bug#25670: Feature request: ignore --help in --script mode

bug#25670: Feature request: ignore --help in --script mode

[Clément Pit--Claudel]

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Hi bug-gnu-emacs,

Event with --script, Emacs still displays its help when passed --help.  This is confusing for users (they might write emacs --script some-script.el --help expecting to get help on the script, but instead they get Emacs' help), and it force ELisp scripts to use --usage or some other harder-to-guess synonym.

Could this be changed so that emacs --script a.el --help does not show Emacs' help?

More generally, could we guarantee that options that appear *after* "--script" aren't processed by Emacs itself (and instead left to the script)?  Or would that break things?

Thanks!
Clément.


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bug#25670: Feature request: ignore --help in --script mode

[Glenn Morris]

AFAICS a simple shell-script wrapper removes the need for --script
altogether, so it's hard to get motivated to improve it. Eg

#!/bin/sh

... --help parsing goes here ...

exec emacs -batch -l script.el

bug#25670: Feature request: ignore --help in --script mode

[Ted Zlatanov]

On Thu, 9 Feb 2017 16:00:59 -0500 Clément Pit--Claudel <clement.pitclaudel@live.com> wrote: 

CP> More generally, could we guarantee that options that appear *after* "--script" aren't processed by Emacs itself (and instead left to the script)?  Or would that break things?

Typically I've seen "--" used to indicate the end of parseable options.
Would it help?

If so, I think it makes sense to support that in Emacs. There may be
other future uses of it besides scripting.

Ted

bug#25670: Feature request: ignore --help in --script mode

[Clément Pit--Claudel]

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On 2017-02-10 10:05, Ted Zlatanov wrote:
> On Thu, 9 Feb 2017 16:00:59 -0500 Clément Pit--Claudel <clement.pitclaudel@live.com> wrote: 
> 
> CP> More generally, could we guarantee that options that appear *after* "--script" aren't processed by Emacs itself (and instead left to the script)?  Or would that break things?
> 
> Typically I've seen "--" used to indicate the end of parseable options.
> Would it help?

Yes! And in fact it seems to work :) Neat.

$ emacs -Q --batch --eval '(print argv)' -- --help
("--" "--help")

I see now that it was mentioned in http://www.lunaryorn.com/posts/emacs-script-pitfalls.html.  Not sure how I missed it.

Thanks Ted!
Clément.


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bug#25670: Feature request: ignore --help in --script mode

[Glenn Morris]

Clément Pit--Claudel wrote:

> $ emacs -Q --batch --eval '(print argv)' -- --help
> ("--" "--help")

If you can train your users to insert -- before --help, you could get
them to use any other flag for help. And if you are inserting the -- for
them, you are already using a wrapper.

bug#25670: Feature request: ignore --help in --script mode

[Clément Pit--Claudel]

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On 2017-02-10 12:36, Glenn Morris wrote:
> Clément Pit--Claudel wrote:
> 
>> $ emacs -Q --batch --eval '(print argv)' -- --help
>> ("--" "--help")
> 
> If you can train your users to insert -- before --help, you could get
> them to use any other flag for help. And if you are inserting the -- for
> them, you are already using a wrapper.

I'm using this as my header:

#!/bin/sh
":"; exec emacs -Q --script "$0" -- "$@" # -*- mode: emacs-lisp; lexical-binding: t; -*-

I don't understand the wrapper point: I want to do the argument parsing in ELisp, not in bash.  Did I misunderstand your suggestion?

Clément.



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bug#25670: Feature request: ignore --help in --script mode

[Eli Zaretskii]

> From: Clément Pit--Claudel <clement.pitclaudel@live.com>
> Date: Thu, 9 Feb 2017 16:00:59 -0500
> 
> Event with --script, Emacs still displays its help when passed --help.  This is confusing for users (they might write emacs --script some-script.el --help expecting to get help on the script, but instead they get Emacs' help), and it force ELisp scripts to use --usage or some other harder-to-guess synonym.
> 
> Could this be changed so that emacs --script a.el --help does not show Emacs' help?

What should be done with --help in that case?

(In general, I'd expect such script not to use --help or --version at
all.)

> More generally, could we guarantee that options that appear *after* "--script" aren't processed by Emacs itself (and instead left to the script)?  Or would that break things?

Which other options should be processed when --script is given?  Are
there any requirements for what command-line-args-left should have
when the script is loaded?

IOW, it is not clear to me what are the expectations in this use case.
Please take a look at how the command-line arguments are processed at
startup, in emacs.c and in startup.el, and make a more detailed
proposal.  Then we could see if it's easy to implement without
potentially breaking anything.

bug#25670: Feature request: ignore --help in --script mode

[Clément Pit--Claudel]

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On 2017-02-18 04:59, Eli Zaretskii wrote:
> IOW, it is not clear to me what are the expectations in this use case.
> Please take a look at how the command-line arguments are processed at
> startup, in emacs.c and in startup.el, and make a more detailed
> proposal.  Then we could see if it's easy to implement without
> potentially breaking anything.

Ted's pointer to Emacs' support for "--" solved this problem for me: when I pass "--" before "--help", Emacs doesn't process "--".  So I don't --script to be special-cased any more :)

Clément.


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bug#25670: Feature request: ignore --help in --script mode

[Eli Zaretskii]

> Cc: 25670@debbugs.gnu.org
> From: Clément Pit--Claudel <clement.pitclaudel@live.com>
> Date: Sat, 18 Feb 2017 08:46:07 -0500
> 
> Ted's pointer to Emacs' support for "--" solved this problem for me: when I pass "--" before "--help", Emacs doesn't process "--".  So I don't --script to be special-cased any more :)

OK, thanks.