bug#18379: 24.3.93; Bash font lock: pretty inconsistent treatment of `` and $()

bug#18379: 24.3.93; Bash font lock: pretty inconsistent treatment of `` and $()

[Carlos Pita]

The syntax table treats ` as an string quote character, so

`if [[ $x == x ]]; then echo x; else echo y fi`

$(if [[ $x == x ]]; then echo x; else echo y fi)

are highlighted in a very different way although they are semantically
equivalent.

Related to do above, I don't know whether the different highlighting of
the first word in:

$(if [[ $x == x ]]; then echo x; else echo y fi)

if [[ $x == x ]]; then echo x; else echo y fi

is intended or accidental, but it looks pretty weird. Moreover

$([[ $x == x ]] && echo x)

[[ $x == x ]] && echo x

will highlight exactly equal, which is not consistent with the previous
example.

All in all, I would suggest to:

1) Highlight $(...) and `...` the same way.

2) Don't set the face of the first symbol following $( in any special
way.

Regards
--
Carlos



In GNU Emacs 24.3.93.1 (x86_64-unknown-linux-gnu, GTK+ Version 3.12.2)
 of 2014-08-27 on carlos
Windowing system distributor `The X.Org Foundation', version 11.0.11600000
Configured using:
 `configure --prefix=/usr --sysconfdir=/etc --libexecdir=/usr/lib
 --localstatedir=/var --with-x-toolkit=gtk3 --with-xft
 'CFLAGS=-march=x86-64 -mtune=generic -O2 -pipe -fstack-protector-strong
 --param=ssp-buffer-size=4' CPPFLAGS=-D_FORTIFY_SOURCE=2
 LDFLAGS=-Wl,-O1,--sort-common,--as-needed,-z,relro'

Important settings:
  value of $LC_COLLATE: en_US.UTF-8
  value of $LC_CTYPE: en_US.UTF-8
  value of $LC_MESSAGES: en_US.UTF-8
  value of $LC_MONETARY: en_US.UTF-8
  value of $LC_NUMERIC: en_US.UTF-8
  value of $LC_TIME: en_US.UTF-8
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Shell-script

Minor modes in effect:
  shell-dirtrack-mode: t
  sh-electric-here-document-mode: t
  show-paren-mode: t
  eldoc-mode: t
  yas-global-mode: t
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  ido-ubiquitous-mode: t
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  auto-encryption-mode: t
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Recent input:
( ( x ) ) SPC & & S-SPC l s SPC " x " ) <return> $ 
( l s <backspace> <backspace> [ [ SPC $ x SPC ] ] SPC 
& & SPC l s SPC " x " ) <return> $ ( <backspace> <backspace> 
<up> C-k C-y <return> <return> C-y C-a " C-e " <up> 
<up> <down> <down> C-a C-SPC <down> M-w <down> C-y 
<up> <right> <right> <right> C-d C-d C-d C-d ( ( <right> 
<right> <right> <right> <backspace> <backspace> <backspace> 
) ) <up> <up> C-x C-s <down> <down> <down> <up> e <return> 
<backspace> <backspace> C-e <return> <up> <up> <up> 
<up> <up> <up> <up> C-SPC <down> <down> <down> <down> 
M-w <down> <return> <return> <up> <up> C-y <up> <up> 
<up> <up> C-v <down> <down> <down> <right> <up> <up> 
<up> <left> <left> C-SPC C-g <down> C-SPC <down> <down> 
<down> <right> <left> C-x r t " <return> <right> <right> 
<right> <right> <right> <right> <right> <right> <right> 
<right> <right> <right> <right> <right> <right> <right> 
<up> <up> <up> " <down> C-e " <down> C-e " <down> C-e 
" <down> <return> <return> <up> <up> <up> <up> <up> 
<up> <up> <up> C-SPC <down> M-w <down> <down> <down> 
<down> <down> <down> C-y <up> C-e <left> <left> <left> 
<left> <left> <backspace> <backspace> i f <right> <right> 
<right> <right> SPC f i <down> <up> <return> C-/ <left> 
<left> <right> <right> <backspace> <backspace> f i 
C-g <up> <down> <left> <left> <left> <right> <backspace> 
<return> <up> <down> M-^ <up> C-x C-s <down> <right> 
<right> <right> <right> <right> <right> <right> <right> 
<right> <right> <right> <right> <right> <right> <right> 
<right> <right> <right> <right> <right> ; <down> C-x 
C-s <down> <down> <up> <up> <up> C-SPC <down> M-w <down> 
<up> C-y C-a <up> C-d C-d ` C-e <backspace> ` <down> 
<down> M-x r e p o <tab> r t - e <tab> <return>

Recent messages:
[yas] Snippet 0 exited.
Undo!
Quit
Saving file /tmp/test.sh...
Wrote /tmp/test.sh
Saving file /tmp/test.sh...
Wrote /tmp/test.sh
Mark activated
Mark set
Making completion list...

Load-path shadows:
~/.emacs.d/lisp/rmail hides /usr/share/emacs/24.3.93/lisp/mail/rmail

Features:
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Memory information:
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 (symbols 48 57188 0)
 (miscs 40 3530 2211)
 (strings 32 220578 14464)
 (string-bytes 1 4703140)
 (vectors 16 51134)
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bug#18379: 24.3.93; Bash font lock: pretty inconsistent treatment of `` and $()

[Andreas Schwab]

Carlos Pita <carlosjosepita@gmail.com> writes:

> The syntax table treats ` as an string quote character, so
>
> `if [[ $x == x ]]; then echo x; else echo y fi`
>
> $(if [[ $x == x ]]; then echo x; else echo y fi)
>
> are highlighted in a very different way although they are semantically
> equivalent.

They have different quoting rules, with `...` using rules similar to
double quotes, whereas $(...) is a fully nesting construct.

Andreas.

-- 
Andreas Schwab, SUSE Labs, schwab@suse.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE  1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."

bug#18379: 24.3.93; Bash font lock: pretty inconsistent treatment of `` and $()

[Carlos Pita]

Hi Andreas,

> They have different quoting rules, with `...` using rules similar to
> double quotes, whereas $(...) is a fully nesting construct.

True, but both contains bash code for a subshell which is far from being
an uninterpreted string. IMO the important distintion to highlight is
"intepreted code" vs "uninterpreted string", not the ability to nest vs
the inability to nest (due to different quoting rules).

I've been checking how other editors do this. vim works the way I'm
proposing, while scintilla based editors do it the emacs way. Regarding
my second observation before, neither vim nor scintilla treat the
leading word in a command substution in any special way, which I think
is sensible.

Cheers
--
Carlos

bug#18379: 24.3.93; Bash font lock: pretty inconsistent treatment of `` and $()

[Stefan Monnier]

> The syntax table treats ` as an string quote character, so
>
> `if [[ $x == x ]]; then echo x; else echo y fi`
> $(if [[ $x == x ]]; then echo x; else echo y fi)
>
> are highlighted in a very different way although they are semantically
> equivalent.

This is largely historical, I think (with the $(...) highlighting
appearing more recently).  I don't have a strong opinion either way, but
highlighting it differently could be construed as a feature as well
(letting the user choose between the two quoting mechanisms based on
how she likes it to be highlighted).

IOW we could change it, but the motivation to do so is not very high and
it's not "obviously better".

> Related to do above, I don't know whether the different highlighting of
> the first word in:
>
> $(if [[ $x == x ]]; then echo x; else echo y fi)
> if [[ $x == x ]]; then echo x; else echo y fi
>
> is intended or accidental, but it looks pretty weird.

I don't know either, but I agree it's weird.  Patch welcome.


        Stefan