bad comment indentation in Emacs Lisp

bad comment indentation in Emacs Lisp

[Drew Adams]

Put this in Emacs Lisp mode and use `C-M-q' at the beginning:
 
(let (;; foobar
      ;; toto
      (titi...)))
 
You get this:
 
(let ( ;; foobar
      ;; toto
      (titi...)))
 
However, if you just use TAB on each line, you don't get that.
 
To me, this is a bug.  `;;' comments should be aligned just as
TAB would align them, always.  `C-M-q' should be equivalent to
using both TAB and `M-;' on each line of the sexp.

Also, in a situation like the preceding, it is likely that you
want the two comments to line up.

In GNU Emacs 22.1.90.1 (i386-mingw-nt5.1.2600)
 of 2008-01-30 on PRETEST
Windowing system distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc (3.4) --cflags -Ic:/gnuwin32/include'
 

Re: bad comment indentation in Emacs Lisp

[Richard Stallman]

The principle he cites is correct -- could you please fix this
and ack?

From: "Drew Adams" <drew.adams@oracle.com>
To: <emacs-pretest-bug@gnu.org>
Date: Tue, 5 Feb 2008 15:10:03 -0800
Message-ID: <009c01c8684c$3dcb3570$0059908d@us.oracle.com>
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Subject: bad comment indentation in Emacs Lisp

Put this in Emacs Lisp mode and use `C-M-q' at the beginning:
 
(let (;; foobar
      ;; toto
      (titi...)))
 
You get this:
 
(let ( ;; foobar
      ;; toto
      (titi...)))
 
However, if you just use TAB on each line, you don't get that.
 
To me, this is a bug.  `;;' comments should be aligned just as
TAB would align them, always.  `C-M-q' should be equivalent to
using both TAB and `M-;' on each line of the sexp.

Also, in a situation like the preceding, it is likely that you
want the two comments to line up.

In GNU Emacs 22.1.90.1 (i386-mingw-nt5.1.2600)
 of 2008-01-30 on PRETEST
Windowing system distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc (3.4) --cflags -Ic:/gnuwin32/include'
 

Re: bad comment indentation in Emacs Lisp

[Stefan Monnier]

> The principle he cites is correct -- could you please fix this
> and ack?

I don't see in what way the behavior doesn't follow the principle proposed.

> Put this in Emacs Lisp mode and use `C-M-q' at the beginning:
 
> (let (;; foobar
>       ;; toto
>       (titi...)))
 
> You get this:
 
> (let ( ;; foobar
>       ;; toto
>       (titi...)))
 
> However, if you just use TAB on each line, you don't get that.

Right, because indent-region does both TAB and M-; on each line (more
or less).
 
> To me, this is a bug.  `;;' comments should be aligned just as
> TAB would align them, always.

TAB generally doesn't touch the comments unless the line itself starts
with a comment.

> `C-M-q' should be equivalent to using both TAB and `M-;' on each line
> of the sexp.

That's indeed what it does.

> Also, in a situation like the preceding, it is likely that you
> want the two comments to line up.

It's possible, but not sure.  Use a single ";" to get comments aligned.
And use ";;" but put each comment-line on its own line.  This way,
there won't be any ambiguity and they'll be aligned.


        Stefan

RE: bad comment indentation in Emacs Lisp

[Drew Adams]

> > The principle he cites is correct -- could you please fix this
> > and ack?
> 
> I don't see in what way the behavior doesn't follow the 
> principle proposed.
> 
> > Put this in Emacs Lisp mode and use `C-M-q' at the beginning:
> > (let (;; foobar
> >       ;; toto
> >       (titi...)))
> > 
> > You get this:
> > (let ( ;; foobar
> >       ;; toto
> >       (titi...)))
> >
> > However, if you just use TAB on each line, you don't get that.
> 
> Right, because indent-region does both TAB and M-; on each line (more
> or less).

No. Neither `M-;' nor TAB moves `;;' comments, except that TAB can move a
line that *starts* with `;;'. That is not the case for the `;;' comment that
is moved here.

> > To me, this is a bug.  `;;' comments should be aligned just as
> > TAB would align them, always.
> 
> TAB generally doesn't touch the comments unless the line itself starts
> with a comment.

Precisely. But `C-M-q' *does* now move a comment that does not start a line.
TAB still (thankfully) does not (relative to the rest of its line). `C-M-q'
should not do what neither TAB nor `M-;' does.

> > `C-M-q' should be equivalent to using both TAB and `M-;' on 
> > each line of the sexp.
> 
> That's indeed what it does.

Not at all. See above. Neither TAB nor `M-;' moves the first comment of the
example.

Go line by line, and do both TAB and `M-;' on each line, and you will see
that the first comment does not move. But `C-M-q' now moves it. This is a
regression: As you have agreed, `C-M-q' should do only what TAB plus `M-;'
does.

> > Also, in a situation like the preceding, it is likely that you
> > want the two comments to line up.
> 
> It's possible, but not sure.  Use a single ";" to get 
> comments aligned.

Why? Why should someone need to replace `;;' by `;'? Why should code that
has always used `;;' to resist in-line movement now be indented differently?


Users have always used `;;' that is not at the start of a line to make a
comment stay put - unlike what `;' does wrt `M-;'. That's precisely why
`M-;' was designed not to move `;;'. Inline `;;' has always let you align
(position) comments manually.

`C-M-q', like TAB, should leave `;;' comments alone, unless they start a
line.

> And use ";;" but put each comment-line on its own line.

Why? Why should someone now need to move `;;' comments to their own line,
just so `C-M-q' won't move them?

And note that this new behavior does not even indent the same as either (1)
`;' or (2) `;;' on a line by itself. This is some entirely new indentation:
(presumably) add a space before `;;'.

> This way, there won't be any ambiguity and they'll be aligned.

What ambiguity? There is no ambiguity. The `C-M-q' code has simply been
broken. It has previously always been equivalent to TAB + `M-;' on each
line. What problem is the new behavior intended to solve?

Re: bad comment indentation in Emacs Lisp

[Stefan Monnier]

>> > (let (;; foobar
>> >       ;; toto
>> >       (titi...)))
>> > 
>> > You get this:
>> > (let ( ;; foobar
>> >       ;; toto
>> >       (titi...)))
>> >
>> > However, if you just use TAB on each line, you don't get that.
>> 
>> Right, because indent-region does both TAB and M-; on each line (more
>> or less).

> No. Neither `M-;' nor TAB moves `;;' comments, except that TAB can move a
> line that *starts* with `;;'. That is not the case for the `;;' comment that
> is moved here.

Huh?  Where do you get this idea?  Have you tried M-; on the `let' line?


        Stefan

RE: bad comment indentation in Emacs Lisp

[Drew Adams]

> >> > (let (;; foobar
> >> >       ;; toto
> >> >       (titi...)))
> >> > 
> >> > You get this:
> >> > (let ( ;; foobar
> >> >       ;; toto
> >> >       (titi...)))
> >> >
> >> > However, if you just use TAB on each line, you don't get that.
> >> 
> >> Right, because indent-region does both TAB and M-; on each 
> >> line (more or less).
> 
> > No. Neither `M-;' nor TAB moves `;;' comments, except that 
> > TAB can move a line that *starts* with `;;'. That is not the
> > case for the `;;' comment that is moved here.
> 
> Huh?  Where do you get this idea?  Have you tried M-; on the 
> `let' line?

Hm. I stand corrected.

In Emacs 20 it behaves as I described (both for `M-;' and `C-M-q'). I
thought this was broken in Emacs 22, but it seems it was broken in Emacs 21.
;-) 

I never used Emacs 21 (a giant regression compared with Emacs 20, at least
on Windows), and I didn't bother to test it for this - mea culpa.

What is the rationale for this kind of comment indentation? It certainly
doesn't indent the same as `;' or the same as `;;' at the beginning of a
line. Why insert a single space here - what's the rationale? Why move `;;'
ever, relative to the rest of its line?

Anyway, guess it's too late to complain now...

So please consider this a feature request. Please DTRT by not inserting a
space - never move `;;' (except for line indentation, when it starts a
line).

Re: bad comment indentation in Emacs Lisp

[Stefan Monnier]

> What is the rationale for this kind of comment indentation? It certainly
> doesn't indent the same as `;' or the same as `;;' at the beginning of a
> line. Why insert a single space here - what's the rationale? Why move `;;'
> ever, relative to the rest of its line?

The space is there for aesthetic reasons as well as to make sure the
code and the comment are separate (makes a difference if the code ends
in \ for instance).

Why move it?  Why not?


        Stefan

RE: bad comment indentation in Emacs Lisp

[Drew Adams]

> > What is the rationale for this kind of comment indentation? 
> > It certainly doesn't indent the same as `;' or the same as
> > `;;' at the beginning of a line. Why insert a single space
> > here - what's the rationale? Why move `;;'
> > ever, relative to the rest of its line?
> 
> The space is there for aesthetic reasons

Bof !

> as well as to make sure the code and the comment are separate
> (makes a difference if the code ends in \ for instance).

That would mean bugged code, that's all. Same as if you forget a space in
lots of other contexts. Same as if you type `?' or `"' or `x' instead of
`;'.

> Why move it?  Why not?

Not moving it means programmers can put `;;' comments where they want them
(e.g. aligning) and have them stay put.

Re: bad comment indentation in Emacs Lisp

[Miles Bader]

Stefan Monnier <monnier@iro.umontreal.ca> writes:
>> What is the rationale for this kind of comment indentation? It certainly
>> doesn't indent the same as `;' or the same as `;;' at the beginning of a
>> line. Why insert a single space here - what's the rationale? Why move `;;'
>> ever, relative to the rest of its line?
>
> The space is there for aesthetic reasons as well as to make sure the
> code and the comment are separate (makes a difference if the code ends
> in \ for instance).

I guess the proper place of ";;" when not at line-start is somewhat
ill-defined, but I generally agree with Drew -- the space is ugly, and
feels like an unwanted intrusion by the indenter.

-Miles

-- 
Quack, n. A murderer without a license.

Re: bad comment indentation in Emacs Lisp

[Richard Stallman]

    > (let ( ;; foobar
    >       ;; toto
    >       (titi...)))

    > However, if you just use TAB on each line, you don't get that.

    Right, because indent-region does both TAB and M-; on each line (more
    or less).

You're right.  Sorry.