handle app store url scheme

[jdanyow]

saw this in the chat: https://parcel-bundler.slack.com/archives/C8B26V8RF/p1514579681000034

[leonardosnt]

Related: #437

Why not use /^[\w-+.]*:/i ? (or ^[a-z][\w-+.]*:) It will handle more use cases.

The scheme, consisting of a sequence of characters beginning with a letter and followed by any combination of letters, digits, plus (+), period (.), or hyphen (-)

https://en.wikipedia.org/wiki/Uniform_Resource_Identifier#Syntax

[hkwid]

According to here https://www.iana.org/assignments/uri-schemes/uri-schemes.xhtml
URI schema can include numbers like z39.50.

How about /^[a-z][a-z0-9\+-\.]*:/i /^[a-z][a-z0-9\-+.]*:/i for SCHEME_REGEXP?

(Inside character classes: only ^-]\ are needed to escape
reference: https://stackoverflow.com/questions/399078/what-special-characters-must-be-escaped-in-regular-expressions#answer-400316)

BTW, for integration test, we can add <a href="itms-apps://...">App Store Link</a> to test/integration/html/index.html

...
  <a href="tel:+33636757575">Tel link</a>
  <a href="itms-apps://itunes.apple.com/en/app/awesomeApp/id1234567890">App Store Link</a>
  <script src="index.js"></script>
...

[leonardosnt]

\w already cover alphanumeric (a-z0-9)

https://regexr.com/3ik67

[hkwid]

@leonardosnt I guess \w is included A-Z too. URI schema seems like must be lowercase.

Although schemes are case-insensitive, the canonical form is lowercase and documents that specify schemes must do so with lowercase letters. It is followed by a colon (:). Examples of popular schemes include http(s), ftp, mailto, file, data, and irc. URI schemes should be registered with the Internet Assigned Numbers Authority (IANA), although non-registered schemes are used in practice.
https://en.wikipedia.org/wiki/Uniform_Resource_Identifier#Syntax

[leonardosnt]

Yeah, you are right. \w also includes underscore, a-z0-9 is better!

[devongovett]

updated the regex a bit based on suggestions in the comments. thanks!