GNU bug report logs - #15874
24.3.50; exit! not properly font-locked in ruby-mode

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

From: Bozhidar Batsov <bozhidar <at> batsov.com>
To: bug-gnu-emacs <at> gnu.org
Subject: 24.3.50; exit! not properly font-locked in ruby-mode
Date: Tue, 12 Nov 2013 14:38:29 +0200

The built-in Kernel#exit! method is not properly font-locked. exit is font-locked
with the built-in face, but the ! is font-locked with the default face.



In GNU Emacs 24.3.50.1 (x86_64-apple-darwin13.0.0, NS apple-appkit-1265.00)
 of 2013-11-11 on Bozhidars-MacBook-Pro.local
Windowing system distributor `Apple', version 10.3.1265
Configured using:
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 --enable-locallisppath=/usr/local/share/emacs/site-lisp
 --infodir=/usr/local/Cellar/emacs/HEAD/share/info/emacs
 --without-gnutls --with-ns --disable-ns-self-contained'

Important settings:
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Major mode: Conf[Unix]

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Recent messages:

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Load-path shadows:
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Message #8 received at 15874 <at> debbugs.gnu.org (full text, mbox):

From: Dmitry Gutov <dgutov <at> yandex.ru>
To: Bozhidar Batsov <bozhidar <at> batsov.com>
Cc: 15874 <at> debbugs.gnu.org
Subject: Re: bug#15874: 24.3.50; exit! not properly font-locked in ruby-mode
Date: Wed, 04 Dec 2013 20:31:26 +0200

Bozhidar Batsov <bozhidar <at> batsov.com> writes:

> The built-in Kernel#exit! method is not properly font-locked. exit is
> font-locked with the built-in face, but the ! is font-locked with the
> default face.

Any ideas for a regexp that matches (any) non-symbol character?

http://lists.gnu.org/archive/html/emacs-devel/2013-11/msg00684.html

I'm not sure we want to move `!' to the symbol syntax class. Maybe we
even should move `?' back to punctuation.

Message #11 received at 15874 <at> debbugs.gnu.org (full text, mbox):

From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: Dmitry Gutov <dgutov <at> yandex.ru>
Cc: 15874 <at> debbugs.gnu.org, Bozhidar Batsov <bozhidar <at> batsov.com>
Subject: Re: bug#15874: 24.3.50; exit! not properly font-locked in ruby-mode
Date: Wed, 04 Dec 2013 14:20:29 -0500

> I'm not sure we want to move `!' to the symbol syntax class.

How is the Ruby lexing done w.r.t identifiers and ! (and ?) ?


        Stefan

Message #14 received at 15874 <at> debbugs.gnu.org (full text, mbox):

From: Dmitry Gutov <dgutov <at> yandex.ru>
To: Stefan Monnier <monnier <at> iro.umontreal.ca>
Cc: 15874 <at> debbugs.gnu.org, Bozhidar Batsov <bozhidar <at> batsov.com>
Subject: Re: bug#15874: 24.3.50; exit! not properly font-locked in ruby-mode
Date: Thu, 05 Dec 2013 00:33:06 +0200

On 04.12.2013 21:20, Stefan Monnier wrote:
>> I'm not sure we want to move `!' to the symbol syntax class.
>
> How is the Ruby lexing done w.r.t identifiers and ! (and ?) ?

There's no special handling: ? is considered a part of whatever token 
it's adjacent to (even when the token follows it, ex. "?wut"), and ! is 
considered a separate token.

The former is usually harmless, as far as indentation and syntax 
highlighting are concerned (*), but not considering ! a part of 
preceding token makes us mishandle the (rare, to be sure) method names 
like "else!" and "end!".

(*) Counterexample:

irb(main):013:0> def foo?
irb(main):014:1> 42
irb(main):015:1> end
=> nil
irb(main):016:0> begin; foo?end
=> 42

We don't treat "end" in "begin; foo?end" as a keyword, but ideally, we 
should.

Message #17 received at 15874 <at> debbugs.gnu.org (full text, mbox):

From: Dmitry Gutov <dgutov <at> yandex.ru>
To: Stefan Monnier <monnier <at> iro.umontreal.ca>
Cc: 15874 <at> debbugs.gnu.org, Bozhidar Batsov <bozhidar <at> batsov.com>
Subject: Re: bug#15874: 24.3.50; exit! not properly font-locked in ruby-mode
Date: Thu, 05 Dec 2013 01:15:37 +0200

On 04.12.2013 21:20, Stefan Monnier wrote:
>> I'm not sure we want to move `!' to the symbol syntax class.
>
> How is the Ruby lexing done w.r.t identifiers and ! (and ?) ?

To answer your actual question: Ruby considers ! and ? parts of 
identifiers only in method names, and only when the name ends with one 
such a character.

The names of local variables, as well as instance and global ones, can't 
use ? and !. We may want to handle this eventually:

irb(main):001:0> @abc?1:2
=> 2

irb(main):002:0> abc = 1
=> 1
irb(main):003:0> abc?2:3
SyntaxError: (irb):3: syntax error, unexpected ':', expecting $end

Message #20 received at 15874 <at> debbugs.gnu.org (full text, mbox):

From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: Dmitry Gutov <dgutov <at> yandex.ru>
Cc: 15874 <at> debbugs.gnu.org, Bozhidar Batsov <bozhidar <at> batsov.com>
Subject: Re: bug#15874: 24.3.50; exit! not properly font-locked in ruby-mode
Date: Wed, 04 Dec 2013 21:50:19 -0500

> To answer your actual question: Ruby considers ! and ? parts of identifiers
> only in method names, and only when the name ends with one such a character.

Maybe a good way to handle them is via syntax-propertize, then, especially
if we can come up with a good regexp that distinguishes "method name"
from "local variable name"?


        Stefan

Message #23 received at 15874 <at> debbugs.gnu.org (full text, mbox):

From: Dmitry Gutov <dgutov <at> yandex.ru>
To: Stefan Monnier <monnier <at> iro.umontreal.ca>
Cc: 15874 <at> debbugs.gnu.org, Bozhidar Batsov <bozhidar <at> batsov.com>
Subject: Re: bug#15874: 24.3.50; exit! not properly font-locked in ruby-mode
Date: Thu, 05 Dec 2013 05:42:19 +0200

On 05.12.2013 04:50, Stefan Monnier wrote:
> Maybe a good way to handle them is via syntax-propertize,

Huh yes, that's an approach I haven't considered. But it seems more 
performance-intensive than the other options, at least as long as Emacs 
regexps don't support lookbehind.

If we could match "non-symbols", then the font-lock part of the problem 
would be solved, and appending "?" or "!" in the forward-token and 
backward-token functions would take negligible amount of time.

Say, why don't we have a "non-symbol" matcher? I would think that in 
many cases the regexp engine performs unnecessary work when it sees 
"\\_<" or "\\_>" because we often know in advance that the character 
we've already matched, or will have to match next, is a symbol 
constituent. But the engine has to check.

Most uses of `(regexp-opt '("boats" "boats" "boats") 'symbols)' would 
fall under this scenario.

> then, especially
> if we can come up with a good regexp that distinguishes "method name"
> from "local variable name"?

Not really. References to local variables, unlike instance and global 
ones, are indistinguishable from method calls if we judge only by name.

We could backtrack until the beginning of block or method, look for 
assignments, etc, but that's a lot of work for marginal gain: we can 
just assume that each such reference is a method calls, because 
otherwise it would be syntax error.

Message #26 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Kevin Rodgers <kevin.d.rodgers <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Subject: Re: bug#15874: 24.3.50; exit! not properly font-locked in ruby-mode
Date: Wed, 04 Dec 2013 23:34:35 -0700

On 12/4/13 11:31 AM, Dmitry Gutov wrote:
> Bozhidar Batsov<bozhidar <at> batsov.com>  writes:
>
>> The built-in Kernel#exit! method is not properly font-locked. exit is
>> font-locked with the built-in face, but the ! is font-locked with the
>> default face.
>
> Any ideas for a regexp that matches (any) non-symbol character?

`\sCODE'
     matches any character whose syntax is CODE.  Here CODE is a
     character that represents a syntax code: thus, `w' for word
     constituent, `-' for whitespace, `(' for open parenthesis, etc.
     To represent whitespace syntax, use either `-' or a space
     character.  *Note Syntax Class Table::, for a list of syntax codes
     and the characters that stand for them.

`\SCODE'
     matches any character whose syntax is not CODE.

...

 -- Syntax class: symbol constituent
     "Symbol constituents" (designated by `_') are the extra characters
     that are used in variable and command names along with word
     constituents.  For example, the symbol constituents class is used
     in Lisp mode to indicate that certain characters may be part of
     symbol names even though they are not part of English words.
     These characters are `$&*+-_<>'.  In standard C, the only
     non-word-constituent character that is valid in symbols is
     underscore (`_').

> http://lists.gnu.org/archive/html/emacs-devel/2013-11/msg00684.html
>
> I'm not sure we want to move `!' to the symbol syntax class. Maybe we
> even should move `?' back to punctuation.

-- 
Kevin Rodgers
Denver, Colorado, USA

Message #29 received at 15874 <at> debbugs.gnu.org (full text, mbox):

From: Dmitry Gutov <dgutov <at> yandex.ru>
To: Kevin Rodgers <kevin.d.rodgers <at> gmail.com>
Cc: 15874 <at> debbugs.gnu.org
Subject: Re: bug#15874: 24.3.50; exit! not properly font-locked in ruby-mode
Date: Thu, 05 Dec 2013 12:58:20 +0200

Kevin Rodgers <kevin.d.rodgers <at> gmail.com> writes:

>> Any ideas for a regexp that matches (any) non-symbol character?
>
> `\sCODE'
> `\SCODE'

That doesn't really help, unless we want to enumerate all syntax classes
that we can accept.

Non-symbol character is a character that's not of class "symbol", nor of
class "word". "\\S_" matches words.

Message #32 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Kevin Rodgers <kevin.d.rodgers <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Subject: Re: bug#15874: 24.3.50; exit! not properly font-locked in ruby-mode
Date: Thu, 05 Dec 2013 07:50:49 -0700

On 12/5/13 3:58 AM, Dmitry Gutov wrote:
> Kevin Rodgers<kevin.d.rodgers <at> gmail.com>  writes:
>
>>> Any ideas for a regexp that matches (any) non-symbol character?
>>
>> `\sCODE'
>> `\SCODE'
>
> That doesn't really help, unless we want to enumerate all syntax classes
> that we can accept.
>
> Non-symbol character is a character that's not of class "symbol", nor of
> class "word". "\\S_" matches words.

[^[:symbol:][:word:]]

if the [:symbol:] character class actually existed :-)

-- 
Kevin Rodgers
Denver, Colorado, USA

Message #35 received at 15874 <at> debbugs.gnu.org (full text, mbox):

From: Dmitry Gutov <dgutov <at> yandex.ru>
To: Kevin Rodgers <kevin.d.rodgers <at> gmail.com>
Cc: 15874 <at> debbugs.gnu.org
Subject: Re: bug#15874: 24.3.50; exit! not properly font-locked in ruby-mode
Date: Thu, 05 Dec 2013 19:25:04 +0200

Kevin Rodgers <kevin.d.rodgers <at> gmail.com> writes:

> [^[:symbol:][:word:]]
>
> if the [:symbol:] character class actually existed :-)

Yep, I like this non-existent feature, too. :)

Message #38 received at 15874 <at> debbugs.gnu.org (full text, mbox):

From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: Dmitry Gutov <dgutov <at> yandex.ru>
Cc: 15874 <at> debbugs.gnu.org, Bozhidar Batsov <bozhidar <at> batsov.com>
Subject: Re: bug#15874: 24.3.50; exit! not properly font-locked in ruby-mode
Date: Thu, 05 Dec 2013 14:02:53 -0500

>> Maybe a good way to handle them is via syntax-propertize,
> Huh yes, that's an approach I haven't considered.

The advantage is that it would also fix the sexp-movement operations.

> But it seems more performance-intensive than the other options, at
> least as long as Emacs regexps don't support lookbehind.

I don't see why we'd need lookbehind.
We can use a regexp like "\\(?:\\sw\\|\\s_\\)\\([!?]\\)" and then place
the syntax-table property on the ? (or !) character.

> Say, why don't we have a "non-symbol" matcher?

I'd rather do something a bit more generic, then, like a \\S which can
take a set of syntaxes to exclude.  Or maybe extend the [:foo:]
character classes to allow [:sw:], [:s_:], etc... so we could do
[^[:sw:][:s_:]].

> I would think that in many cases the regexp engine performs
> unnecessary work when it sees "\\_<" or "\\_>" because we often know
> in advance that the character we've already matched, or will have to
> match next, is a symbol constituent. But the engine has to check.

It's not that big of a deal, tho.  I doubt this would ever appear as
a noticeable slowdown.  And with [^[:sw:][:s_:]] you'd have the extra
work of having to handle the EOB case, so you'd have
\(\'\|[^[:sw:][:s_:]]). 

>> then, especially if we can come up with a good regexp that
>> distinguishes "method name" from "local variable name"?
> Not really.  References to local variables, unlike instance and global ones,
> are indistinguishable from method calls if we judge only by name.

But you said that ! and ? are only allowed in method names.  So somehow
Ruby's parser/lexer distinguishes the two cases.  Would a reference to
a variable "foo?" simply always be parsed as "a reference to variable
foo?"  which would later trigger an error because there's no such
variable (because there can't be any such variable)?


        Stefan

Message #41 received at 15874 <at> debbugs.gnu.org (full text, mbox):

From: Dmitry Gutov <dgutov <at> yandex.ru>
To: Stefan Monnier <monnier <at> iro.umontreal.ca>
Cc: 15874 <at> debbugs.gnu.org, Bozhidar Batsov <bozhidar <at> batsov.com>
Subject: Re: bug#15874: 24.3.50; exit! not properly font-locked in ruby-mode
Date: Fri, 06 Dec 2013 04:44:49 +0200

Stefan Monnier <monnier <at> iro.umontreal.ca> writes:

> The advantage is that it would also fix the sexp-movement operations.

Two birds with one stone, yes.

> I don't see why we'd need lookbehind.

Not mandatory, just good for performance, AFAICT. Instead of maching all
identifiers that look like methods and then finding out that most of
them don't end with ? or ! anyway, it would be faster to scan the buffer
for ? or !, and then look a bit back and see if the text before such a
character resembles a method name.

> We can use a regexp like "\\(?:\\sw\\|\\s_\\)\\([!?]\\)" and then place
> the syntax-table property on the ? (or !) character.

Yes, something like that.

> I'd rather do something a bit more generic, then, like a \\S which can
> take a set of syntaxes to exclude.  Or maybe extend the [:foo:]
> character classes to allow [:sw:], [:s_:], etc... so we could do
> [^[:sw:][:s_:]].

That looks good, but, like you mentioned later, if we had a dedicated
backslash-sequence, it could also transparently handle the EOB case.  I
guess, the question is, would it see much use. `regexp-opt' seems to be
the primary use case to me.

> It's not that big of a deal, tho.  I doubt this would ever appear as
> a noticeable slowdown.

That may be true. 

> But you said that ! and ? are only allowed in method names.  So somehow
> Ruby's parser/lexer distinguishes the two cases.  Would a reference to
> a variable "foo?" simply always be parsed as "a reference to variable
> foo?"  which would later trigger an error because there's no such
> variable (because there can't be any such variable)?

Eh, I guess whenever it sees ? or ! at the end of the identifier, the
parser goes with the assumption that it is a method call, because
otherwise it would be a syntax error.

IOW, we only have to worry about @instance and $global variables.

irb(main):022:0* def a
irb(main):023:1> 42
irb(main):024:1> end
=> nil
irb(main):025:0> a?1:2
SyntaxError: (irb):25: syntax error, unexpected ':', expecting $end
a?1:2
    ^
	from /home/gutov/.rbenv/versions/1.9.3-p429/bin/irb:12:in `<main>'
irb(main):026:0> a = 5
=> 5
irb(main):027:0> a?3:4
SyntaxError: (irb):27: syntax error, unexpected ':', expecting $end
a?3:4
    ^
	from /home/gutov/.rbenv/versions/1.9.3-p429/bin/irb:12:in `<main>'
irb(main):028:0> $abc?
irb(main):029:0* 2
SyntaxError: (irb):29: syntax error, unexpected $end, expecting ':'
	from /home/gutov/.rbenv/versions/1.9.3-p429/bin/irb:12:in `<main>'
irb(main):030:0> $abc = 6
=> 6
irb(main):031:0> $abc?1:2
=> 1

Message #46 received at 15874-done <at> debbugs.gnu.org (full text, mbox):

From: Dmitry Gutov <dgutov <at> yandex.ru>
To: Stefan Monnier <monnier <at> iro.umontreal.ca>
Cc: 15874-done <at> debbugs.gnu.org, Bozhidar Batsov <bozhidar <at> batsov.com>
Subject: Re: bug#15874: 24.3.50; exit! not properly font-locked in ruby-mode
Date: Fri, 06 Dec 2013 06:23:34 +0200

Version: 24.4

Well, it was easier than expected. Stefan, thanks for the advice.

Message #49 received at 15874 <at> debbugs.gnu.org (full text, mbox):

From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: Dmitry Gutov <dgutov <at> yandex.ru>
Cc: 15874 <at> debbugs.gnu.org, Bozhidar Batsov <bozhidar <at> batsov.com>
Subject: Re: bug#15874: 24.3.50; exit! not properly font-locked in ruby-mode
Date: Thu, 05 Dec 2013 23:57:49 -0500

> Not mandatory, just good for performance, AFAICT. Instead of maching all
> identifiers that look like methods and then finding out that most of
> them don't end with ? or ! anyway, it would be faster to scan the buffer
> for ? or !, and then look a bit back and see if the text before such a
> character resembles a method name.

We can also do that, using a "[?!]" regexp and then do the "look a bit
back" in Elisp.

> That looks good, but, like you mentioned later, if we had a dedicated
> backslash-sequence, it could also transparently handle the EOB case.
> I guess, the question is, would it see much use.

But then it would be a lot more special cased.

> `regexp-opt' seems to be the primary use case to me.

I think the second arg to `regexp-opt' is a misfeature.

> irb(main):026:0> a = 5
> => 5
> irb(main):027:0> a?3:4
> SyntaxError: (irb):27: syntax error, unexpected ':', expecting $end
> a?3:4
>     ^
> 	from /home/gutov/.rbenv/versions/1.9.3-p429/bin/irb:12:in `<main>'

Good.


        Stefan

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