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permissive-www-autolinks.txt (3631B)
1
2 # Permissive WWW Autolinks
3
4 With the flag `MD_FLAG_PERMISSIVEWWWAUTOLINKS`, MD4C enables recognition of
5 autolinks starting with `www.`, even if they do not exactly follow the syntax
6 of autolink as specified in CommonMark specification.
7
8 These do not have to be enclosed in `<` and `>`, and they even do not need
9 any preceding scheme specification.
10
11 The WWW autolink will be recognized when a valid domain is found.
12
13 A valid domain consists of the text `www.`, followed by alphanumeric characters,
14 nderscores (`_`), hyphens (`-`) and periods (`.`). There must be at least one
15 period, and no underscores may be present in the last two segments of the domain.
16
17 The scheme `http` will be inserted automatically:
18
19 ```````````````````````````````` example
20 www.commonmark.org
21 .
22 <p><a href="http://www.commonmark.org">www.commonmark.org</a></p>
23 ````````````````````````````````
24
25 After a valid domain, zero or more non-space non-`<` characters may follow:
26
27 ```````````````````````````````` example
28 Visit www.commonmark.org/help for more information.
29 .
30 <p>Visit <a href="http://www.commonmark.org/help">www.commonmark.org/help</a> for more information.</p>
31 ````````````````````````````````
32
33 We then apply extended autolink path validation as follows:
34
35 Trailing punctuation (specifically, `?`, `!`, `.`, `,`, `:`, `*`, `_`, and `~`)
36 will not be considered part of the autolink, though they may be included in the
37 interior of the link:
38
39 ```````````````````````````````` example
40 Visit www.commonmark.org.
41
42 Visit www.commonmark.org/a.b.
43 .
44 <p>Visit <a href="http://www.commonmark.org">www.commonmark.org</a>.</p>
45 <p>Visit <a href="http://www.commonmark.org/a.b">www.commonmark.org/a.b</a>.</p>
46 ````````````````````````````````
47
48 When an autolink ends in `)`, we scan the entire autolink for the total number
49 of parentheses. If there is a greater number of closing parentheses than
50 opening ones, we don't consider the last character part of the autolink, in
51 order to facilitate including an autolink inside a parenthesis:
52
53 ```````````````````````````````` example
54 www.google.com/search?q=Markup+(business)
55
56 (www.google.com/search?q=Markup+(business))
57 .
58 <p><a href="http://www.google.com/search?q=Markup+(business)">www.google.com/search?q=Markup+(business)</a></p>
59 <p>(<a href="http://www.google.com/search?q=Markup+(business)">www.google.com/search?q=Markup+(business)</a>)</p>
60 ````````````````````````````````
61
62 This check is only done when the link ends in a closing parentheses `)`, so if
63 the only parentheses are in the interior of the autolink, no special rules are
64 applied:
65
66 ```````````````````````````````` example
67 www.google.com/search?q=(business))+ok
68 .
69 <p><a href="http://www.google.com/search?q=(business))+ok">www.google.com/search?q=(business))+ok</a></p>
70 ````````````````````````````````
71
72 If an autolink ends in a semicolon (`;`), we check to see if it appears to
73 resemble an [entity reference][entity references]; if the preceding text is `&`
74 followed by one or more alphanumeric characters. If so, it is excluded from
75 the autolink:
76
77 ```````````````````````````````` example
78 www.google.com/search?q=commonmark&hl=en
79
80 www.google.com/search?q=commonmark&hl;
81 .
82 <p><a href="http://www.google.com/search?q=commonmark&hl=en">www.google.com/search?q=commonmark&hl=en</a></p>
83 <p><a href="http://www.google.com/search?q=commonmark">www.google.com/search?q=commonmark</a>&hl;</p>
84 ````````````````````````````````
85
86 `<` immediately ends an autolink.
87
88 ```````````````````````````````` example
89 www.commonmark.org/he<lp
90 .
91 <p><a href="http://www.commonmark.org/he">www.commonmark.org/he</a><lp</p>
92 ````````````````````````````````