Update CommonMark spec to 0.29

fix https://github.com/markdown-it/markdown-it/issues/553

test/fixtures/commonmark/bad.txt

@@ -0,0 +1,289 @@
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+src line: 1884
+
+.
+``` ```
+aaa
+.
+<p><code> </code>
+aaa</p>
+.
+
+error:
+
+<p><code></code>
+aaa</p>
+
+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+src line: 1995
+
+.
+~~~ aa ``` ~~~
+foo
+~~~
+.
+<pre><code class="language-aa">foo
+</code></pre>
+.
+
+error:
+
+<p>~~~ aa ``` ~~~
+foo</p>
+<pre><code></code></pre>
+
+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+src line: 2844
+
+.
+[Foo bar]:
+<my url>
+'title'
+
+[Foo bar]
+.
+<p><a href="my%20url" title="title">Foo bar</a></p>
+.
+
+error:
+
+<p>[Foo bar]:
+<my url>
+'title'</p>
+<p>[Foo bar]</p>
+
+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+src line: 5176
+
+.
+- a
+ - b
+  - c
+   - d
+    - e
+.
+<ul>
+<li>a</li>
+<li>b</li>
+<li>c</li>
+<li>d
+- e</li>
+</ul>
+.
+
+error:
+
+<ul>
+<li>a</li>
+<li>b</li>
+<li>c</li>
+<li>d</li>
+<li>e</li>
+</ul>
+
+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+src line: 5196
+
+.
+1. a
+
+  2. b
+
+    3. c
+.
+<ol>
+<li>
+<p>a</p>
+</li>
+<li>
+<p>b</p>
+</li>
+</ol>
+<pre><code>3. c
+</code></pre>
+.
+
+error:
+
+<ol>
+<li>
+<p>a</p>
+</li>
+<li>
+<p>b</p>
+</li>
+<li>
+<p>c</p>
+</li>
+</ol>
+
+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+src line: 5898
+
+.
+`  ``  `
+.
+<p><code> `` </code></p>
+.
+
+error:
+
+<p><code>``</code></p>
+
+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+src line: 5907
+
+.
+` a`
+.
+<p><code> a</code></p>
+.
+
+error:
+
+<p><code>a</code></p>
+
+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+src line: 5916
+
+.
+` b `
+.
+<p><code> b </code></p>
+.
+
+error:
+
+<p><code>b</code></p>
+
+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+src line: 5924
+
+.
+` `
+`  `
+.
+<p><code> </code>
+<code>  </code></p>
+.
+
+error:
+
+<p><code></code>
+<code></code></p>
+
+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+src line: 5935
+
+.
+``
+foo
+bar  
+baz
+``
+.
+<p><code>foo bar   baz</code></p>
+.
+
+error:
+
+<p><code>foo bar baz</code></p>
+
+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+src line: 5945
+
+.
+``
+foo 
+``
+.
+<p><code>foo </code></p>
+.
+
+error:
+
+<p><code>foo</code></p>
+
+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+src line: 5956
+
+.
+`foo   bar 
+baz`
+.
+<p><code>foo   bar  baz</code></p>
+.
+
+error:
+
+<p><code>foo bar baz</code></p>
+
+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+src line: 6912
+
+.
+foo***bar***baz
+.
+<p>foo<em><strong>bar</strong></em>baz</p>
+.
+
+error:
+
+<p>foo***bar***baz</p>
+
+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+src line: 6918
+
+.
+foo******bar*********baz
+.
+<p>foo<strong><strong><strong>bar</strong></strong></strong>***baz</p>
+.
+
+error:
+
+<p>foo******bar*********baz</p>
+
+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+src line: 7542
+
+.
+[link](</my uri>)
+.
+<p><a href="/my%20uri">link</a></p>
+.
+
+error:
+
+<p>[link](&lt;/my uri&gt;)</p>
+
+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+src line: 9240
+
+.
+`code 
+span`
+.
+<p><code>code  span</code></p>
+.
+
+error:
+
+<p><code>code span</code></p>
+
+

test/fixtures/commonmark/spec.txt

@@ -1,8 +1,8 @@
 ---
 title: CommonMark Spec
 author: John MacFarlane
-version: 0.28
+version: 0.29
-date: '2017-08-01'
+date: '2019-04-06'
 license: '[CC-BY-SA 4.0](http://creativecommons.org/licenses/by-sa/4.0/)'
 ...
 
@@ -248,7 +248,7 @@ satisfactory replacement for a spec.
 
 Because there is no unambiguous spec, implementations have diverged
 considerably.  As a result, users are often surprised to find that
-a document that renders one way on one system (say, a github wiki)
+a document that renders one way on one system (say, a GitHub wiki)
 renders differently on another (say, converting to docbook using
 pandoc).  To make matters worse, because nothing in Markdown counts
 as a "syntax error," the divergence often isn't discovered right away.
@@ -328,8 +328,10 @@ that is not a [whitespace character].
 
 An [ASCII punctuation character](@)
 is `!`, `"`, `#`, `$`, `%`, `&`, `'`, `(`, `)`,
-`*`, `+`, `,`, `-`, `.`, `/`, `:`, `;`, `<`, `=`, `>`, `?`, `@`,
+`*`, `+`, `,`, `-`, `.`, `/` (U+0021–2F), 
-`[`, `\`, `]`, `^`, `_`, `` ` ``, `{`, `|`, `}`, or `~`.
+`:`, `;`, `<`, `=`, `>`, `?`, `@` (U+003A–0040),
+`[`, `\`, `]`, `^`, `_`, `` ` `` (U+005B–0060), 
+`{`, `|`, `}`, or `~` (U+007B–007E).
 
 A [punctuation character](@) is an [ASCII
 punctuation character] or anything in
@@ -514,8 +516,8 @@ one block element does not affect the inline parsing of any other.
 ## Container blocks and leaf blocks
 
 We can divide blocks into two types:
-[container block](@)s,
+[container blocks](@),
-which can contain other blocks, and [leaf block](@)s,
+which can contain other blocks, and [leaf blocks](@),
 which cannot.
 
 # Leaf blocks
@@ -527,7 +529,7 @@ Markdown document.
 
 A line consisting of 0-3 spaces of indentation, followed by a sequence
 of three or more matching `-`, `_`, or `*` characters, each followed
-optionally by any number of spaces, forms a
+optionally by any number of spaces or tabs, forms a
 [thematic break](@).
 
 ```````````````````````````````` example
@@ -825,7 +827,7 @@ Contents are parsed as inlines:
 ````````````````````````````````
 
 
-Leading and trailing blanks are ignored in parsing inline content:
+Leading and trailing [whitespace] is ignored in parsing inline content:
 
 ```````````````````````````````` example
 #                  foo                     
@@ -1024,6 +1026,20 @@ baz*
 baz</em></h1>
 ````````````````````````````````
 
+The contents are the result of parsing the headings's raw
+content as inlines.  The heading's raw content is formed by
+concatenating the lines and removing initial and final
+[whitespace].
+
+```````````````````````````````` example
+  Foo *bar
+baz*→
+====
+.
+<h1>Foo <em>bar
+baz</em></h1>
+````````````````````````````````
+
 
 The underlining can be any length:
 
@@ -1584,8 +1600,8 @@ begins with a code fence, indented no more than three spaces.
 
 The line with the opening code fence may optionally contain some text
 following the code fence; this is trimmed of leading and trailing
-spaces and called the [info string](@).
+whitespace and called the [info string](@). If the [info string] comes
-The [info string] may not contain any backtick
+after a backtick fence, it may not contain any backtick
 characters.  (The reason for this restriction is that otherwise
 some inline code would be incorrectly interpreted as the
 beginning of a fenced code block.)
@@ -1870,7 +1886,7 @@ Code fences (opening and closing) cannot contain internal spaces:
 ``` ```
 aaa
 .
-<p><code></code>
+<p><code> </code>
 aaa</p>
 ````````````````````````````````
 
@@ -1922,9 +1938,11 @@ bar
 
 
 An [info string] can be provided after the opening code fence.
-Opening and closing spaces will be stripped, and the first word, prefixed
+Although this spec doesn't mandate any particular treatment of
-with `language-`, is used as the value for the `class` attribute of the
+the info string, the first word is typically used to specify
-`code` element within the enclosing `pre` element.
+the language of the code block. In HTML output, the language is
+normally indicated by adding a class to the `code` element consisting
+of `language-` followed by the language name.
 
 ```````````````````````````````` example
 ```ruby
@@ -1973,6 +1991,18 @@ foo</p>
 ````````````````````````````````
 
 
+[Info strings] for tilde code blocks can contain backticks and tildes:
+
+```````````````````````````````` example
+~~~ aa ``` ~~~
+foo
+~~~
+.
+<pre><code class="language-aa">foo
+</code></pre>
+````````````````````````````````
+
+
 Closing code fences cannot have [info strings]:
 
 ```````````````````````````````` example
@@ -1991,14 +2021,15 @@ Closing code fences cannot have [info strings]:
 An [HTML block](@) is a group of lines that is treated
 as raw HTML (and will not be escaped in HTML output).
 
-There are seven kinds of [HTML block], which can be defined
+There are seven kinds of [HTML block], which can be defined by their
-by their start and end conditions.  The block begins with a line that
+start and end conditions.  The block begins with a line that meets a
-meets a [start condition](@) (after up to three spaces
+[start condition](@) (after up to three spaces optional indentation).
-optional indentation).  It ends with the first subsequent line that
+It ends with the first subsequent line that meets a matching [end
-meets a matching [end condition](@), or the last line of
+condition](@), or the last line of the document, or the last line of
-the document or other [container block]), if no line is encountered that meets the
+the [container block](#container-blocks) containing the current HTML
-[end condition].  If the first line meets both the [start condition]
+block, if no line is encountered that meets the [end condition].  If
-and the [end condition], the block will contain just that line.
+the first line meets both the [start condition] and the [end
+condition], the block will contain just that line.
 
 1.  **Start condition:**  line begins with the string `<script`,
 `<pre`, or `<style` (case-insensitive), followed by whitespace,
@@ -2029,7 +2060,7 @@ followed by one of the strings (case-insensitive) `address`,
 `footer`, `form`, `frame`, `frameset`,
 `h1`, `h2`, `h3`, `h4`, `h5`, `h6`, `head`, `header`, `hr`,
 `html`, `iframe`, `legend`, `li`, `link`, `main`, `menu`, `menuitem`,
-`meta`, `nav`, `noframes`, `ol`, `optgroup`, `option`, `p`, `param`,
+`nav`, `noframes`, `ol`, `optgroup`, `option`, `p`, `param`,
 `section`, `source`, `summary`, `table`, `tbody`, `td`,
 `tfoot`, `th`, `thead`, `title`, `tr`, `track`, `ul`, followed
 by [whitespace], the end of the line, the string `>`, or
@@ -2037,16 +2068,17 @@ the string `/>`.\
 **End condition:** line is followed by a [blank line].
 
 7.  **Start condition:**  line begins with a complete [open tag]
-or [closing tag] (with any [tag name] other than `script`,
+(with any [tag name] other than `script`,
-`style`, or `pre`) followed only by [whitespace]
+`style`, or `pre`) or a complete [closing tag],
-or the end of the line.\
+followed only by [whitespace] or the end of the line.\
 **End condition:** line is followed by a [blank line].
 
 HTML blocks continue until they are closed by their appropriate
-[end condition], or the last line of the document or other [container block].
+[end condition], or the last line of the document or other [container
-This means any HTML **within an HTML block** that might otherwise be recognised
+block](#container-blocks).  This means any HTML **within an HTML
-as a start condition will be ignored by the parser and passed through as-is,
+block** that might otherwise be recognised as a start condition will
-without changing the parser's state.
+be ignored by the parser and passed through as-is, without changing
+the parser's state.
 
 For instance, `<pre>` within a HTML block started by `<table>` will not affect
 the parser state; as the HTML block was started in by start condition 6, it
@@ -2069,7 +2101,7 @@ _world_.
 </td></tr></table>
 ````````````````````````````````
 
-In this case, the HTML block is terminated by the newline — the `**hello**`
+In this case, the HTML block is terminated by the newline — the `**Hello**`
 text remains verbatim — and regular parsing resumes, with a paragraph,
 emphasised `world` and inline and block HTML following.
 
@@ -2612,7 +2644,8 @@ bar
 
 
 However, a following blank line is needed, except at the end of
-a document, and except for blocks of types 1--5, above:
+a document, and except for blocks of types 1--5, [above][HTML
+block]:
 
 ```````````````````````````````` example
 <div>
@@ -2758,8 +2791,8 @@ an indented code block:
 
 Fortunately, blank lines are usually not necessary and can be
 deleted.  The exception is inside `<pre>` tags, but as described
-above, raw HTML blocks starting with `<pre>` *can* contain blank
+[above][HTML blocks], raw HTML blocks starting with `<pre>`
-lines.
+*can* contain blank lines.
 
 ## Link reference definitions
 
@@ -2811,7 +2844,7 @@ them.
 
 ```````````````````````````````` example
 [Foo bar]:
-<my%20url>
+<my url>
 'title'
 
 [Foo bar]
@@ -2877,6 +2910,29 @@ The link destination may not be omitted:
 <p>[foo]</p>
 ````````````````````````````````
 
+ However, an empty link destination may be specified using
+ angle brackets:
+
+```````````````````````````````` example
+[foo]: <>
+
+[foo]
+.
+<p><a href="">foo</a></p>
+````````````````````````````````
+
+The title must be separated from the link destination by
+whitespace:
+
+```````````````````````````````` example
+[foo]: <bar>(baz)
+
+[foo]
+.
+<p>[foo]: <bar>(baz)</p>
+<p>[foo]</p>
+````````````````````````````````
+
 
 Both title and destination can contain backslash escapes
 and literal backslashes:
@@ -3034,6 +3090,25 @@ and thematic breaks, and it need not be followed by a blank line.
 </blockquote>
 ````````````````````````````````
 
+```````````````````````````````` example
+[foo]: /url
+bar
+===
+[foo]
+.
+<h1>bar</h1>
+<p><a href="/url">foo</a></p>
+````````````````````````````````
+
+```````````````````````````````` example
+[foo]: /url
+===
+[foo]
+.
+<p>===
+<a href="/url">foo</a></p>
+````````````````````````````````
+
 
 Several [link reference definitions]
 can occur one after another, without intervening blank lines.
@@ -3070,6 +3145,17 @@ are defined:
 ````````````````````````````````
 
 
+Whether something is a [link reference definition] is
+independent of whether the link reference it defines is
+used in the document.  Thus, for example, the following
+document contains just a link reference definition, and
+no visible content:
+
+```````````````````````````````` example
+[foo]: /url
+.
+````````````````````````````````
+
 
 ## Paragraphs
 
@@ -3207,7 +3293,7 @@ aaa
 
 # Container blocks
 
-A [container block] is a block that has other
+A [container block](#container-blocks) is a block that has other
 blocks as its contents.  There are two basic kinds of container blocks:
 [block quotes] and [list items].
 [Lists] are meta-containers for [list items].
@@ -3669,9 +3755,8 @@ in some browsers.)
 The following rules define [list items]:
 
 1.  **Basic case.**  If a sequence of lines *Ls* constitute a sequence of
-    blocks *Bs* starting with a [non-whitespace character] and not separated
+    blocks *Bs* starting with a [non-whitespace character], and *M* is a
-    from each other by more than one blank line, and *M* is a list
+    list marker of width *W* followed by 1 ≤ *N* ≤ 4 spaces, then the result
-    marker of width *W* followed by 1 ≤ *N* ≤ 4 spaces, then the result
     of prepending *M* and the following spaces to the first line of
     *Ls*, and indenting subsequent lines of *Ls* by *W + N* spaces, is a
     list item with *Bs* as its contents.  The type of the list item
@@ -3981,8 +4066,7 @@ A start number may not be negative:
 
 2.  **Item starting with indented code.**  If a sequence of lines *Ls*
     constitute a sequence of blocks *Bs* starting with an indented code
-    block and not separated from each other by more than one blank line,
+    block, and *M* is a list marker of width *W* followed by
-    and *M* is a list marker of width *W* followed by
     one space, then the result of prepending *M* and the following
     space to the first line of *Ls*, and indenting subsequent lines of
     *Ls* by *W + 1* spaces, is a list item with *Bs* as its contents.
@@ -4458,9 +4542,10 @@ continued here.</p>
 6.  **That's all.** Nothing that is not counted as a list item by rules
     #1--5 counts as a [list item](#list-items).
 
-The rules for sublists follow from the general rules above.  A sublist
+The rules for sublists follow from the general rules
-must be indented the same number of spaces a paragraph would need to be
+[above][List items].  A sublist must be indented the same number
-in order to be included in the list item.
+of spaces a paragraph would need to be in order to be included
+in the list item.
 
 So, in this case we need two spaces indent:
 
@@ -5049,11 +5134,9 @@ item:
  - b
   - c
    - d
-    - e
+  - e
-   - f
+ - f
-  - g
+- g
- - h
-- i
 .
 <ul>
 <li>a</li>
@@ -5063,8 +5146,6 @@ item:
 <li>e</li>
 <li>f</li>
 <li>g</li>
-<li>h</li>
-<li>i</li>
 </ul>
 ````````````````````````````````
 
@@ -5074,7 +5155,7 @@ item:
 
   2. b
 
-    3. c
+   3. c
 .
 <ol>
 <li>
@@ -5089,6 +5170,49 @@ item:
 </ol>
 ````````````````````````````````
 
+Note, however, that list items may not be indented more than
+three spaces.  Here `- e` is treated as a paragraph continuation
+line, because it is indented more than three spaces:
+
+```````````````````````````````` example
+- a
+ - b
+  - c
+   - d
+    - e
+.
+<ul>
+<li>a</li>
+<li>b</li>
+<li>c</li>
+<li>d
+- e</li>
+</ul>
+````````````````````````````````
+
+And here, `3. c` is treated as in indented code block,
+because it is indented four spaces and preceded by a
+blank line.
+
+```````````````````````````````` example
+1. a
+
+  2. b
+
+    3. c
+.
+<ol>
+<li>
+<p>a</p>
+</li>
+<li>
+<p>b</p>
+</li>
+</ol>
+<pre><code>3. c
+</code></pre>
+````````````````````````````````
+
 
 This is a loose list, because there is a blank line between
 two of the list items:
@@ -5378,10 +5502,10 @@ Thus, for example, in
 <p><code>hi</code>lo`</p>
 ````````````````````````````````
 
-
 `hi` is parsed as code, leaving the backtick at the end as a literal
 backtick.
 
+
 ## Backslash escapes
 
 Any ASCII punctuation character may be backslash-escaped:
@@ -5415,6 +5539,7 @@ not have their usual Markdown meanings:
 \* not a list
 \# not a heading
 \[foo]: /url "not a reference"
+\&ouml; not a character entity
 .
 <p>*not emphasized*
 &lt;br/&gt; not a tag
@@ -5423,7 +5548,8 @@ not have their usual Markdown meanings:
 1. not a list
 * not a list
 # not a heading
-[foo]: /url &quot;not a reference&quot;</p>
+[foo]: /url &quot;not a reference&quot;
+&amp;ouml; not a character entity</p>
 ````````````````````````````````
 
 
@@ -5521,13 +5647,23 @@ foo
 
 ## Entity and numeric character references
 
-All valid HTML entity references and numeric character
+Valid HTML entity references and numeric character references
-references, except those occuring in code blocks and code spans,
+can be used in place of the corresponding Unicode character,
-are recognized as such and treated as equivalent to the
+with the following exceptions:
-corresponding Unicode characters.  Conforming CommonMark parsers
+
-need not store information about whether a particular character
+- Entity and character references are not recognized in code
-was represented in the source using a Unicode character or
+  blocks and code spans.
-an entity reference.
+
+- Entity and character references cannot stand in place of
+  special characters that define structural elements in
+  CommonMark.  For example, although `&#42;` can be used
+  in place of a literal `*` character, `&#42;` cannot replace
+  `*` in emphasis delimiters, bullet list markers, or thematic
+  breaks.
+
+Conforming CommonMark parsers need not store information about
+whether a particular character was represented in the source
+using a Unicode character or an entity reference.
 
 [Entity references](@) consist of `&` + any of the valid
 HTML5 entity names + `;`. The
@@ -5548,22 +5684,22 @@ references and their corresponding code points.
 
 [Decimal numeric character
 references](@)
-consist of `&#` + a string of 1--8 arabic digits + `;`. A
+consist of `&#` + a string of 1--7 arabic digits + `;`. A
 numeric character reference is parsed as the corresponding
 Unicode character. Invalid Unicode code points will be replaced by
 the REPLACEMENT CHARACTER (`U+FFFD`).  For security reasons,
 the code point `U+0000` will also be replaced by `U+FFFD`.
 
 ```````````````````````````````` example
-&#35; &#1234; &#992; &#98765432; &#0;
+&#35; &#1234; &#992; &#0;
 .
-<p># Ӓ Ϡ � �</p>
+<p># Ӓ Ϡ �</p>
 ````````````````````````````````
 
 
 [Hexadecimal numeric character
 references](@) consist of `&#` +
-either `X` or `x` + a string of 1-8 hexadecimal digits + `;`.
+either `X` or `x` + a string of 1-6 hexadecimal digits + `;`.
 They too are parsed as the corresponding Unicode character (this
 time specified with a hexadecimal numeral instead of decimal).
 
@@ -5578,9 +5714,13 @@ Here are some nonentities:
 
 ```````````````````````````````` example
 &nbsp &x; &#; &#x;
+&#987654321;
+&#abcdef0;
 &ThisIsNotDefined; &hi?;
 .
 <p>&amp;nbsp &amp;x; &amp;#; &amp;#x;
+&amp;#987654321;
+&amp;#abcdef0;
 &amp;ThisIsNotDefined; &amp;hi?;</p>
 ````````````````````````````````
 
@@ -5661,6 +5801,51 @@ text in code spans and code blocks:
 ````````````````````````````````
 
 
+Entity and numeric character references cannot be used
+in place of symbols indicating structure in CommonMark
+documents.
+
+```````````````````````````````` example
+&#42;foo&#42;
+*foo*
+.
+<p>*foo*
+<em>foo</em></p>
+````````````````````````````````
+
+```````````````````````````````` example
+&#42; foo
+
+* foo
+.
+<p>* foo</p>
+<ul>
+<li>foo</li>
+</ul>
+````````````````````````````````
+
+```````````````````````````````` example
+foo&#10;&#10;bar
+.
+<p>foo
+
+bar</p>
+````````````````````````````````
+
+```````````````````````````````` example
+&#9;foo
+.
+<p>→foo</p>
+````````````````````````````````
+
+
+```````````````````````````````` example
+[a](url &quot;tit&quot;)
+.
+<p>[a](url &quot;tit&quot;)</p>
+````````````````````````````````
+
+
 ## Code spans
 
 A [backtick string](@)
@@ -5669,9 +5854,16 @@ preceded nor followed by a backtick.
 
 A [code span](@) begins with a backtick string and ends with
 a backtick string of equal length.  The contents of the code span are
-the characters between the two backtick strings, with leading and
+the characters between the two backtick strings, normalized in the
-trailing spaces and [line endings] removed, and
+following ways:
-[whitespace] collapsed to single spaces.
+
+- First, [line endings] are converted to [spaces].
+- If the resulting string both begins *and* ends with a [space]
+  character, but does not consist entirely of [space]
+  characters, a single [space] character is removed from the
+  front and back.  This allows you to include code that begins
+  or ends with backtick characters, which must be separated by
+  whitespace from the opening or closing backtick strings.
 
 This is a simple code span:
 
@@ -5683,10 +5875,11 @@ This is a simple code span:
 
 
 Here two backticks are used, because the code contains a backtick.
-This example also illustrates stripping of leading and trailing spaces:
+This example also illustrates stripping of a single leading and
+trailing space:
 
 ```````````````````````````````` example
-`` foo ` bar  ``
+`` foo ` bar ``
 .
 <p><code>foo ` bar</code></p>
 ````````````````````````````````
@@ -5701,58 +5894,79 @@ spaces:
 <p><code>``</code></p>
 ````````````````````````````````
 
+Note that only *one* space is stripped:
 
-[Line endings] are treated like spaces:
+```````````````````````````````` example
+`  ``  `
+.
+<p><code> `` </code></p>
+````````````````````````````````
+
+The stripping only happens if the space is on both
+sides of the string:
 
 ```````````````````````````````` example
-``
+` a`
-foo
-``
 .
-<p><code>foo</code></p>
+<p><code> a</code></p>
 ````````````````````````````````
 
+Only [spaces], and not [unicode whitespace] in general, are
+stripped in this way:
+
+```````````````````````````````` example
+` b `
+.
+<p><code> b </code></p>
+````````````````````````````````
 
-Interior spaces and [line endings] are collapsed into
+No stripping occurs if the code span contains only spaces:
-single spaces, just as they would be by a browser:
 
 ```````````````````````````````` example
-`foo   bar
+` `
-  baz`
+`  `
 .
-<p><code>foo bar baz</code></p>
+<p><code> </code>
+<code>  </code></p>
 ````````````````````````````````
 
 
-Not all [Unicode whitespace] (for instance, non-breaking space) is
+[Line endings] are treated like spaces:
-collapsed, however:
 
 ```````````````````````````````` example
-`a  b`
+``
+foo
+bar  
+baz
+``
 .
-<p><code>a  b</code></p>
+<p><code>foo bar   baz</code></p>
 ````````````````````````````````
 
+```````````````````````````````` example
+``
+foo 
+``
+.
+<p><code>foo </code></p>
+````````````````````````````````
 
-Q: Why not just leave the spaces, since browsers will collapse them
-anyway?  A:  Because we might be targeting a non-HTML format, and we
-shouldn't rely on HTML-specific rendering assumptions.
 
-(Existing implementations differ in their treatment of internal
+Interior spaces are not collapsed:
-spaces and [line endings].  Some, including `Markdown.pl` and
-`showdown`, convert an internal [line ending] into a
-`<br />` tag.  But this makes things difficult for those who like to
-hard-wrap their paragraphs, since a line break in the midst of a code
-span will cause an unintended line break in the output.  Others just
-leave internal spaces as they are, which is fine if only HTML is being
-targeted.)
 
 ```````````````````````````````` example
-`foo `` bar`
+`foo   bar 
+baz`
 .
-<p><code>foo `` bar</code></p>
+<p><code>foo   bar  baz</code></p>
 ````````````````````````````````
 
+Note that browsers will typically collapse consecutive spaces
+when rendering `<code>` elements, so it is recommended that
+the following CSS be used:
+
+    code{white-space: pre-wrap;}
+
 
 Note that backslash escapes do not work in code spans. All backslashes
 are treated literally:
@@ -5768,6 +5982,19 @@ Backslash escapes are never needed, because one can always choose a
 string of *n* backtick characters as delimiters, where the code does
 not contain any strings of exactly *n* backtick characters.
 
+```````````````````````````````` example
+``foo`bar``
+.
+<p><code>foo`bar</code></p>
+````````````````````````````````
+
+```````````````````````````````` example
+` foo `` bar `
+.
+<p><code>foo `` bar</code></p>
+````````````````````````````````
+
+
 Code span backticks have higher precedence than any other inline
 constructs except HTML tags and autolinks.  Thus, for example, this is
 not parsed as emphasized text, since the second `*` is part of a code
@@ -5905,15 +6132,17 @@ of one or more `_` characters that is not preceded or followed by
 a non-backslash-escaped `_` character.
 
 A [left-flanking delimiter run](@) is
-a [delimiter run] that is (a) not followed by [Unicode whitespace],
+a [delimiter run] that is (1) not followed by [Unicode whitespace],
-and (b) not followed by a [punctuation character], or
+and either (2a) not followed by a [punctuation character], or
+(2b) followed by a [punctuation character] and
 preceded by [Unicode whitespace] or a [punctuation character].
 For purposes of this definition, the beginning and the end of
 the line count as Unicode whitespace.
 
 A [right-flanking delimiter run](@) is
-a [delimiter run] that is (a) not preceded by [Unicode whitespace],
+a [delimiter run] that is (1) not preceded by [Unicode whitespace],
-and (b) not preceded by a [punctuation character], or
+and either (2a) not preceded by a [punctuation character], or
+(2b) preceded by a [punctuation character] and
 followed by [Unicode whitespace] or a [punctuation character].
 For purposes of this definition, the beginning and the end of
 the line count as Unicode whitespace.
@@ -6005,7 +6234,8 @@ The following rules define emphasis and strong emphasis:
     [delimiter runs].  If one of the delimiters can both
     open and close emphasis, then the sum of the lengths of the
     delimiter runs containing the opening and closing delimiters
-    must not be a multiple of 3.
+    must not be a multiple of 3 unless both lengths are
+    multiples of 3.
 
 10. Strong emphasis begins with a delimiter that
     [can open strong emphasis] and ends with a delimiter that
@@ -6015,7 +6245,8 @@ The following rules define emphasis and strong emphasis:
     [delimiter runs].  If one of the delimiters can both open
     and close strong emphasis, then the sum of the lengths of
     the delimiter runs containing the opening and closing
-    delimiters must not be a multiple of 3.
+    delimiters must not be a multiple of 3 unless both lengths
+    are multiples of 3.
 
 11. A literal `*` character cannot occur at the beginning or end of
     `*`-delimited emphasis or `**`-delimited strong emphasis, unless it
@@ -6634,7 +6865,19 @@ is precluded by the condition that a delimiter that
 can both open and close (like the `*` after `foo`)
 cannot form emphasis if the sum of the lengths of
 the delimiter runs containing the opening and
-closing delimiters is a multiple of 3.
+closing delimiters is a multiple of 3 unless
+both lengths are multiples of 3.
+
+
+For the same reason, we don't get two consecutive
+emphasis sections in this example:
+
+```````````````````````````````` example
+*foo**bar*
+.
+<p><em>foo**bar</em></p>
+````````````````````````````````
+
 
 The same condition ensures that the following
 cases are all strong emphasis nested inside
@@ -6663,6 +6906,23 @@ omitted:
 ````````````````````````````````
 
 
+When the lengths of the interior closing and opening
+delimiter runs are *both* multiples of 3, though,
+they can match to create emphasis:
+
+```````````````````````````````` example
+foo***bar***baz
+.
+<p>foo<em><strong>bar</strong></em>baz</p>
+````````````````````````````````
+
+```````````````````````````````` example
+foo******bar*********baz
+.
+<p>foo<strong><strong><strong>bar</strong></strong></strong>***baz</p>
+````````````````````````````````
+
+
 Indefinite levels of nesting are possible:
 
 ```````````````````````````````` example
@@ -7198,15 +7458,16 @@ following rules apply:
 A [link destination](@) consists of either
 
 - a sequence of zero or more characters between an opening `<` and a
-  closing `>` that contains no spaces, line breaks, or unescaped
+  closing `>` that contains no line breaks or unescaped
   `<` or `>` characters, or
 
-- a nonempty sequence of characters that does not include
+- a nonempty sequence of characters that does not start with
-  ASCII space or control characters, and includes parentheses
+  `<`, does not include ASCII space or control characters, and
-  only if (a) they are backslash-escaped or (b) they are part of
+  includes parentheses only if (a) they are backslash-escaped or
-  a balanced pair of unescaped parentheses.  (Implementations
+  (b) they are part of a balanced pair of unescaped parentheses.
-  may impose limits on parentheses nesting to avoid performance
+  (Implementations may impose limits on parentheses nesting to
-  issues, but at least three levels of nesting should be supported.)
+  avoid performance issues, but at least three levels of nesting
+  should be supported.)
 
 A [link title](@)  consists of either
 
@@ -7219,7 +7480,8 @@ A [link title](@)  consists of either
   backslash-escaped, or
 
 - a sequence of zero or more characters between matching parentheses
-  (`(...)`), including a `)` character only if it is backslash-escaped.
+  (`(...)`), including a `(` or `)` character only if it is
+  backslash-escaped.
 
 Although [link titles] may span multiple lines, they may not contain
 a [blank line].
@@ -7269,9 +7531,8 @@ Both the title and the destination may be omitted:
 <p><a href="">link</a></p>
 ````````````````````````````````
 
-
+The destination can only contain spaces if it is
-The destination cannot contain spaces or line breaks,
+enclosed in pointy brackets:
-even if enclosed in pointy brackets:
 
 ```````````````````````````````` example
 [link](/my uri)
@@ -7279,13 +7540,14 @@ even if enclosed in pointy brackets:
 <p>[link](/my uri)</p>
 ````````````````````````````````
 
-
 ```````````````````````````````` example
 [link](</my uri>)
 .
-<p>[link](&lt;/my uri&gt;)</p>
+<p><a href="/my%20uri">link</a></p>
 ````````````````````````````````
 
+The destination cannot contain line breaks,
+even if enclosed in pointy brackets:
 
 ```````````````````````````````` example
 [link](foo
@@ -7295,7 +7557,6 @@ bar)
 bar)</p>
 ````````````````````````````````
 
-
 ```````````````````````````````` example
 [link](<foo
 bar>)
@@ -7304,6 +7565,36 @@ bar>)
 bar>)</p>
 ````````````````````````````````
 
+The destination can contain `)` if it is enclosed
+in pointy brackets:
+
+```````````````````````````````` example
+[a](<b)c>)
+.
+<p><a href="b)c">a</a></p>
+````````````````````````````````
+
+Pointy brackets that enclose links must be unescaped:
+
+```````````````````````````````` example
+[link](<foo\>)
+.
+<p>[link](&lt;foo&gt;)</p>
+````````````````````````````````
+
+These are not links, because the opening pointy bracket
+is not matched properly:
+
+```````````````````````````````` example
+[a](<b)c
+[a](<b)c>
+[a](<b>c)
+.
+<p>[a](&lt;b)c
+[a](&lt;b)c&gt;
+[a](<b>c)</p>
+````````````````````````````````
+
 Parentheses inside the link destination may be escaped:
 
 ```````````````````````````````` example
@@ -8411,7 +8702,7 @@ If you want a link after a literal `!`, backslash-escape the
 as the link label.
 
 A [URI autolink](@) consists of `<`, followed by an
-[absolute URI] not containing `<`, followed by `>`.  It is parsed as
+[absolute URI] followed by `>`.  It is parsed as
 a link to the URI, with the URI as the link's label.
 
 An [absolute URI](@),
@@ -8624,7 +8915,7 @@ a [single-quoted attribute value], or a [double-quoted attribute value].
 
 An [unquoted attribute value](@)
 is a nonempty string of characters not
-including spaces, `"`, `'`, `=`, `<`, `>`, or `` ` ``.
+including [whitespace], `"`, `'`, `=`, `<`, `>`, or `` ` ``.
 
 A [single-quoted attribute value](@)
 consists of `'`, zero or more
@@ -8745,9 +9036,13 @@ Illegal [whitespace]:
 ```````````````````````````````` example
 < a><
 foo><bar/ >
+<foo bar=baz
+bim!bop />
 .
 <p>&lt; a&gt;&lt;
-foo&gt;&lt;bar/ &gt;</p>
+foo&gt;&lt;bar/ &gt;
+&lt;foo bar=baz
+bim!bop /&gt;</p>
 ````````````````````````````````
 
 
@@ -8944,10 +9239,10 @@ bar</em></p>
 Line breaks do not occur inside code spans
 
 ```````````````````````````````` example
-`code  
+`code 
 span`
 .
-<p><code>code span</code></p>
+<p><code>code  span</code></p>
 ````````````````````````````````
 
 
@@ -9365,7 +9660,8 @@ just above `stack_bottom` (or the first element if `stack_bottom`
 is NULL).
 
 We keep track of the `openers_bottom` for each delimiter
-type (`*`, `_`).  Initialize this to `stack_bottom`.
+type (`*`, `_`) and each length of the closing delimiter run
+(modulo 3).  Initialize this to `stack_bottom`.
 
 Then we repeat the following until we run out of potential
 closers:
@@ -9397,7 +9693,7 @@ closers:
     of the delimiter stack.  If the closing node is removed, reset
     `current_position` to the next element in the stack.
 
-- If none in found:
+- If none is found:
 
   + Set `openers_bottom` to the element before `current_position`.
     (We know that there are no openers for this kind of closer up to and