GNU bug report logs - #48043
UTF-8 magic comment is unwelcome with recent Ruby versions

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Peter Oliver <p.d.oliver <at> mavit.org.uk>
To: bug-gnu-emacs <at> gnu.org
Subject: UTF-8 magic comment is unwelcome with recent Ruby versions
Date: Mon, 26 Apr 2021 19:28:21 +0100 (BST)

[Message part 1 (text/plain, inline)]

When saving a ruby-mode buffer, if the content is not plain ASCII, then the default behaviour is to add a specially-formatted comment that indicates the encoding to the Ruby interpreter.  E.g.,

# coding: utf-8

However, since Ruby 2.0 released in 2013, the default encoding for Ruby has been UTF-8.  Consequently, users of other editors tend not to include this comment when using UTF-8.  When you edit such a file with Emacs, you end up with a messy diff.

Two patches are attached to address this:

- The first patch adds a new choice to ruby-insert-encoding-magic-comment, unless-utf8, which causes the magic comment not to be inserted if the encoding is UTF-8.

- The second patch, perhaps more controversially, makes this the default.

-- 
Peter Oliver

[0001-New-choice-for-ruby-insert-encoding-magic-comment-un.patch (text/plain, attachment)]

[0002-Default-ruby-insert-encoding-magic-comment-to-unless.patch (text/plain, attachment)]

Message #8 received at 48043 <at> debbugs.gnu.org (full text, mbox):

From: Dmitry Gutov <dgutov <at> yandex.ru>
To: Peter Oliver <p.d.oliver <at> mavit.org.uk>, 48043 <at> debbugs.gnu.org
Subject: Re: bug#48043: UTF-8 magic comment is unwelcome with recent Ruby
 versions
Date: Tue, 27 Apr 2021 00:04:58 +0300

Hi!

On 26.04.2021 21:28, Peter Oliver wrote:
> When saving a ruby-mode buffer, if the content is not plain ASCII, then 
> the default behaviour is to add a specially-formatted comment that 
> indicates the encoding to the Ruby interpreter.  E.g.,
> 
> # coding: utf-8
> 
> However, since Ruby 2.0 released in 2013, the default encoding for Ruby 
> has been UTF-8.  Consequently, users of other editors tend not to 
> include this comment when using UTF-8.  When you edit such a file with 
> Emacs, you end up with a messy diff.
> 
> Two patches are attached to address this:
> 
> - The first patch adds a new choice to 
> ruby-insert-encoding-magic-comment, unless-utf8, which causes the magic 
> comment not to be inserted if the encoding is UTF-8.
> 
> - The second patch, perhaps more controversially, makes this the default.

Both changes make sense to me.

However, I've looked at the existing code and found a prior change which 
intended for this to be more customizable already, yet had a minor bug.

Please try out the following patch:

diff --git a/lisp/progmodes/ruby-mode.el b/lisp/progmodes/ruby-mode.el
index 84ac8fdb28..35772827ce 100644
--- a/lisp/progmodes/ruby-mode.el
+++ b/lisp/progmodes/ruby-mode.el
@@ -291,6 +291,7 @@ ruby-deep-indent-paren-style

 (defcustom ruby-encoding-map
   '((us-ascii       . nil)       ;; Do not put coding: us-ascii
+    (utf-8          . nil)       ;; Default since Ruby 2.0
     (shift-jis      . cp932)     ;; Emacs charset name of Shift_JIS
     (shift_jis      . cp932)     ;; MIME charset name of Shift_JIS
     (japanese-cp932 . cp932))    ;; Emacs charset name of CP932
@@ -760,7 +761,7 @@ ruby--insert-coding-comment

 (defun ruby--detect-encoding ()
   (if (eq ruby-insert-encoding-magic-comment 'always-utf8)
-      "utf-8"
+      'utf-8
     (let ((coding-system
            (or save-buffer-coding-system
                buffer-file-coding-system)))
@@ -769,12 +770,11 @@ ruby--detect-encoding
                 (or (coding-system-get coding-system 'mime-charset)
                     (coding-system-change-eol-conversion coding-system 
nil))))
       (if coding-system
-          (symbol-name
-           (if ruby-use-encoding-map
-               (let ((elt (assq coding-system ruby-encoding-map)))
-                 (if elt (cdr elt) coding-system))
-             coding-system))
-        "ascii-8bit"))))
+          (if ruby-use-encoding-map
+              (let ((elt (assq coding-system ruby-encoding-map)))
+                (if elt (cdr elt) coding-system))
+            coding-system)
+        'ascii-8bit))))

 (defun ruby--encoding-comment-required-p ()
   (or (eq ruby-insert-encoding-magic-comment 'always-utf8)
@@ -796,7 +796,7 @@ ruby-mode-set-encoding
                    (unless (string= (match-string 2) coding-system)
                      (goto-char (match-beginning 2))
                      (delete-region (point) (match-end 2))
-                     (insert coding-system)))
+                     (insert (symbol-name coding-system))))
                   ((looking-at "\\s *#.*coding\\s *[:=]"))
                   (t (when ruby-insert-encoding-magic-comment
                        (ruby--insert-coding-comment coding-system))))

Message #13 received at 48043 <at> debbugs.gnu.org (full text, mbox):

From: Peter Oliver <p.d.oliver <at> mavit.org.uk>
To: Dmitry Gutov <dgutov <at> yandex.ru>
Cc: 48043 <at> debbugs.gnu.org
Subject: Re: bug#48043: UTF-8 magic comment is unwelcome with recent Ruby
 versions
Date: Tue, 27 Apr 2021 16:29:17 +0100 (BST)

[Message part 1 (text/plain, inline)]

On Tue, 27 Apr 2021, Dmitry Gutov wrote:

> On 26.04.2021 21:28, Peter Oliver wrote:
>
>>  Two patches are attached to address this:
>>
>>  - The first patch adds a new choice to ruby-insert-encoding-magic-comment,
>>  unless-utf8, which causes the magic comment not to be inserted if the
>>  encoding is UTF-8.
>>
>>  - The second patch, perhaps more controversially, makes this the default.
>
> Both changes make sense to me.
>
> However, I've looked at the existing code and found a prior change which 
> intended for this to be more customizable already, yet had a minor bug.
>
> Please try out the following patch:

That works for me, and I think is more straightforward than my approach.  Thanks.

Attached is an additional patch which adapts the tests added in my patch for your patch.

-- 
Peter Oliver

[0001-Test-ruby-mode-set-encoding-with-a-few-different-enc.patch (text/plain, attachment)]

Message #18 received at 48043-done <at> debbugs.gnu.org (full text, mbox):

From: Dmitry Gutov <dgutov <at> yandex.ru>
To: Peter Oliver <p.d.oliver <at> mavit.org.uk>
Cc: 48043-done <at> debbugs.gnu.org
Subject: Re: bug#48043: UTF-8 magic comment is unwelcome with recent Ruby
 versions
Date: Wed, 28 Apr 2021 05:23:56 +0300

Version: 28.1

On 27.04.2021 18:29, Peter Oliver wrote:

> That works for me, and I think is more straightforward than my 
> approach.  Thanks.
> 
> Attached is an additional patch which adapts the tests added in my patch 
> for your patch.

Thanks! I've pushed the change and the tests to master.

Please note that since (AFAICT) you don't have FSF copyright assignment 
on file this exhausts the allowed limit for code contributions to Emacs.

Would you like us to send you the assignment form, so that the next 
patch could be accepted without reservation?

Message #21 received at 48043-done <at> debbugs.gnu.org (full text, mbox):

From: Peter Oliver <p.d.oliver <at> mavit.org.uk>
To: Dmitry Gutov <dgutov <at> yandex.ru>
Cc: 48043-done <at> debbugs.gnu.org
Subject: Re: bug#48043: UTF-8 magic comment is unwelcome with recent Ruby
 versions
Date: Wed, 28 Apr 2021 12:59:32 +0100 (BST)

On Wed, 28 Apr 2021, Dmitry Gutov wrote:

> Please note that since (AFAICT) you don't have FSF copyright assignment on 
> file this exhausts the allowed limit for code contributions to Emacs.
>
> Would you like us to send you the assignment form, so that the next patch 
> could be accepted without reservation?

Yes please.

-- 
Peter Oliver

Message #24 received at 48043-done <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Peter Oliver <p.d.oliver <at> mavit.org.uk>
Cc: 48043-done <at> debbugs.gnu.org, dgutov <at> yandex.ru
Subject: Re: bug#48043: UTF-8 magic comment is unwelcome with recent Ruby
 versions
Date: Wed, 28 Apr 2021 15:28:57 +0300

> Date: Wed, 28 Apr 2021 12:59:32 +0100 (BST)
> From: Peter Oliver <p.d.oliver <at> mavit.org.uk>
> Cc: 48043-done <at> debbugs.gnu.org
> 
> > Would you like us to send you the assignment form, so that the next patch 
> > could be accepted without reservation?
> 
> Yes please.

Thanks, form sent off-list.

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