bug#5586: 23.1.92.1; Electric indentation and hungry backspace deletion in JavaScript mode (js-mode)

bug#5586: 23.1.92.1; Electric indentation and hungry backspace deletion in JavaScript mode (js-mode)

[Paul Pogonyshev]

Package: emacs
Severity: wishlist

JavaScript is quite similar in syntax to C-like languages (Java, C++
etc.), so it's natural to use the same editing techniques for it.  It
would be nice if Emacs gave JS mode a more "familiar" feel.

For me, the most wanted features are electric indentation and hungry
backspace.  I.e. when typing '{', '(' or a similar control character
the current line would be automatically reindented.  And backspace
would delete all space characters to the left of the point, not just
one.

Paul

bug#5586: 23.1.92.1; Electric indentation and hungry backspace deletion in JavaScript mode (js-mode)

[Daniel Colascione]

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On 2/16/10 5:31 PM, Paul Pogonyshev wrote:
> Package: emacs
> Severity: wishlist
> 
> JavaScript is quite similar in syntax to C-like languages (Java, C++
> etc.), so it's natural to use the same editing techniques for it.  It
> would be nice if Emacs gave JS mode a more "familiar" feel.
> 
> For me, the most wanted features are electric indentation and hungry
> backspace.  I.e. when typing '{', '(' or a similar control character
> the current line would be automatically reindented.  And backspace
> would delete all space characters to the left of the point, not just
> one.
> 
> Paul

espresso-mode actually had electric indentation when I submitted it for
inclusion in Emacs. Can we restore that functionality?
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bug#5586: 23.1.92.1; Electric indentation and hungry backspace deletion in JavaScript mode (js-mode)

[Chong Yidong]

> espresso-mode actually had electric indentation when I submitted it
> for inclusion in Emacs. Can we restore that functionality?

You're right, it was a mistake to take that out, since CC mode also has
electric punctuation.

I am still not happy about the way it's implemented in either mode---I
think Emacs needs some kind of centralized mechanism for this---but that
is a longer-term project.  In the meantime, I've restored the deleted
code in the branch.

One difference, however, is that espresso-mode did electric punctuation
for `+-.'.  I didn't restore this yet, since CC mode does not do
electric punctuation for these characters.  Is there any reason we need
to do this specially for Javascript?

bug#5586: 23.1.92.1; Electric indentation and hungry backspace deletion in JavaScript mode (js-mode)

[Daniel Colascione]

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On 3/28/10 4:46 PM, Chong Yidong wrote:
> I am still not happy about the way it's implemented in either mode---I
> think Emacs needs some kind of centralized mechanism for this---but that
> is a longer-term project.  

The chief difficulty I see is that in some modes, indentation isn't
idempotent: if you ran indent-line-function from some generic electric
code, it might change the indentation of the current line in unwanted
ways. (Imagine python-mode, where indent-line-function cycles through
feasible indentation levels for a given line.)

At best, modes would have to opt-in, and if each mode needs some glue
anyway, why not just let each mode handle electric characters itself?

> In the meantime, I've restored the deleted
> code in the branch.

Thanks.

> One difference, however, is that espresso-mode did electric punctuation
> for `+-.'.  I didn't restore this yet, since CC mode does not do
> electric punctuation for these characters.  Is there any reason we need
> to do this specially for Javascript?

There's no particular reason, no. The cc-mode set of electric characters
is probably fine.

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bug#5586: 23.1.92.1; Electric indentation and hungry backspace deletion in JavaScript mode (js-mode)

[Daniel Colascione]

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On 3/28/10 4:46 PM, Chong Yidong wrote:
> I am still not happy about the way it's implemented in either mode---I
> think Emacs needs some kind of centralized mechanism for this---but that
> is a longer-term project.  

The chief difficulty I see is that in some modes, indentation isn't
idempotent: if you ran indent-line-function from some generic electric
code, it might change the indentation of the current line in unwanted
ways. (Imagine python-mode, where indent-line-function cycles through
feasible indentation levels for a given line.)

At best, modes would have to opt-in, and if each mode needs some glue
anyway, why not just let each mode handle electric characters itself?

> In the meantime, I've restored the deleted
> code in the branch.

Thanks.

> One difference, however, is that espresso-mode did electric punctuation
> for `+-.'.  I didn't restore this yet, since CC mode does not do
> electric punctuation for these characters.  Is there any reason we need
> to do this specially for Javascript?

There's no particular reason, no. The cc-mode set of electric characters
is probably fine.

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bug#5586: 23.1.92.1; Electric indentation and hungry backspace deletion in JavaScript mode (js-mode)

[Lennart Borgman]

On Sun, Mar 28, 2010 at 10:58 PM, Daniel Colascione
<dan.colascione@gmail.com> wrote:
>
> The chief difficulty I see is that in some modes, indentation isn't
> idempotent: if you ran indent-line-function from some generic electric
> code, it might change the indentation of the current line in unwanted
> ways. (Imagine python-mode, where indent-line-function cycles through
> feasible indentation levels for a given line.)
>
> At best, modes would have to opt-in, and if each mode needs some glue
> anyway, why not just let each mode handle electric characters itself?


Because without something like indent-line-function you can not handle
it in a more generic way.

The absense of this in some major modes has for example costed me a
lot of burden in mumamo (the framework in nXhtml for mult major modes
in a buffer). Actually indent-line-function is not generic enough. One
more level is needed: one that computes the desirable indentation.

Electricity (was: bug#5586: 23.1.92.1; Electric indentation and hungry backspace deletion in JavaScript mode (js-mode))

[Stefan Monnier]

> I am still not happy about the way it's implemented in either mode---I
> think Emacs needs some kind of centralized mechanism for this---but that
> is a longer-term project.

Agreed.  If someone could try to survey the different kinds of
"electricity" we have in Emacs packages, and the different ways they can
be configured, it would be a good first step.

Obvious one kind of electricity is when some keys (like ; } and such)
cause reindentation of the current line additionally to self-insert.

Other forms I would consider as potentially connected include:
- SPC in auto-fill-mode
- inserting () when you press just (
- do abbrev expansion when you hit SPC
- newline-and-indent as an electric form of newline
- insert `` or " or '' when you press " in LaTeX


        Stefan

bug#5586: 23.1.92.1; Electric indentation and hungry backspace deletion in JavaScript mode (js-mode)

[Stefan Monnier]

> At best, modes would have to opt-in, and if each mode needs some glue
> anyway, why not just let each mode handle electric characters itself?

For one, it would allow users to turn it on/off globally rather than
having to do it for every mode.  Also every mode shouldn't have to
reinvent it.


        Stefan

bug#5586: is this bug still valid?

[Tom Tromey]

js.el now has:

  (setq-local electric-indent-chars
	      (append "{}():;," electric-indent-chars)) ;FIXME: js2-mode adds "[]*".

... so I think the original request for electric indentation has been
met.

Maybe the FIXME should be addressed by moving "[]" (and "*" - I don't
know that this one is so useful) out of the comment and into the string?

Hungry deletion seems like something that should be done generically in
electric.el.

Tom

bug#5586: 23.1.92.1; Electric indentation and hungry backspace deletion in JavaScript mode (js-mode)

[Lars Ingebrigtsen]

Tom Tromey <tom@tromey.com> writes:

> js.el now has:
>
>   (setq-local electric-indent-chars
> 	      (append "{}():;," electric-indent-chars)) ;FIXME: js2-mode adds "[]*".
>
> ... so I think the original request for electric indentation has been
> met.

I guess so, so I'm closing this bug report.  (If there's more to be done
here, please respond to the debbugs address and we'll reopen.)

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no