Emoji sequences with ZERO WIDTH JOINER counted as separate chars when they probably shouldn't

[p6rt]

Migrated from rt.perl.org#127048 (status was 'resolved')

Searchable as RT127048$

[p6rt]

From @AlexDaniel

This is a continuation of
https://rt.perl.org/Public/Bug/Display.html?id=127047

From http://unicode.org/reports/tr51/#Emoji_ZWJ_Sequences​:

“The U+200D ZERO WIDTH JOINER (ZWJ) can be used between the elements of a
sequence of characters to indicate that a single glyph should be presented
if available.”

“So to the user, these would behave like single emoji characters, even
though internally they are sequences.”

It sounds like we shouldn't cut these sequences in half when doing .substr
(which in turn means that these should be treated as one grapheme).

There is a chart of possible combinations here
http://www.unicode.org/emoji/charts/emoji-zwj-sequences.html, but I think
that any sequence with U+200D ZERO WIDTH JOINER should probably result in
one grapheme. As crazy as it sounds…

[p6rt]

From @AlexDaniel

It should also be noted that ZERO WIDTH JOINER is used for other purposes
too​:
https://books.google.ee/books?id=wn5sXG8bEAcC&lpg=PA287&ots=J1bym1VbXE&dq=unicode%20%22ZERO%20WIDTH%20JOINER&pg=PA287#v=onepage&q=unicode%20%22ZERO%20WIDTH%20JOINER&f=false

But I'm not sure if it should affect the character count in such cases.

[p6rt]

From @samcv

This has been resolved since a month or so ago. This was closed with this commit​:
MoarVM/MoarVM@fa5158a

[p6rt]

@samcv - Status changed from 'new' to 'resolved'