Possible bug in URI::MailTo::EMAIL_REGEXP when parsing emails addresses containing two consecutive dots

[lucianghinda]

If the following email address is invalid:

thing..something.else@example.com

Then the URI::MailTo::EMAIL_REGEXP is allowing it, and it should not.

Example:

URI::MailTo::EMAIL_REGEXP.match?('thing..something.else@example.com') 

Should return false.

I interpret the section 3.41 from https://www.ietf.org/rfc/rfc5322.txt says:

If the string can be represented as a dot-atom (that is, it contains no
characters other than atext characters or "." surrounded by atext
characters),

That to me says that the part before @ can be formed by a string or a dot and a string, and since that string cannot be empty, that means there cannot be two consecutive dots.

[y-yagi]

I think this issue is fixed by #172.

[hsbt]

I released v1.1.0 with #172. Could you try it for your issue? Thanks!

[sorah]

Quickly informing that I've reverted #172 at #189 and shipped v1.1.1 as the email addresses in question were intentionally allowed - it is based on WHATWG's practical pattern, contains intentional violation against RFCs. It was mentioned in a comment but unfortunate it lacked test cases. There is a room to add RFC-strict regexp pattern under another *_REGEXP constant, but changing behaviour of the existing constant considered a bug or regression. If you need such strict patterns, please file a feature request instead.

uri/lib/uri/mailto.rb

Lines 53 to 55 in f1b05c8

	# practical regexp for email address
	# https://html.spec.whatwg.org/multipage/input.html#valid-e-mail-address
	EMAIL_REGEXP = /\A[a-zA-Z0-9.!\#$%&'*+\/=?^_`{|}~-]+@[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*\z/