First pass at a markdown parser in Dart.

utils/markdown/test/markdown_tests.dart

+// Copyright (c) 2011, 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.
+
+/// Unit tests for markdown.
+#library('markdown_tests');
+
+#import('../lib.dart');
+
+// TODO(rnystrom): Better path to unittest.
+#import('../../../client/testing/unittest/unittest_vm.dart');
+
+/// Most of these tests are based on observing how showdown behaves:
+/// http://softwaremaniacs.org/playground/showdown-highlight/
+void main() {
+  group('Paragraphs', () {
+    validate('consecutive lines form a single paragraph', '''
+        This is the first line.
+        This is the second line.
+        ''', '''
+        <p>This is the first line.
+        This is the second line.</p>
+        ''');
+
+    // TODO(rnystrom): The rules here for what happens to lines following a
+    // paragraph appear to be completely arbitrary in markdown. If it makes the
+    // code significantly cleaner, we should consider ourselves free to change
+    // these tests.
+
+    validate('are terminated by a header', '''
+        para
+        # header
+        ''', '''
+        <p>para</p>
+        <h1>header</h1>
+        ''');
+
+    validate('are terminated by a setext header', '''
+        para
+        header
+        ==
+        ''', '''
+        <p>para</p>
+        <h1>header</h1>
+        ''');
+
+    validate('are terminated by a hr', '''
+        para
+        ___
+        ''', '''
+        <p>para</p>
+        <hr />
+        ''');
+
+    validate('consume an unordered list', '''
+        para
+        * list
+        ''', '''
+        <p>para
+        * list</p>
+        ''');
+
+    validate('consume an ordered list', '''
+        para
+        1. list
+        ''', '''
+        <p>para
+        1. list</p>
+        ''');
+  });
+
+  group('Setext headers', () {
+    validate('h1', '''
+        text
+        ===
+        ''', '''
+        <h1>text</h1>
+        ''');
+
+    validate('h2', '''
+        text
+        ---
+        ''', '''
+        <h2>text</h2>
+        ''');
+
+    validate('h1 on first line becomes text', '''
+        ===
+        ''', '''
+        <p>===</p>
+        ''');
+
+    validate('h2 on first line becomes text', '''
+        -
+        ''', '''
+        <p>-</p>
+        ''');
+
+    validate('h1 turns preceding list into text', '''
+        - list
+        ===
+        ''', '''
+        <h1>- list</h1>
+        ''');
+
+    validate('h2 turns preceding list into text', '''
+        - list
+        ===
+        ''', '''
+        <h1>- list</h1>
+        ''');
+
+    validate('h1 turns preceding blockquote into text', '''
+        > quote
+        ===
+        ''', '''
+        <h1>> quote</h1>
+        ''');
+
+    validate('h2 turns preceding blockquote into text', '''
+        > quote
+        ===
+        ''', '''
+        <h1>> quote</h1>
+        ''');
+  });
+
+  group('Headers', () {
+    validate('h1', '''
+        # header
+        ''', '''
+        <h1>header</h1>
+        ''');
+
+    validate('h2', '''
+        ## header
+        ''', '''
+        <h2>header</h2>
+        ''');
+
+    validate('h3', '''
+        ### header
+        ''', '''
+        <h3>header</h3>
+        ''');
+
+    validate('h4', '''
+        #### header
+        ''', '''
+        <h4>header</h4>
+        ''');
+
+    validate('h5', '''
+        ##### header
+        ''', '''
+        <h5>header</h5>
+        ''');
+
+    validate('h6', '''
+        ###### header
+        ''', '''
+        <h6>header</h6>
+        ''');
+
+    validate('trailing "#" are removed', '''
+        # header ######
+        ''', '''
+        <h1>header</h1>
+        ''');
+
+  });
+
+  group('Unordered lists', () {
+    validate('asterisk, plus and hyphen', '''
+        * star
+        - dash
+        + plus
+        ''', '''
+        <ul>
+          <li>star</li>
+          <li>dash</li>
+          <li>plus</li>
+        </ul>
+        ''');
+
+    validate('allow numbered lines after first', '''
+        * a
+        1. b
+        ''', '''
+        <ul>
+          <li>a</li>
+          <li>b</li>
+        </ul>
+        ''');
+
+    validate('allow a tab after the marker', '''
+        *\ta
+        +\tb
+        -\tc
+        1.\td
+        ''', '''
+        <ul>
+          <li>a</li>
+          <li>b</li>
+          <li>c</li>
+          <li>d</li>
+        </ul>
+        ''');
+
+    validate('wrap items in paragraphs if blank lines separate', '''
+        * one
+
+        * two
+        ''', '''
+        <ul>
+          <li><p>one</p></li>
+          <li><p>two</p></li>
+        </ul>
+        ''');
+
+    validate('force paragraph on item before and after blank lines', '''
+        *   one
+        *   two
+
+        *   three
+        ''', '''
+        <ul>
+          <li>one</li>
+          <li>
+            <p>two</p>
+          </li>
+          <li>
+            <p>three</p>
+          </li>
+        </ul>
+        ''');
+
+    validate('do not force paragraph if item is already block', '''
+        * > quote
+
+        * # header
+        ''', '''
+        <ul>
+          <li><blockquote><p>quote</p></blockquote></li>
+          <li><h1>header</h1></li>
+        </ul>
+        ''');
+
+    validate('can contain multiple paragraphs', '''
+        *   one
+
+            two
+
+        *   three
+        ''', '''
+        <ul>
+          <li>
+            <p>one</p>
+            <p>two</p>
+          </li>
+          <li>
+            <p>three</p>
+          </li>
+        </ul>
+        ''');
+
+    // TODO(rnystrom): This is how most other markdown parsers handle
+    // this but that seems like a nasty special case. For now, let's not
+    // worry about it.
+    /*
+    validate('can nest using indentation', '''
+        *   parent
+            *   child
+        ''', '''
+        <ul>
+        <li>parent
+        <ul><li>child</li></ul></li>
+        </ul>
+        ''');
+    */
+  });
+
+  group('Ordered lists', () {
+    validate('start with numbers', '''
+        1. one
+        45.  two
+           12345. three
+        ''', '''
+        <ol>
+          <li>one</li>
+          <li>two</li>
+          <li>three</li>
+        </ol>
+        ''');
+
+    validate('allow unordered lines after first', '''
+        1. a
+        * b
+        ''', '''
+        <ol>
+          <li>a</li>
+          <li>b</li>
+        </ol>
+        ''');
+  });
+
+  group('Blockquotes', () {
+    validate('single line', '''
+        > blah
+        ''', '''
+        <blockquote>
+          <p>blah</p>
+        </blockquote>
+        ''');
+
+    validate('with two paragraphs', '''
+        > first
+        >
+        > second
+        ''', '''
+        <blockquote>
+          <p>first</p>
+          <p>second</p>
+        </blockquote>
+        ''');
+
+    validate('nested', '''
+        > one
+        >> two
+        > > > three
+        ''', '''
+        <blockquote>
+          <p>one</p>
+          <blockquote>
+            <p>two</p>
+            <blockquote>
+              <p>three</p>
+            </blockquote>
+          </blockquote>
+        </blockquote>
+        ''');
+  });
+
+  group('Code blocks', () {
+    validate('single line', '''
+            code
+        ''', '''
+        <pre><code>code</code></pre>
+        ''');
+
+    validate('include leading whitespace after indentation', '''
+            zero
+             one
+              two
+               three
+        ''', '''
+        <pre><code>zero
+         one
+          two
+           three</code></pre>
+        ''');
+
+    validate('escape HTML characters', '''
+            <&>
+        ''', '''
+        <pre><code>&lt;&amp;&gt;</code></pre>
+        ''');
+  });
+
+  group('Horizontal rules', () {
+    validate('from dashes', '''
+        ---
+        ''', '''
+        <hr />
+        ''');
+
+    validate('from asterisks', '''
+        ***
+        ''', '''
+        <hr />
+        ''');
+
+    validate('from underscores', '''
+        ___
+        ''', '''
+        <hr />
+        ''');
+
+    validate('can include up to two spaces', '''
+        _ _  _
+        ''', '''
+        <hr />
+        ''');
+  });
+
+  group('Block-level HTML', () {
+    validate('single line', '''
+        <table></table>
+        ''', '''
+        <table></table>
+        ''');
+
+    validate('multi-line', '''
+        <table>
+            blah
+        </table>
+        ''', '''
+        <table>
+            blah
+        </table>
+        ''');
+
+    validate('blank line ends block', '''
+        <table>
+            blah
+        </table>
+
+        para
+        ''', '''
+        <table>
+            blah
+        </table>
+        <p>para</p>
+        ''');
+
+    validate('HTML can be bogus', '''
+        <bogus>
+        blah
+        </weird>
+
+        para
+        ''', '''
+        <bogus>
+        blah
+        </weird>
+        <p>para</p>
+        ''');
+  });
+
+  group('Strong', () {
+    validate('using asterisks', '''
+        before **strong** after
+        ''', '''
+        <p>before <strong>strong</strong> after</p>
+        ''');
+
+    validate('using underscores', '''
+        before __strong__ after
+        ''', '''
+        <p>before <strong>strong</strong> after</p>
+        ''');
+
+    validate('unmatched asterisks', '''
+        before ** after
+        ''', '''
+        <p>before ** after</p>
+        ''');
+
+    validate('unmatched underscores', '''
+        before __ after
+        ''', '''
+        <p>before __ after</p>
+        ''');
+
+    validate('multiple spans in one text', '''
+        a **one** b __two__ c
+        ''', '''
+        <p>a <strong>one</strong> b <strong>two</strong> c</p>
+        ''');
+
+    validate('multi-line', '''
+        before **first
+        second** after
+        ''', '''
+        <p>before <strong>first
+        second</strong> after</p>
+        ''');
+  });
+
+  group('Emphasis and strong', () {
+    validate('single asterisks', '''
+        before *em* after
+        ''', '''
+        <p>before <em>em</em> after</p>
+        ''');
+
+    validate('single underscores', '''
+        before _em_ after
+        ''', '''
+        <p>before <em>em</em> after</p>
+        ''');
+
+    validate('double asterisks', '''
+        before **strong** after
+        ''', '''
+        <p>before <strong>strong</strong> after</p>
+        ''');
+
+    validate('double underscores', '''
+        before __strong__ after
+        ''', '''
+        <p>before <strong>strong</strong> after</p>
+        ''');
+
+    validate('unmatched asterisk', '''
+        before *after
+        ''', '''
+        <p>before *after</p>
+        ''');
+
+    validate('unmatched underscore', '''
+        before _after
+        ''', '''
+        <p>before _after</p>
+        ''');
+
+    validate('multiple spans in one text', '''
+        a *one* b _two_ c
+        ''', '''
+        <p>a <em>one</em> b <em>two</em> c</p>
+        ''');
+
+    validate('multi-line', '''
+        before *first
+        second* after
+        ''', '''
+        <p>before <em>first
+        second</em> after</p>
+        ''');
+
+    validate('not processed when surrounded by spaces', '''
+        a * b * c _ d _ e
+        ''', '''
+        <p>a * b * c _ d _ e</p>
+        ''');
+
+    validate('strong then emphasis', '''
+        **strong***em*
+        ''', '''
+        <p><strong>strong</strong><em>em</em></p>
+        ''');
+
+    validate('emphasis then strong', '''
+        *em***strong**
+        ''', '''
+        <p><em>em</em><strong>strong</strong></p>
+        ''');
+
+    validate('emphasis inside strong', '''
+        **strong *em***
+        ''', '''
+        <p><strong>strong <em>em</em></strong></p>
+        ''');
+
+    validate('mismatched in nested', '''
+        *a _b* c_
+        ''', '''
+        <p><em>a _b</em> c_</p>
+        ''');
+
+    validate('cannot nest tags of same type', '''
+        *a _b *c* d_ e*
+        ''', '''
+        <p><em>a _b </em>c<em> d_ e</em></p>
+        ''');
+  });
+
+  group('Inline code', () {
+    validate('simple case', '''
+        before `source` after
+        ''', '''
+        <p>before <code>source</code> after</p>
+        ''');
+
+    validate('unmatched backtick', '''
+        before ` after
+        ''', '''
+        <p>before ` after</p>
+        ''');
+    validate('multiple spans in one text', '''
+        a `one` b `two` c
+        ''', '''
+        <p>a <code>one</code> b <code>two</code> c</p>
+        ''');
+
+    validate('multi-line', '''
+        before `first
+        second` after
+        ''', '''
+        <p>before <code>first
+        second</code> after</p>
+        ''');
+
+    validate('double backticks', '''
+        before ``can `contain` backticks`` after
+        ''', '''
+        <p>before <code>can `contain` backticks</code> after</p>
+        ''');
+
+    validate('double backticks with spaces', '''
+        before `` `tick` `` after
+        ''', '''
+        <p>before <code>`tick`</code> after</p>
+        ''');
+
+    validate('ignore markup inside code', '''
+        before `*b* _c_` after
+        ''', '''
+        <p>before <code>*b* _c_</code> after</p>
+        ''');
+
+    validate('escape HTML characters', '''
+        `<&>`
+        ''', '''
+        <p><code>&lt;&amp;&gt;</code></p>
+        ''');
+  });
+
+  group('HTML encoding', () {
+    validate('less than and ampersand are escaped', '''
+        < &
+        ''', '''
+        <p>&lt; &amp;</p>
+        ''');
+    validate('greater than is not escaped', '''
+        not you >
+        ''', '''
+        <p>not you ></p>
+        ''');
+    validate('existing entities are untouched', '''
+        &amp;
+        ''', '''
+        <p>&amp;</p>
+        ''');
+  });
+
+  group('Autolinks', () {
+    validate('basic link', '''
+        before <http://foo.com/> after
+        ''', '''
+        <p>before <a href="http://foo.com/">http://foo.com/</a> after</p>
+        ''');
+    validate('handles ampersand in url', '''
+        <http://foo.com/?a=1&b=2>
+        ''', '''
+        <p><a href="http://foo.com/?a=1&b=2">http://foo.com/?a=1&amp;b=2</a></p>
+        ''');
+  });
+
+  group('Reference links', () {
+    validate('double quotes for title', '''
+        links [are] [a] awesome
+
+        [a]: http://foo.com "woo"
+        ''', '''
+        <p>links <a href="http://foo.com" title="woo">are</a> awesome</p>
+        ''');
+    validate('single quoted title', """
+        links [are] [a] awesome
+
+        [a]: http://foo.com 'woo'
+        """, '''
+        <p>links <a href="http://foo.com" title="woo">are</a> awesome</p>
+        ''');
+    validate('parentheses for title', '''
+        links [are] [a] awesome
+
+        [a]: http://foo.com (woo)
+        ''', '''
+        <p>links <a href="http://foo.com" title="woo">are</a> awesome</p>
+        ''');
+    validate('no title', '''
+        links [are] [a] awesome
+
+        [a]: http://foo.com
+        ''', '''
+        <p>links <a href="http://foo.com">are</a> awesome</p>
+        ''');
+    validate('unknown link becomes plaintext', '''
+        [not] [known]
+        ''', '''
+        <p>[not] [known]</p>
+        ''');
+    validate('can style link contents', '''
+        links [*are*] [a] awesome
+
+        [a]: http://foo.com
+        ''', '''
+        <p>links <a href="http://foo.com"><em>are</em></a> awesome</p>
+        ''');
+  });
+
+  group('Inline links', () {
+    validate('double quotes for title', '''
+        links [are](http://foo.com "woo") awesome
+        ''', '''
+        <p>links <a href="http://foo.com" title="woo">are</a> awesome</p>
+        ''');
+    validate('no title', '''
+        links [are] (http://foo.com) awesome
+        ''', '''
+        <p>links <a href="http://foo.com">are</a> awesome</p>
+        ''');
+    validate('can style link contents', '''
+        links [*are*](http://foo.com) awesome
+        ''', '''
+        <p>links <a href="http://foo.com"><em>are</em></a> awesome</p>
+        ''');
+  });
+}
+
+validate(String description, String markdown, String html) {
+  test(description, () {
+    markdown = cleanUpLiteral(markdown);
+    html = cleanUpLiteral(html);
+
+    var result = markdownToHtml(markdown);
+    var passed = compareOutput(html, result);
+
+    if (!passed) {
+      // Remove trailing newline.
+      html = html.substring(0, html.length - 1);
+
+      print('FAIL: $description');
+      print('  expect: ${html.replaceAll("\n", "\n          ")}');
+      print('  actual: ${result.replaceAll("\n", "\n          ")}');
+      print('');
+    }
+
+    expect(passed).isTrue();
+  });
+}
+
+/// The tests uses triple-quoted strings, which will include leading indentation
+/// to make them look nice in code. But we don't want the markdown parser to
+/// actually see that, so this cleans it all up.
+///
+/// Note that this is very sensitive to how the literals are styled. They should
+/// be:
+///     '''
+///     Text starts on own line. Lines up with subsequent lines.
+///     Lines are indented exactly 8 characters from the left margin.
+///     Close is on the same line.'''
+///
+cleanUpLiteral(String text) {
+  var lines = text.split('\n');
+  for (var j = 0; j < lines.length; j++) {
+    if (lines[j].length > 8) {
+      lines[j] = lines[j].substring(8, lines[j].length);
+    } else {
+      lines[j] = '';
+    }
+  }
+
+  return Strings.join(lines, '\n');
+}
+
+/// Does a loose comparison of the two strings of HTML. Ignores differences in
+/// newlines and indentation.
+compareOutput(String a, String b) {
+  int i = 0;
+  int j = 0;
+
+  skipIgnored(String s, int i) {
+    // Ignore newlines.
+    while ((i < s.length) && (s[i] == '\n')) {
+      i++;
+      // Ignore indentation.
+      while ((i < s.length) && (s[i] == ' ')) i++;
+    }
+
+    return i;
+  }
+
+  while (true) {
+    i = skipIgnored(a, i);
+    j = skipIgnored(b, j);
+
+    // If one string runs out of non-ignored strings, the other must too.
+    if (i == a.length) return j == b.length;
+    if (j == b.length) return i == a.length;
+
+    if (a[i] != b[j]) return false;
+    i++;
+    j++;
+  }
+}