adding HtmlEscape to dart:convert

sdk/lib/convert/html_escape.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.
+
+part of dart.convert;
+
+// TODO(floitsch) - Document - Issue 13097
+const HTML_ESCAPE = const HtmlEscape();
+
+class HtmlEscapeMode {

[Jennifer Messerly, 2013/09/05 20:41:37]

nit: I think you could just have one TODO about the documentation issue on the
class:

// TODO(floitsch) - Document - Issue 13097

+  final String _name;
+  final bool escapeLtGt;
+  final bool escapeQuot;
+  final bool escapeApos;
+
+  // TODO(floitsch) - Document - Issue 13097
+  static const HtmlEscapeMode UNKNOWN =

[Jennifer Messerly, 2013/09/05 20:41:37]

suggestion: rename UNKNOWN_QUOTED_ATTRIBUTE

(the current escaping rules are not be safe to use in an unknown context or
unquoted attributes)

suggested documentation comment:

/**
 * Escape the string for use in an HTML quoted attribute context, when it
 * is not known if the HTML uses single or double quotes.
 *
 * This will escape less-than `<`, greater-than `>`, single-quote `'`, 
 * double-quote `"`, ampersand `&`, and no-break-space `U+00A0`.
 */

+    const HtmlEscapeMode._('unknown', true, true, true);
+
+  // TODO(floitsch) - Document - Issue 13097
+  static const HtmlEscapeMode ATTRIBUTE =

[Jennifer Messerly, 2013/09/05 20:41:37]

DOUBLE_QUOTE_ATTRIBUTE

and add SINGLE_QUOTE_ATTRIBUTE variant.


alternatively:

QUOTED_ATTRIBUTE

that escapes single and double quote.

+    const HtmlEscapeMode._('attribute', false, true, false);

[Jennifer Messerly, 2013/09/05 20:41:37]

Shouldn't this include less than and greater than as well? even the relatively
minimalist DOM serializer escapes those even in doube quoted attributes

[kevmoo-old, 2013/09/07 20:34:15]

The argument is that they are unneeded. Only in elements. If one wants to be
paranoid, use the default behavior.

+
+  // TODO(floitsch) - Document - Issue 13097
+  static const HtmlEscapeMode ELEMENT =

[Jennifer Messerly, 2013/09/05 20:41:37]

ELEMENT_CONTENT

+    const HtmlEscapeMode._('element', true, false, false);
+
+  // TODO(floitsch) - Document - Issue 13097
+  const HtmlEscapeMode._(this._name, this.escapeLtGt, this.escapeQuot,

[Jennifer Messerly, 2013/09/05 20:41:37]

named arguments to make call the definitions more readable?

[kevmoo-old, 2013/09/07 20:34:15]

Agreed.

+    this.escapeApos);
+
+  String toString() => _name;
+}
+
+  // TODO(floitsch) - Document - Issue 13097
+class HtmlEscape extends Converter<String, String> {
+
+  // TODO(floitsch) - Document - Issue 13097
+  final HtmlEscapeMode mode;
+
+  // TODO(floitsch) - Document - Issue 13097
+  const HtmlEscape([this.mode = HtmlEscapeMode.UNKNOWN]);
+
+  String convert(String text) {
+    var val = _convert(text, 0, text.length);
+    return val == null ? text : val;
+  }
+
+  String _convert(String text, int start, int end) {
+    StringBuffer result = null;
+    for (int i = start; i < end; i++) {
+      var ch = text[i];
+      String replace = null;
+      switch (ch) {
+        case '&': replace = '&amp;'; break;
+        case '\u00A0'/*NO-BREAK SPACE*/: replace = '&nbsp;'; break;
+        case '"': if (mode.escapeQuot) replace = '&quot;'; break;
+        case "'": if (mode.escapeApos) replace = '&apos;'; break;
+        case '<': if (mode.escapeLtGt) replace = '&lt;'; break;
+        case '>': if (mode.escapeLtGt) replace = '&gt;'; break;
+      }
+      if (replace != null) {
+        if (result == null) result = new StringBuffer(text.substring(start, i));
+        result.write(replace);
+      } else if (result != null) {
+        result.write(ch);
+      }
+    }
+
+    return result != null ? result.toString() : null;
+  }
+
+  StringConversionSink startChunkedConversion(
+    ChunkedConversionSink<String> sink) {
+
+    if (sink is! StringConversionSink) {
+      sink = new StringConversionSink.from(sink);
+    }
+    return new _HtmlEscapeSink(this, sink);
+  }
+}
+
+class _HtmlEscapeSink extends StringConversionSinkBase {
+  final HtmlEscape _escape;
+  final StringConversionSink _sink;
+
+  _HtmlEscapeSink(this._escape, this._sink);
+
+  void addSlice(String chunk, int start, int end, bool isLast) {
+    var val = _escape._convert(chunk, start, end);
+    if(val == null) {
+      _sink.addSlice(chunk, start, end, isLast);
+    } else {
+      _sink.add(val);
+      if (isLast) _sink.close();
+    }
+  }
+
+  void close() => _sink.close();
+}