Subject: bug#27403: 26.0.50; Indentation misalignment with Unicode code points >65535

From: Adam Niederer <[email-masked]>
Date: Sat, 17 Jun 2017 02:28:41 -0400

Hello, I believe I've found an indentation issue. To reproduce, start
emacs, create a buffer in js-mode, paste in this code, and press C-x h
TAB to indent the buffer:

let x = /* 👍 */ { foo: 0
                   bar: 0 }

let x = /* ☺ */ { foo: 0
                  bar: 0 }

Both 25.2 and 26.0.50 add one extra space before "bar" in the first
first snippet with U+1F44D THUMBS UP SIGN in the comment, whereas the
second snippet with U+263A WHITE SMILING FACE properly aligns "bar" with
"foo". This appears to happen whenever the character in the comment
needs a surrogate pair.

This issue also happens in python-mode:

"👍", {"a": 2,
       "b": 3}

"☺", {"a":2,
      "b":3}

Interestingly, pressing TAB with one's point on the second line of each
snippet to dedent the line yields a correct result for both symbols:

"👍", {"a": 2,
    "b": 3}

"☺", {"a":2,
    "b":3}

Just in case those Emoji don't make it through the mail properly, the
first snippet in each example contains U+1F44D THUMBS UP SIGN before
the map, and the second snippet contains U+263A WHITE SMILING FACE.

-Adam

In GNU Emacs 26.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.22.15)
of 2017-06-17 built on AdamsPC
Repository revision: 49c0ff29c2e0243ba35ec17e3e3af49369be43db
Windowing system distributor 'The X.Org Foundation', version 11.0.11903000
System Description: Arch Linux

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