Add observatory_pub_packages snapshot to third_party

observatory_pub_packages/html5lib/dom_parsing.dart

+/// This library contains extra APIs that aren't in the DOM, but are useful
+/// when interacting with the parse tree.
+library dom_parsing;
+
+import 'dom.dart';
+import 'src/constants.dart' show rcdataElements;
+
+/// A simple tree visitor for the DOM nodes.
+class TreeVisitor {
+  visit(Node node) {
+    switch (node.nodeType) {
+      case Node.ELEMENT_NODE: return visitElement(node);
+      case Node.TEXT_NODE: return visitText(node);
+      case Node.COMMENT_NODE: return visitComment(node);
+      case Node.DOCUMENT_FRAGMENT_NODE: return visitDocumentFragment(node);
+      case Node.DOCUMENT_NODE: return visitDocument(node);
+      case Node.DOCUMENT_TYPE_NODE: return visitDocumentType(node);
+      default: throw new UnsupportedError('DOM node type ${node.nodeType}');
+    }
+  }
+
+  visitChildren(Node node) {
+    // Allow for mutations (remove works) while iterating.
+    for (var child in node.nodes.toList()) visit(child);
+  }
+
+  /// The fallback handler if the more specific visit method hasn't been
+  /// overriden. Only use this from a subclass of [TreeVisitor], otherwise
+  /// call [visit] instead.
+  visitNodeFallback(Node node) => visitChildren(node);
+
+  visitDocument(Document node) => visitNodeFallback(node);
+
+  visitDocumentType(DocumentType node) => visitNodeFallback(node);
+
+  visitText(Text node) => visitNodeFallback(node);
+
+  // TODO(jmesserly): visit attributes.
+  visitElement(Element node) => visitNodeFallback(node);
+
+  visitComment(Comment node) => visitNodeFallback(node);
+
+  visitDocumentFragment(DocumentFragment node) => visitNodeFallback(node);
+}
+
+/// Converts the DOM tree into an HTML string with code markup suitable for
+/// displaying the HTML's source code with CSS colors for different parts of the
+/// markup. See also [CodeMarkupVisitor].
+String htmlToCodeMarkup(Node node) {
+  return (new CodeMarkupVisitor()..visit(node)).toString();
+}
+
+/// Converts the DOM tree into an HTML string with code markup suitable for
+/// displaying the HTML's source code with CSS colors for different parts of the
+/// markup. See also [htmlToCodeMarkup].
+class CodeMarkupVisitor extends TreeVisitor {
+  final StringBuffer _str;
+
+  CodeMarkupVisitor() : _str = new StringBuffer();
+
+  String toString() => _str.toString();
+
+  visitDocument(Document node) {
+    _str.write("<pre>");
+    visitChildren(node);
+    _str.write("</pre>");
+  }
+
+  visitDocumentType(DocumentType node) {
+    _str.write('<code class="markup doctype">&lt;!DOCTYPE ${node.name}>'
+        '</code>');
+  }
+
+  visitText(Text node) {
+    writeTextNodeAsHtml(_str, node);
+  }
+
+  visitElement(Element node) {
+    final tag = node.localName;
+    _str.write('&lt;<code class="markup element-name">$tag</code>');
+    if (node.attributes.length > 0) {
+      node.attributes.forEach((key, v) {
+        v = htmlSerializeEscape(v, attributeMode: true);
+        _str.write(' <code class="markup attribute-name">$key</code>'
+            '=<code class="markup attribute-value">"$v"</code>');
+      });
+    }
+    if (node.nodes.length > 0) {
+      _str.write(">");
+      visitChildren(node);
+    } else if (isVoidElement(tag)) {
+      _str.write(">");
+      return;
+    }
+    _str.write(
+        '&lt;/<code class="markup element-name">$tag</code>>');
+  }
+
+  visitComment(Comment node) {
+    var data = htmlSerializeEscape(node.data);
+    _str.write('<code class="markup comment">&lt;!--${data}--></code>');
+  }
+}
+
+
+// TODO(jmesserly): reconcile this with dart:web htmlEscape.
+// This one might be more useful, as it is HTML5 spec compliant.
+/// Escapes [text] for use in the
+/// [HTML fragment serialization algorithm][1]. In particular, as described
+/// in the [specification][2]:
+///
+/// - Replace any occurrence of the `&` character by the string `&amp;`.
+/// - Replace any occurrences of the U+00A0 NO-BREAK SPACE character by the
+///   string `&nbsp;`.
+/// - If the algorithm was invoked in [attributeMode], replace any occurrences
+///   of the `"` character by the string `&quot;`.
+/// - If the algorithm was not invoked in [attributeMode], replace any
+///   occurrences of the `<` character by the string `&lt;`, and any occurrences
+///   of the `>` character by the string `&gt;`.
+///
+/// [1]: http://www.whatwg.org/specs/web-apps/current-work/multipage/the-end.html#serializing-html-fragments
+/// [2]: http://www.whatwg.org/specs/web-apps/current-work/multipage/the-end.html#escapingString
+String htmlSerializeEscape(String text, {bool attributeMode: false}) {
+  // TODO(jmesserly): is it faster to build up a list of codepoints?
+  // StringBuffer seems cleaner assuming Dart can unbox 1-char strings.
+  StringBuffer result = null;
+  for (int i = 0; i < text.length; i++) {
+    var ch = text[i];
+    String replace = null;
+    switch (ch) {
+      case '&': replace = '&amp;'; break;
+      case '\u00A0'/*NO-BREAK SPACE*/: replace = '&nbsp;'; break;
+      case '"': if (attributeMode) replace = '&quot;'; break;
+      case '<': if (!attributeMode) replace = '&lt;'; break;
+      case '>': if (!attributeMode) replace = '&gt;'; break;
+    }
+    if (replace != null) {
+      if (result == null) result = new StringBuffer(text.substring(0, i));
+      result.write(replace);
+    } else if (result != null) {
+      result.write(ch);
+    }
+  }
+
+  return result != null ? result.toString() : text;
+}
+
+
+/// Returns true if this tag name is a void element.
+/// This method is useful to a pretty printer, because void elements must not
+/// have an end tag.
+/// See also: <http://dev.w3.org/html5/markup/syntax.html#void-elements>.
+bool isVoidElement(String tagName) {
+  switch (tagName) {
+    case "area": case "base": case "br": case "col": case "command":
+    case "embed": case "hr": case "img": case "input": case "keygen":
+    case "link": case "meta": case "param": case "source": case "track":
+    case "wbr":
+      return true;
+  }
+  return false;
+}
+
+/// Serialize text node according to:
+/// <http://www.whatwg.org/specs/web-apps/current-work/multipage/the-end.html#html-fragment-serialization-algorithm>
+void writeTextNodeAsHtml(StringBuffer str, Text node) {
+  // Don't escape text for certain elements, notably <script>.
+  final parent = node.parentNode;
+  if (parent is Element) {
+    var tag = parent.localName;
+    if (rcdataElements.contains(tag) || tag == 'plaintext') {
+      str.write(node.data);
+      return;
+    }
+  }
+  str.write(htmlSerializeEscape(node.data));
+}