GFM enables the autolink extension, where autolinks will be recognised in a
greater number of conditions.
[Autolink]s can also be constructed without requiring the use of < and to >
to delimit them, although they will be recognized under a smaller set of
circumstances. All such recognized autolinks can only come at the beginning of
a line, after whitespace, or any of the delimiting characters *, _, ~,
and (.
An extended www autolink will be recognized when the text www. is found
followed by a [valid domain]. A valid domain consists of alphanumeric
characters, underscores (_), hyphens (-) and periods (.). There must be
at least one period, and no underscores may be present in the last two segments
of the domain.
The scheme http will be inserted automatically:
www.commonmark.org
.
<p><a href="http://www.commonmark.org">www.commonmark.org</a></p>
After a [valid domain], zero or more non-space non-< characters may follow:
Visit www.commonmark.org/help for more information.
.
<p>Visit <a href="http://www.commonmark.org/help">www.commonmark.org/help</a> for more information.</p>
We then apply extended autolink path validation as follows:
Trailing punctuation (specifically, ?, !, ., ,, :, *, _, and ~)
will not be considered part of the autolink, though they may be included in the
interior of the link:
Visit www.commonmark.org.
Visit www.commonmark.org/a.b.
Visit www.commonmark.org/~jm/foo/bar.pdf.
.
<p>Visit <a href="http://www.commonmark.org">www.commonmark.org</a>.</p>
<p>Visit <a href="http://www.commonmark.org/a.b">www.commonmark.org/a.b</a>.</p>
<p>Visit <a href="http://www.commonmark.org/~jm/foo/bar.pdf">www.commonmark.org/~jm/foo/bar.pdf</a>.</p>
((commonmark-hs: We depart from the GFM spec here. Alternative spec and tests can be found after these commented-out ones. For motivation for this departure from the GFM spec, see #147.))
When an autolink ends in
), we scan the entire autolink for the total number of parentheses. If there is a greater number of closing parentheses than opening ones, we don't consider the last character part of the autolink, in order to facilitate including an autolink inside a parenthesis:www.google.com/search?q=Markup+(business) (www.google.com/search?q=Markup+(business)) . <p><a href="http://www.google.com/search?q=Markup+(business)">www.google.com/search?q=Markup+(business)</a></p> <p>(<a href="http://www.google.com/search?q=Markup+(business)">www.google.com/search?q=Markup+(business)</a>)</p>This check is only done when the link ends in a closing parentheses
), so if the only parentheses are in the interior of the autolink, no special rules are applied:www.google.com/search?q=(business))+ok . <p><a href="http://www.google.com/search?q=(business))+ok">www.google.com/search?q=(business))+ok</a></p>
Autolinks can contain balanced pairs of parentheses, or unbalanced ).
We don't allow unbalanced ), in order to facilitate including
an autolink inside a parenthesis:
www.google.com/search?q=Markup+(business)
(www.google.com/search?q=Markup+(business))
.
<p><a href="http://www.google.com/search?q=Markup+(business)">www.google.com/search?q=Markup+(business)</a></p>
<p>(<a href="http://www.google.com/search?q=Markup+(business)">www.google.com/search?q=Markup+(business)</a>)</p>
Issue #147:
[link](https://baidu.com)aaa<span></span>bbb
.
<p><a href="https://baidu.com">link</a>aaa<span></span>bbb</p>
((End of diverging section.))
If an autolink ends in a semicolon (;), we check to see if it appears to
resemble an [entity reference][entity references]; if the preceding text is &
followed by one or more alphanumeric characters. If so, it is excluded from
the autolink:
www.google.com/search?q=commonmark&hl=en
www.google.com/search?q=commonmark&hl;
.
<p><a href="http://www.google.com/search?q=commonmark&hl=en">www.google.com/search?q=commonmark&hl=en</a></p>
<p><a href="http://www.google.com/search?q=commonmark">www.google.com/search?q=commonmark</a>&hl;</p>
< immediately ends an autolink.
www.commonmark.org/he<lp
.
<p><a href="http://www.commonmark.org/he">www.commonmark.org/he</a><lp</p>
An extended url autolink will be recognised when one of the schemes
http://, https://, or ftp://, followed by a [valid domain], then zero or
more non-space non-< characters according to
[extended autolink path validation]:
http://commonmark.org
(Visit https://encrypted.google.com/search?q=Markup+(business))
Anonymous FTP is available at ftp://foo.bar.baz.
.
<p><a href="http://commonmark.org">http://commonmark.org</a></p>
<p>(Visit <a href="https://encrypted.google.com/search?q=Markup+(business)">https://encrypted.google.com/search?q=Markup+(business)</a>)</p>
<p>Anonymous FTP is available at <a href="ftp://foo.bar.baz">ftp://foo.bar.baz</a>.</p>
An extended email autolink will be recognised when an email address is recognised within any text node. Email addresses are recognised according to the following rules:
- One ore more characters which are alphanumeric, or
.,-,_, or+. - An
@symbol. - One or more characters which are alphanumeric, or
.,-, or_. At least one of the characters here must be a period (.). The last character must not be one of-or_. If the last character is a period (.), it will be excluded from the autolink.
The scheme mailto: will automatically be added to the generated link:
[email protected]
.
<p><a href="mailto:[email protected]">[email protected]</a></p>
+ can occur before the @, but not after.
hello@mail+xyz.example isn't valid, but [email protected] is.
.
<p>hello@mail+xyz.example isn't valid, but <a href="mailto:[email protected]">[email protected]</a> is.</p>
., -, and _ can occur on both sides of the @, but only . may occur at
the end of the email address, in which case it will not be considered part of
the address:
[email protected]
[email protected].
[email protected]
[email protected]_
.
<p><a href="mailto:[email protected]">[email protected]</a></p>
<p><a href="mailto:[email protected]">[email protected]</a>.</p>
<p>[email protected]</p>
<p>[email protected]_</p>
The autolinks extension should not interfere with regular links (#65).
[a link](http://www.google.com/)stuff?
.
<p><a href="http://www.google.com/">a link</a>stuff?</p>
Autolinks with punctuation (#151):
https://en.wikipedia.org/wiki/St._Petersburg_paradox
https://en.wikipedia.org/wiki/Liaison_(French)
https://en.wikipedia.org/wiki/Frederick_III,_German_Emperor
.
<p><a href="https://en.wikipedia.org/wiki/St._Petersburg_paradox">https://en.wikipedia.org/wiki/St._Petersburg_paradox</a></p>
<p><a href="https://en.wikipedia.org/wiki/Liaison_(French)">https://en.wikipedia.org/wiki/Liaison_(French)</a></p>
<p><a href="https://en.wikipedia.org/wiki/Frederick_III,_German_Emperor">https://en.wikipedia.org/wiki/Frederick_III,_German_Emperor</a></p>