - 61
+  bool ns_escNBit(int char, int digits) {
+    if (!captureAs('', () => consumeChar(char))) return false;
+    var captured = captureAndTransform(
+        () => nAtOnce(digits, (c, _) => isHexDigit(c)),
+        (hex) => new String.fromCharCodes([Math.parseInt("0x$hex")]));
+    return expect(captured, "$digits hexidecimal digits");
+  }
+
+  // 62
+  bool c_ns_escChar() => context('escape sequence', () => transaction(() {
+      if (!truth(c_escape())) return false;
+      return truth(or([
+        ns_escNull, ns_escBell, ns_escBackspace, ns_escHorizontalTab,
+        ns_escLineFeed, ns_escVerticalTab, ns_escFormFeed, ns_escCarriageReturn,
+        ns_escEscape, ns_escSpace, ns_escDoubleQuote, ns_escSlash,
+        ns_escBackslash, ns_escNextLine, ns_escNonBreakingSpace,
+        ns_escLineSeparator, ns_escParagraphSeparator, ns_esc8Bit, ns_esc16Bit,
+        ns_esc32Bit
+      ]));
+    }));
+
   // 63
   bool s_indent(int indent) => nAtOnce(indent, (c, i) => c == SP);
 
-  // 66
-  bool s_separateInLine() => transaction(() =>
-    truth(oneOrMore(() => consume(isSpace))) || atStartOfLine);
-
-  // 69
-  bool s_flowLinePrefix(int indent) {
-    if (!s_indent(indent)) return false;
-    zeroOrOne(s_separateInLine);
+  // 64
+  bool s_indentLessThan(int indent) {
+    for (int i = 0; i < indent - 1; i++) {
+      if (!consumeChar(SP)) break;
+    }
     return true;
   }
 
+  // 65
+  bool s_indentLessThanOrEqualTo(int indent) => s_indentLessThan(indent + 1);
+
+  // 66
+  bool s_separateInLine() => transaction(() {
+    return captureAs('', () =>
+        truth(oneOrMore(() => consume(isSpace))) || atStartOfLine);
+  });
+
+  // 67
+  bool s_linePrefix(int indent, int ctx) => captureAs("", () {
+    switch (ctx) {
+    case BLOCK_OUT:
+    case BLOCK_IN:
+      return s_blockLinePrefix(indent);
+    case FLOW_OUT:
+    case FLOW_IN:
+      return s_flowLinePrefix(indent);
+    }
+  });
+
+  // 68
+  bool s_blockLinePrefix(int indent) => s_indent(indent);
+
+  // 69
+  bool s_flowLinePrefix(int indent) => captureAs('', () {
+    if (!truth(s_indent(indent))) return false;
+    zeroOrOne(s_separateInLine);
+    return true;
+  });
+
+  // 70
+  bool l_empty(int indent, int ctx) => transaction(() {
+    var start = or([
+      () => s_linePrefix(indent, ctx),
+      () => s_indentLessThan(indent)
+    ]);
+    if (!truth(start)) return false;
+    return b_asLineFeed();
+  });
+
+  // 71
+  bool b_asSpace() => captureAs(" ", () => consume(isBreak));
+
+  // 72
+  bool b_l_trimmed(int indent, int ctx) => transaction(() {
+    if (!truth(b_nonContent())) return false;
+    return truth(oneOrMore(() => captureAs("\n", () => l_empty(indent, ctx))));
+  });
+
+  // 73
+  bool b_l_folded(int indent, int ctx) =>
+    or([() => b_l_trimmed(indent, ctx), b_asSpace]);
+
   // 74
-  bool s_flowFolded(int indent) => false; // TODO(nweiz): implement
+  bool s_flowFolded(int indent) => transaction(() {
+    zeroOrOne(s_separateInLine);
+    if (!truth(b_l_folded(indent, FLOW_IN))) return false;
+    return s_flowLinePrefix(indent);
+  });
 
   // 75
   bool c_nb_commentText() {
-    if (!c_indicator(C_COMMENT)) return false;
+    if (!truth(c_indicator(C_COMMENT))) return false;
     zeroOrMore(() => consume(isNonBreak));
     return true;
   }
 
   // 76
-  bool b_comment() => atEndOfFile || b_non_content();
+  bool b_comment() => atEndOfFile || b_nonContent();
 
   // 77
   bool s_b_comment() {
-    if (s_separateInLine()) {
+    if (truth(s_separateInLine())) {
       zeroOrOne(c_nb_commentText);
     }
     return b_comment();
   }
 
   // 78
   bool l_comment() => transaction(() {
-    if (!s_separateInLine()) return false;
+    if (!truth(s_separateInLine())) return false;
     zeroOrOne(c_nb_commentText);
     return b_comment();
   });
 
   // 79
   bool s_l_comments() {
-    if (!s_b_comment() && !atStartOfLine) return false;
+    if (!truth(s_b_comment()) && !atStartOfLine) return false;
     zeroOrMore(l_comment);
     return true;
   }
 
   // 80
   bool s_separate(int indent, int ctx) {
     switch (ctx) {
     case BLOCK_OUT:
     case BLOCK_IN:
     case FLOW_OUT:
@@ skipping 14 matching lines @@
 
   // 82
   bool l_directive() => false; // TODO(nweiz): implement
 
   // 96
   _Pair<_Tag, String> c_ns_properties(int indent, int ctx) {
     var tag, anchor;
     tag = c_ns_tagProperty();
     if (truth(tag)) {
       anchor = transaction(() {
-        if (!s_separate(indent, ctx)) return null;
+        if (!truth(s_separate(indent, ctx))) return null;
         return c_ns_anchorProperty();
       });
       return new _Pair<_Tag, String>(tag, anchor);
     }
 
     anchor = c_ns_anchorProperty();
     if (truth(anchor)) {
       tag = transaction(() {
-        if (!s_separate(indent, ctx)) return null;
+        if (!truth(s_separate(indent, ctx))) return null;
         return c_ns_tagProperty();
       });
       return new _Pair<_Tag, String>(tag, anchor);
     }
 
     return null;
   }
 
   // 97
   _Tag c_ns_tagProperty() => null; // TODO(nweiz): implement
 
   // 101
   String c_ns_anchorProperty() => null; // TODO(nweiz): implement
 
   // 102
   bool isAnchorChar(int char) => isNonSpace(char) && !isFlowIndicator(char);
 
   // 103
   String ns_anchorName() =>
     captureString(() => oneOrMore(() => consume(isAnchorChar)));
 
   // 104
   _Node c_ns_aliasNode() {
-    if (!c_indicator(C_ALIAS)) return null;
+    if (!truth(c_indicator(C_ALIAS))) return null;
     var name = expect(ns_anchorName(), 'anchor name');
     return new _AliasNode(name);
   }
 
   // 105
   _ScalarNode e_scalar() => new _ScalarNode("?", content: "");
 
   // 106
   _ScalarNode e_node() => e_scalar();
 
+  // 107
+  bool nb_doubleChar() => or([
+    c_ns_escChar,
+    () => consume((c) => isJson(c) && c != BACKSLASH && c != DOUBLE_QUOTE)
+  ]);
+
+  // 108
+  bool ns_doubleChar() => !isSpace(peek()) && truth(nb_doubleChar());
+
+  // 109
+  _Node c_doubleQuoted(int indent, int ctx) => context('string', () {
+    return transaction(() {
+      if (!truth(c_indicator(C_DOUBLE_QUOTE))) return null;
+      var contents = nb_doubleText(indent, ctx);
+      if (!truth(c_indicator(C_DOUBLE_QUOTE))) return null;
+      return new _ScalarNode("!", contents);
+    });
+  });
+
+  // 110
+  String nb_doubleText(int indent, int ctx) => captureString(() {
+    switch (ctx) {
+    case FLOW_OUT:
+    case FLOW_IN:
+      nb_doubleMultiLine(indent);
+      break;
+    case BLOCK_KEY:
+    case FLOW_KEY:
+      nb_doubleOneLine();
+      break;
+    }
+    return true;
+  });
+
+  // 111
+  void nb_doubleOneLine() {
+    zeroOrMore(nb_doubleChar);
+  }
+
+  // 112
+  bool s_doubleEscaped(int indent) => transaction(() {
+    zeroOrMore(() => consume(isSpace));
+    if (!captureAs("", () => consumeChar(BACKSLASH))) return false;
+    if (!truth(b_nonContent())) return false;
+    zeroOrMore(() => captureAs("\n", () => l_empty(indent, FLOW_IN)));
+    return s_flowLinePrefix(indent);
+  });
+
+  // 113
+  bool s_doubleBreak(int indent) => or([
+    () => s_doubleEscaped(indent),
+    () => s_flowFolded(indent)
+  ]);
+
+  // 114
+  void nb_ns_doubleInLine() {
+    zeroOrMore(() => transaction(() {
+        zeroOrMore(() => consume(isSpace));
+        return ns_doubleChar();
+      }));
+  }
+
+  // 115
+  bool s_doubleNextLine(int indent) {
+    if (!truth(s_doubleBreak(indent))) return false;
+    zeroOrOne(() {
+      if (!truth(ns_doubleChar())) return;
+      nb_ns_doubleInLine();
+      or([
+        () => s_doubleNextLine(indent),
+        () => zeroOrMore(() => consume(isSpace))
+      ]);
+    });
+    return true;
+  }
+
+  // 116
+  void nb_doubleMultiLine(int indent) {
+    nb_ns_doubleInLine();
+    or([
+      () => s_doubleNextLine(indent),
+      () => zeroOrMore(() => consume(isSpace))
+    ]);
+  }
+
+  // 117
+  bool c_quotedQuote() => captureAs("'", () => rawString("''"));
+
+  // 118
+  bool nb_singleChar() => or([
+    c_quotedQuote,
+    () => consume((c) => isJson(c) && c != SINGLE_QUOTE)
+  ]);
+
+  // 119
+  bool ns_singleChar() => !isSpace(peek()) && truth(nb_singleChar());
+
+  // 120
+  _Node c_singleQuoted(int indent, int ctx) => context('string', () {
+    return transaction(() {
+      if (!truth(c_indicator(C_SINGLE_QUOTE))) return null;
+      var contents = nb_singleText(indent, ctx);
+      if (!truth(c_indicator(C_SINGLE_QUOTE))) return null;
+      return new _ScalarNode("!", contents);
+    });
+  });
+
+  // 121
+  String nb_singleText(int indent, int ctx) => captureString(() {
+    switch (ctx) {
+    case FLOW_OUT:
+    case FLOW_IN:
+      nb_singleMultiLine(indent);
+      break;
+    case BLOCK_KEY:
+    case FLOW_KEY:
+      nb_singleOneLine(indent);
+      break;
+    }
+    return true;
+  });
+
+  // 122
+  void nb_singleOneLine(int indent) {
+    zeroOrMore(nb_singleChar);
+  }
+
+  // 123
+  void nb_ns_singleInLine() {
+    zeroOrMore(() => transaction(() {
+      zeroOrMore(() => consume(isSpace));
+      return ns_singleChar();
+    }));
+  }
+
+  // 124
+  bool s_singleNextLine(int indent) {
+    if (!truth(s_flowFolded(indent))) return false;
+    zeroOrOne(() {
+      if (!truth(ns_singleChar())) return;
+      nb_ns_singleInLine();
+      or([
+        () => s_singleNextLine(indent),
+        () => zeroOrMore(() => consume(isSpace))
+      ]);
+    });
+    return true;
+  }
+
+  // 125
+  void nb_singleMultiLine(int indent) {
+    nb_ns_singleInLine();
+    or([
+      () => s_singleNextLine(indent),
+      () => zeroOrMore(() => consume(isSpace))
+    ]);
+  }
+
   // 126
   bool ns_plainFirst(int ctx) {
     var char = peek();
     var indicator = indicatorType(char);
     if (indicator == C_RESERVED) {
       error("reserved indicators can't start a plain scalar");
     }
     var match = (isNonSpace(char) && indicator == null) ||
       ((indicator == C_MAPPING_KEY ||
         indicator == C_MAPPING_VALUE ||
@@ skipping 29 matching lines @@
     var nonMappingColon = indicator == C_MAPPING_VALUE &&
       isPlainSafe(ctx, peek(1));
     var match = safeChar || nonCommentHash || nonMappingColon;
 
     if (match) next();
     return match;
   }
 
   // 131
   String ns_plain(int indent, int ctx) => context('plain scalar', () {
-    switch (ctx) {
-    case FLOW_OUT:
-    case FLOW_IN:
-      return ns_plainMultiLine(indent, ctx);
-    case BLOCK_KEY:
-    case FLOW_KEY:
-      return ns_plainOneLine(ctx);
-    default: throw 'invalid context "$ctx"';
-    }
+    return captureString(() {
+      switch (ctx) {
+      case FLOW_OUT:
+      case FLOW_IN:
+        return ns_plainMultiLine(indent, ctx);
+      case BLOCK_KEY:
+      case FLOW_KEY:
+        return ns_plainOneLine(ctx);
+      default: throw 'invalid context "$ctx"';
+      }
+    });
   });
 
   // 132
   void nb_ns_plainInLine(int ctx) {
     zeroOrMore(() => transaction(() {
       zeroOrMore(() => consume(isSpace));
       return ns_plainChar(ctx);
     }));
   }
 
   // 133
-  String ns_plainOneLine(int ctx) => captureString(() {
-    if (c_forbidden()) return false;
-    if (!ns_plainFirst(ctx)) return false;
+  bool ns_plainOneLine(int ctx) {
+    if (truth(c_forbidden())) return false;
+    if (!truth(ns_plainFirst(ctx))) return false;
+    nb_ns_plainInLine(ctx);
+    return true;
+  }
+
+  // 134
+  bool s_ns_plainNextLine(int indent, int ctx) => transaction(() {
+    if (!truth(s_flowFolded(indent))) return false;
+    if (truth(c_forbidden())) return false;
+    if (!truth(ns_plainChar(ctx))) return false;
     nb_ns_plainInLine(ctx);
     return true;
   });
 
-  // 134
-  bool s_ns_plainNextLine(int indent, int ctx) => transaction(() {
-    if (c_forbidden()) return false;
-    if (!s_flowFolded(indent)) return false;
-    if (!ns_plainChar(ctx)) return false;
-    nb_ns_plainInLine(ctx);
-    return true;
-  });
-
   // 135
-  String ns_plainMultiLine(int indent, int ctx) => captureString(() {
+  bool ns_plainMultiLine(int indent, int ctx) {
     if (!truth(ns_plainOneLine(ctx))) return false;
     zeroOrMore(() => s_ns_plainNextLine(indent, ctx));
     return true;
+  }
+
+  // 136
+  int inFlow(int ctx) {
+    switch (ctx) {
+    case FLOW_OUT:
+    case FLOW_IN:
+      return FLOW_IN;
+    case BLOCK_KEY:
+    case FLOW_KEY:
+      return FLOW_KEY;
+    }
+  }
+
+  // 137
+  _SequenceNode c_flowSequence(int indent, int ctx) => transaction(() {
+    if (!truth(c_indicator(C_SEQUENCE_START))) return null;
+    zeroOrOne(() => s_separate(indent, ctx));
+    var content = zeroOrOne(() => ns_s_flowSeqEntries(indent, inFlow(ctx)));
+    if (!truth(c_indicator(C_SEQUENCE_END))) return null;
+    return new _SequenceNode("?", new List<_Node>.from(content));
   });
 
+  // 138
+  Collection<_Node> ns_s_flowSeqEntries(int indent, int ctx) {
+    var first = ns_flowSeqEntry(indent, ctx);
+    if (!truth(first)) return new Queue<_Node>();
+    zeroOrOne(() => s_separate(indent, ctx));
+
+    var rest;
+    if (truth(c_indicator(C_COLLECT_ENTRY))) {
+      zeroOrOne(() => s_separate(indent, ctx));
+      rest = zeroOrOne(() => ns_s_flowSeqEntries(indent, ctx));
+    }
+
+    if (rest == null) rest = new Queue<_Node>();
+    rest.addFirst(first);
+
+    return rest;
+  }
+
+  // 139
+  _Node ns_flowSeqEntry(int indent, int ctx) => or([
+    () => ns_flowPair(indent, ctx),
+    () => ns_flowNode(indent, ctx)
+  ]);
+
+  // 140
+  _Node c_flowMapping(int indent, int ctx) {
+    if (!truth(c_indicator(C_MAPPING_START))) return null;
+    zeroOrOne(() => s_separate(indent, ctx));
+    var content = zeroOrOne(() => ns_s_flowMapEntries(indent, inFlow(ctx)));
+    if (!truth(c_indicator(C_MAPPING_END))) return null;
+    return new _MappingNode("?", content);
+  }
+
+  // 141
+  YamlMap ns_s_flowMapEntries(int indent, int ctx) {
+    var first = ns_flowMapEntry(indent, ctx);
+    if (!truth(first)) return new YamlMap();
+    zeroOrOne(() => s_separate(indent, ctx));
+
+    var rest;
+    if (truth(c_indicator(C_COLLECT_ENTRY))) {
+      zeroOrOne(() => s_separate(indent, ctx));
+      rest = ns_s_flowMapEntries(indent, ctx);
+    }
+
+    if (rest == null) rest = new YamlMap();
+
+    // TODO(nweiz): Duplicate keys should be an error. This includes keys with
+    // different representations but the same value (e.g. 10 vs 0xa). To make
+    // this user-friendly we'll probably also want to associate nodes with a
+    // source range.
+    if (!rest.containsKey(first.first)) rest[first.first] = first.last;
+
+    return rest;
+  }
+
+  // 142
+  _Pair<_Node, _Node> ns_flowMapEntry(int indent, int ctx) => or([
+    () => transaction(() {
+      if (!truth(c_indicator(C_MAPPING_KEY))) return false;
+      if (!truth(s_separate(indent, ctx))) return false;
+      return ns_flowMapExplicitEntry(indent, ctx);
+    }),
+    () => ns_flowMapImplicitEntry(indent, ctx)
+  ]);
+
+  // 143
+  _Pair<_Node, _Node> ns_flowMapExplicitEntry(int indent, int ctx) => or([
+    () => ns_flowMapImplicitEntry(indent, ctx),
+    () => new _Pair<_Node, _Node>(e_node(), e_node())
+  ]);
+
+  // 144
+  _Pair<_Node, _Node> ns_flowMapImplicitEntry(int indent, int ctx) => or([
+    () => ns_flowMapYamlKeyEntry(indent, ctx),
+    () => c_ns_flowMapEmptyKeyEntry(indent, ctx),
+    () => c_ns_flowMapJsonKeyEntry(indent, ctx)
+  ]);
+
+  // 145
+  _Pair<_Node, _Node> ns_flowMapYamlKeyEntry(int indent, int ctx) {
+    var key = ns_flowYamlNode(indent, ctx);
+    if (!truth(key)) return null;
+    var value = or([
+      () => transaction(() {
+        zeroOrOne(() => s_separate(indent, ctx));
+        return c_ns_flowMapSeparateValue(indent, ctx);
+      }),
+      e_node
+    ]);
+    return new _Pair<_Node, _Node>(key, value);
+  }
+
+  // 146
+  _Pair<_Node, _Node> c_ns_flowMapEmptyKeyEntry(int indent, int ctx) {
+    var value = c_ns_flowMapSeparateValue(indent, ctx);
+    if (!truth(value)) return null;
+    return new _Pair<_Node, _Node>(e_node(), value);
+  }
+
+  // 147
+  _Node c_ns_flowMapSeparateValue(int indent, int ctx) => transaction(() {
+    if (!truth(c_indicator(C_MAPPING_VALUE))) return null;
+    if (isPlainSafe(ctx, peek())) return null;
+
+    return or([
+      () => transaction(() {
+        if (!s_separate(indent, ctx)) return null;
+        return ns_flowNode(indent, ctx);
+      }),
+      e_node
+    ]);
+  });
+
+  // 148
+  _Pair<_Node, _Node> c_ns_flowMapJsonKeyEntry(int indent, int ctx) {
+    var key = c_flowJsonNode(indent, ctx);
+    if (!truth(key)) return null;
+    var value = or([
+      () => transaction(() {
+        zeroOrOne(() => s_separate(indent, ctx));
+        return c_ns_flowMapAdjacentValue(indent, ctx);
+      }),
+      e_node
+    ]);
+    return new _Pair<_Node, _Node>(key, value);
+  }
+
+  // 149
+  _Node c_ns_flowMapAdjacentValue(int indent, int ctx) {
+    if (!truth(c_indicator(C_MAPPING_VALUE))) return null;
+    return or([
+      () => transaction(() {
+        zeroOrOne(() => s_separate(indent, ctx));
+        return ns_flowNode(indent, ctx);
+      }),
+      e_node
+    ]);
+  }
+
+  // 150
+  _Node ns_flowPair(int indent, int ctx) {
+    var pair = or([
+      () => transaction(() {
+        if (!truth(c_indicator(C_MAPPING_KEY))) return null;
+        if (!truth(s_separate(indent, ctx))) return null;
+        return ns_flowMapExplicitEntry(indent, ctx);
+      }),
+      () => ns_flowPairEntry(indent, ctx)
+    ]);
+    if (!truth(pair)) return null;
+
+    return map([pair]);
+  }
+
+  // 151
+  _Pair<_Node, _Node> ns_flowPairEntry(int indent, int ctx) => or([
+    () => ns_flowPairYamlKeyEntry(indent, ctx),
+    () => c_ns_flowMapEmptyKeyEntry(indent, ctx),
+    () => c_ns_flowPairJsonKeyEntry(indent, ctx)
+  ]);
+
+  // 152
+  _Pair<_Node, _Node> ns_flowPairYamlKeyEntry(int indent, int ctx) =>
+    transaction(() {
+      var key = ns_s_implicitYamlKey(FLOW_KEY);
+      if (!truth(key)) return null;
+      var value = c_ns_flowMapSeparateValue(indent, ctx);
+      if (!truth(value)) return null;
+      return new _Pair<_Node, _Node>(key, value);
+    });
+
+  // 153
+  _Pair<_Node, _Node> c_ns_flowPairJsonKeyEntry(int indent, int ctx) =>
+    transaction(() {
+      var key = c_s_implicitJsonKey(FLOW_KEY);
+      if (!truth(key)) return null;
+      var value = c_ns_flowMapAdjacentValue(indent, ctx);
+      if (!truth(value)) return null;
+      return new _Pair<_Node, _Node>(key, value);
+    });
+
   // 154
-  _Node c_s_implicitYamlKey(int ctx) => transaction(() {
+  _Node ns_s_implicitYamlKey(int ctx) => transaction(() {
+    // TODO(nweiz): this is supposed to be limited to 1024 characters.
+
     // The indentation parameter is "null" since it's unused in this path
     var node = ns_flowYamlNode(null, ctx);
     if (!truth(node)) return null;
     zeroOrOne(s_separateInLine);
     return node;
   });
 
   // 155
-  _Node c_s_implicitJsonKey(int ctx) => null; // TODO(nweiz): implement
+  _Node c_s_implicitJsonKey(int ctx) => transaction(() {
+    // TODO(nweiz): this is supposed to be limited to 1024 characters.
+
+    // The indentation parameter is "null" since it's unused in this path
+    var node = c_flowJsonNode(null, ctx);
+    if (!truth(node)) return null;
+    zeroOrOne(s_separateInLine);
+    return node;
+  });
 
   // 156
   _Node ns_flowYamlContent(int indent, int ctx) {
     var str = ns_plain(indent, ctx);
     if (!truth(str)) return null;
     return new _ScalarNode("?", content: str);
   }
 
   // 157
-  // TODO(nweiz): implement
-  _Node ns_flowJsonContent(int indent, int ctx) => null;
+  _Node c_flowJsonContent(int indent, int ctx) => or([
+    () => c_flowSequence(indent, ctx),
+    () => c_flowMapping(indent, ctx),
+    () => c_singleQuoted(indent, ctx),
+    () => c_doubleQuoted(indent, ctx)
+  ]);
 
   // 158
   _Node ns_flowContent(int indent, int ctx) => or([
     () => ns_flowYamlContent(indent, ctx),
-    () => ns_flowJsonContent(indent, ctx)
+    () => c_flowJsonContent(indent, ctx)
   ]);
 
   // 159
   _Node ns_flowYamlNode(int indent, int ctx) => or([
     c_ns_aliasNode,
     () => ns_flowYamlContent(indent, ctx),
     () {
       var props = c_ns_properties(indent, ctx);
       if (!truth(props)) return null;
       var node = or([
         () => transaction(() {
-          if (!s_separate(indent, ctx)) return null;
+          if (!truth(s_separate(indent, ctx))) return null;
           return ns_flowYamlContent(indent, ctx);
         }),
         e_scalar
       ]);
       return addProps(node, props);
     }
   ]);
 
+  // 160
+  _Node c_flowJsonNode(int indent, int ctx) => transaction(() {
+    var props;
+    zeroOrOne(() => transaction(() {
+        props = c_ns_properties(indent, ctx);
+        if (!truth(props)) return null;
+        return s_separate(indent, ctx);
+      }));
+
+    return addProps(c_flowJsonContent(indent, ctx), props);
+  });
+
   // 161
   _Node ns_flowNode(int indent, int ctx) => or([
     c_ns_aliasNode,
     () => ns_flowContent(indent, ctx),
     () => transaction(() {
       var props = c_ns_properties(indent, ctx);
       if (!truth(props)) return null;
       var node = or([
         () => transaction(() => s_separate(indent, ctx) ?
             ns_flowContent(indent, ctx) : null),
         e_scalar]);
       return addProps(node, props);
     })
   ]);
 
+  // 162
+  _BlockHeader c_b_blockHeader() => transaction(() {
+    var indentation = c_indentationIndicator();
+    var chomping = c_chompingIndicator();
+    if (!truth(indentation)) indentation = c_indentationIndicator();
+    if (!truth(s_b_comment())) return null;
+
+    return new _BlockHeader(indentation, chomping);
+  });
+
+  // 163
+  int c_indentationIndicator() {
+    if (!isDecDigit(peek())) return null;
+    return next() - NUMBER_0;
+  }
+
+  // 164
+  int c_chompingIndicator() {
+    switch (peek()) {
+    case HYPHEN:
+      next();
+      return CHOMPING_STRIP;
+    case PLUS:
+      next();
+      return CHOMPING_KEEP;
+    default:
+      return CHOMPING_CLIP;
+    }
+  }
+
+  // 165
+  bool b_chompedLast(int chomping) {
+    if (atEndOfFile) return true;
+    switch (chomping) {
+    case CHOMPING_STRIP:
+      return b_nonContent();
+    case CHOMPING_CLIP:
+    case CHOMPING_KEEP:
+      return b_asLineFeed();
+    }
+  }
+
+  // 166
+  void l_chompedEmpty(int indent, int chomping) {
+    switch (chomping) {
+    case CHOMPING_STRIP:
+    case CHOMPING_CLIP:
+      l_stripEmpty(indent);
+      break;
+    case CHOMPING_KEEP:
+      l_keepEmpty(indent);
+      break;
+    }
+  }
+
+  // 167
+  void l_stripEmpty(int indent) => captureAs('', () {
+    zeroOrMore(() => transaction(() {
+        if (!truth(s_indentLessThanOrEqualTo(indent))) return false;
+        return b_nonContent();
+      }));
+    zeroOrOne(() => l_trailComments(indent));
+    return true;
+  });
+
+  // 168
+  void l_keepEmpty(int indent) {
+    zeroOrMore(() => captureAs('\n', () => l_empty(indent, BLOCK_IN)));
+    zeroOrOne(() => captureAs('', () => l_trailComments(indent)));
+  }
+
+  // 169
+  bool l_trailComments(int indent) => transaction(() {
+    if (!truth(s_indentLessThanOrEqualTo(indent))) return false;
+    if (!truth(c_nb_commentText())) return false;
+    if (!truth(b_comment())) return false;
+    zeroOrMore(l_comment);
+    return true;
+  });
+
   // 170
-  _Node c_l_literal(int indent) => null; // TODO(nweiz); implement
+  _Node c_l_literal(int indent) => transaction(() {
+    if (!truth(c_indicator(C_LITERAL))) return null;
+    var header = c_b_blockHeader();
+    if (!truth(header)) return null;
+
+    var additionalIndent = blockScalarAdditionalIndentation(header, indent);
+    var content = l_literalContent(indent + additionalIndent, header.chomping);
+    if (!truth(content)) return null;
+
+    return new _ScalarNode("!", content);
+  });
+
+  // 171
+  bool l_nb_literalText(int indent) => transaction(() {
+    zeroOrMore(() => captureAs("\n", () => l_empty(indent, BLOCK_IN)));
+    if (!truth(captureAs("", () => s_indent(indent)))) return false;
+    return truth(oneOrMore(() => consume(isNonBreak)));
+  });
+
+  // 172
+  bool b_nb_literalNext(int indent) => transaction(() {
+    if (!truth(b_asLineFeed())) return false;
+    return l_nb_literalText(indent);
+  });
+
+  // 173
+  String l_literalContent(int indent, int chomping) => captureString(() {
+    transaction(() {
+      if (!truth(l_nb_literalText(indent))) return false;
+      zeroOrMore(() => b_nb_literalNext(indent));
+      return b_chompedLast(chomping);
+    });
+    l_chompedEmpty(indent, chomping);
+    return true;
+  });
 
   // 174
-  _Node c_l_folded(int indent) => null; // TODO(nweiz); implement
+  _Node c_l_folded(int indent) => transaction(() {
+    if (!truth(c_indicator(C_FOLDED))) return null;
+    var header = c_b_blockHeader();
+    if (!truth(header)) return null;
+
+    var additionalIndent = blockScalarAdditionalIndentation(header, indent);
+    var content = l_foldedContent(indent + additionalIndent, header.chomping);
+    if (!truth(content)) return null;
+
+    return new _ScalarNode("!", content);
+  });
+
+  // 175
+  bool s_nb_foldedText(int indent) => transaction(() {
+    if (!truth(captureAs('', () => s_indent(indent)))) return false;
+    if (!truth(consume(isNonSpace))) return false;
+    zeroOrMore(() => consume(isNonBreak));
+    return true;
+  });
+
+  // 176
+  bool l_nb_foldedLines(int indent) {
+    if (!truth(s_nb_foldedText(indent))) return false;
+    zeroOrMore(() => transaction(() {
+        if (!truth(b_l_folded(indent, BLOCK_IN))) return false;
+        return s_nb_foldedText(indent);
+      }));
+    return true;
+  }
+
+  // 177
+  bool s_nb_spacedText(int indent) => transaction(() {
+    if (!truth(captureAs('', () => s_indent(indent)))) return false;
+    if (!truth(consume(isSpace))) return false;
+    zeroOrMore(() => consume(isNonBreak));
+    return true;
+  });
+
+  // 178
+  bool b_l_spaced(int indent) {
+    if (!truth(b_asLineFeed())) return false;
+    zeroOrMore(() => captureAs("\n", () => l_empty(indent, BLOCK_IN)));
+    return true;
+  }
+
+  // 179
+  bool l_nb_spacedLines(int indent) {
+    if (!truth(s_nb_spacedText(indent))) return false;
+    zeroOrMore(() => transaction(() {
+        if (!truth(b_l_spaced(indent))) return false;
+        return s_nb_spacedText(indent);
+      }));
+    return true;
+  }
+
+  // 180
+  bool l_nb_sameLines(int indent) => transaction(() {
+    zeroOrMore(() => captureAs('\n', () => l_empty(indent, BLOCK_IN)));
+    return or([
+      () => l_nb_foldedLines(indent),
+      () => l_nb_spacedLines(indent)
+    ]);
+  });
+
+  // 181
+  bool l_nb_diffLines(int indent) {
+    if (!truth(l_nb_sameLines(indent))) return false;
+    zeroOrMore(() => transaction(() {
+        if (!truth(b_asLineFeed())) return false;
+        return l_nb_sameLines(indent);
+      }));
+    return true;
+  }
+
+  // 182
+  String l_foldedContent(int indent, int chomping) => captureString(() {
+    transaction(() {
+      if (!truth(l_nb_diffLines(indent))) return false;
+      return b_chompedLast(chomping);
+    });
+    l_chompedEmpty(indent, chomping);
+    return true;
+  });
 
   // 183
   _SequenceNode l_blockSequence(int indent) => context('sequence', () {
     var additionalIndent = countIndentation() - indent;
     if (additionalIndent <= 0) return null;
 
     var content = oneOrMore(() => transaction(() {
-      if (!s_indent(indent + additionalIndent)) return null;
+      if (!truth(s_indent(indent + additionalIndent))) return null;
       return c_l_blockSeqEntry(indent + additionalIndent);
     }));
     if (!truth(content)) return null;
 
     return new _SequenceNode("?", content);
   });
 
   // 184
   _Node c_l_blockSeqEntry(int indent) => transaction(() {
-    if (!c_indicator(C_SEQUENCE_ENTRY)) return null;
+    if (!truth(c_indicator(C_SEQUENCE_ENTRY))) return null;
     if (isNonSpace(peek())) return null;
 
     return s_l_blockIndented(indent, BLOCK_IN);
   });
 
   // 185
   _Node s_l_blockIndented(int indent, int ctx) {
     var additionalIndent = countIndentation();
     return or([
       () => transaction(() {
-        if (!s_indent(additionalIndent)) return null;
+        if (!truth(s_indent(additionalIndent))) return null;
         return or([
           () => ns_l_compactSequence(indent + 1 + additionalIndent),
           () => ns_l_compactMapping(indent + 1 + additionalIndent)]);
       }),
       () => s_l_blockNode(indent, ctx),
       () => s_l_comments() ? e_node() : null]);
   }
 
   // 186
   _Node ns_l_compactSequence(int indent) => context('sequence', () {
     var first = c_l_blockSeqEntry(indent);
     if (!truth(first)) return null;
 
     var content = zeroOrMore(() => transaction(() {
-        if (!s_indent(indent)) return null;
+        if (!truth(s_indent(indent))) return null;
         return c_l_blockSeqEntry(indent);
       }));
     content.insertRange(0, 1, first);
 
     return new _SequenceNode("?", content);
   });
 
   // 187
   _Node l_blockMapping(int indent) => context('mapping', () {
     var additionalIndent = countIndentation() - indent;
     if (additionalIndent <= 0) return null;
 
     var pairs = oneOrMore(() => transaction(() {
-      if (!s_indent(indent + additionalIndent)) return null;
+      if (!truth(s_indent(indent + additionalIndent))) return null;
       return ns_l_blockMapEntry(indent + additionalIndent);
     }));
     if (!truth(pairs)) return null;
 
     return map(pairs);
   });
 
   // 188
   _Pair<_Node, _Node> ns_l_blockMapEntry(int indent) => or([
     () => c_l_blockMapExplicitEntry(indent),
     () => ns_l_blockMapImplicitEntry(indent)
   ]);
 
   // 189
-  // TODO(nweiz): implement
-  _Pair<_Node, _Node> c_l_blockMapExplicitEntry(int indent) => null;
+  _Pair<_Node, _Node> c_l_blockMapExplicitEntry(int indent) {
+    var key = c_l_blockMapExplicitKey(indent);
+    if (!truth(key)) return null;
+
+    var value = or([
+      () => l_blockMapExplicitValue(indent),
+      e_node
+    ]);
+
+    return new _Pair<_Node, _Node>(key, value);
+  }
+
+  // 190
+  _Node c_l_blockMapExplicitKey(int indent) => transaction(() {
+    if (!truth(c_indicator(C_MAPPING_KEY))) return null;
+    return s_l_blockIndented(indent, BLOCK_OUT);
+  });
+
+  // 191
+  _Node l_blockMapExplicitValue(int indent) => transaction(() {
+    if (!truth(s_indent(indent))) return null;
+    if (!truth(c_indicator(C_MAPPING_VALUE))) return null;
+    return s_l_blockIndented(indent, BLOCK_OUT);
+  });
 
   // 192
   _Pair<_Node, _Node> ns_l_blockMapImplicitEntry(int indent) => transaction(() {
     var key = or([ns_s_blockMapImplicitKey, e_node]);
     var value = c_l_blockMapImplicitValue(indent);
     return truth(value) ? new _Pair<_Node, _Node>(key, value) : null;
   });
 
   // 193
   _Node ns_s_blockMapImplicitKey() => context('mapping key', () => or([
     () => c_s_implicitJsonKey(BLOCK_KEY),
-    () => c_s_implicitYamlKey(BLOCK_KEY)
+    () => ns_s_implicitYamlKey(BLOCK_KEY)
   ]));
 
   // 194
   _Node c_l_blockMapImplicitValue(int indent) => context('mapping value', () =>
     transaction(() {
-      if (!c_indicator(C_MAPPING_VALUE)) return null;
+      if (!truth(c_indicator(C_MAPPING_VALUE))) return null;
       return or([
         () => s_l_blockNode(indent, BLOCK_OUT),
         () => s_l_comments() ? e_node() : null
       ]);
     }));
 
   // 195
   _Node ns_l_compactMapping(int indent) => context('mapping', () {
     var first = ns_l_blockMapEntry(indent);
     if (!truth(first)) return null;
 
     var pairs = zeroOrMore(() => transaction(() {
-        if (!s_indent(indent)) return null;
+        if (!truth(s_indent(indent))) return null;
         return ns_l_blockMapEntry(indent);
       }));
     pairs.insertRange(0, 1, first);
 
     return map(pairs);
   });
 
   // 196
   _Node s_l_blockNode(int indent, int ctx) => or([
     () => s_l_blockInBlock(indent, ctx),
     () => s_l_flowInBlock(indent)
   ]);
 
   // 197
   _Node s_l_flowInBlock(int indent) => transaction(() {
-    if (!s_separate(indent + 1, FLOW_OUT)) return null;
+    if (!truth(s_separate(indent + 1, FLOW_OUT))) return null;
     var node = ns_flowNode(indent + 1, FLOW_OUT);
     if (!truth(node)) return null;
-    if (!s_l_comments()) return null;
+    if (!truth(s_l_comments())) return null;
     return node;
   });
 
   // 198
   _Node s_l_blockInBlock(int indent, int ctx) => or([
     () => s_l_blockScalar(indent, ctx),
     () => s_l_blockCollection(indent, ctx)
   ]);
 
   // 199
   _Node s_l_blockScalar(int indent, int ctx) => transaction(() {
-    if (!s_separate(indent + 1, ctx)) return null;
+    if (!truth(s_separate(indent + 1, ctx))) return null;
     var props = transaction(() {
       var props = c_ns_properties(indent + 1, ctx);
       if (!truth(props)) return null;
-      if (!s_separate(indent + 1, ctx)) return null;
+      if (!truth(s_separate(indent + 1, ctx))) return null;
       return props;
     });
-    if (!truth(props)) props = new _Pair<_Tag, String>(null, null);
 
     var node = or([() => c_l_literal(indent), () => c_l_folded(indent)]);
     if (!truth(node)) return null;
     return addProps(node, props);
   });
 
   // 200
   _Node s_l_blockCollection(int indent, int ctx) => transaction(() {
     var props = transaction(() {
-      if (!s_separate(indent + 1, ctx)) return null;
+      if (!truth(s_separate(indent + 1, ctx))) return null;
       return c_ns_properties(indent + 1, ctx);
     });
-    if (!truth(props)) props = new _Pair<_Tag, String>(null, null);
 
-    if (!s_l_comments()) return null;
+    if (!truth(s_l_comments())) return null;
     return or([
       () => l_blockSequence(seqSpaces(indent, ctx)),
       () => l_blockMapping(indent)]);
   });
 
   // 201
   int seqSpaces(int indent, int ctx) => ctx == BLOCK_OUT ? indent - 1 : indent;
 
   // 202
   void l_documentPrefix() {
     zeroOrMore(l_comment);
   }
 
   // 203
   bool c_directivesEnd() => rawString("---");
 
   // 204
   bool c_documentEnd() => rawString("...");
 
   // 205
   bool l_documentSuffix() => transaction(() {
-    if (!c_documentEnd()) return false;
+    if (!truth(c_documentEnd())) return false;
     return s_l_comments();
   });
 
   // 206
   bool c_forbidden() {
     if (!inBareDocument || !atStartOfLine) return false;
     var forbidden = false;
     transaction(() {
       if (!truth(or([c_directivesEnd, c_documentEnd]))) return;
       var char = peek();
       forbidden = isBreak(char) || isSpace(char) || atEndOfFile;
       return;
     });
     return forbidden;
   }
 
   // 207
   _Node l_bareDocument() {
     try {
       inBareDocument = true;
       return s_l_blockNode(-1, BLOCK_IN);
     } finally {
       inBareDocument = false;
     }
   }
 
   // 208
   _Node l_explicitDocument() {
-    if (!c_directivesEnd()) return null;
+    if (!truth(c_directivesEnd())) return null;
     var doc = l_bareDocument();
     if (truth(doc)) return doc;
 
     doc = e_node();
     s_l_comments();
     return doc;
   }
 
   // 209
   _Node l_directiveDocument() {
@@ skipping 44 matching lines @@
 
 /** A pair of values. */
 class _Pair<E, F> {
   E first;
   F last;
 
   _Pair(this.first, this.last);
 
   String toString() => '($first, $last)';
 }
+
+/** The information in the header for a block scalar. */
+class _BlockHeader {
+  final int additionalIndent;
+  final int chomping;
+
+  _BlockHeader(this.additionalIndent, this.chomping);
+
+  bool get autoDetectIndent() => additionalIndent == null;
+}