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