Re: [Monotone-devel] "throw usage(); " or "N(); " for argument checking?
On Sun, 2009-01-04 at 11:14 -0800, Zack Weinberg wrote:
> >> > A command that does "throw usage()" gives the same result as calling
> >> > "mtn help ", printing full usage info to stderr, where N()
> >> > results in "mtn: misuse: " on stderr and will put a note in any
> >> > debug log.
> >>
> >> As long as the is maintained in case of "throw usage()", I'm
> >> fine. I dislike tools which just throw the complete usage page at me and
> >> let me figure myself. Some hint on what's wrong certainly helps. And
> >> that hint should survive, IMO.
> >
> > So I guess we should standardize on "throw usage()", but give usage a
> > what() and make the constructor take a message.
>
> I'm dubious about printing the full usage message on any command line
> mistake. Those are often long enough that they make the actual
> diagnostic scroll off the top of the terminal or at least be visually
> lost in a sea of chatter.
Hmm, plus there's the question of where to draw the line. Wrong number
of arguments (easy)? Missing required --options? Options that are only
required because of the number of arguments (like with 'mtn revert')?
Nonsensical combinations of options (--message with --message-file)?
Invalid argument types ('mtn approve not_a_revision_id')? Any
distinction would be somewhat arbitrary, and therefore
annoying/confusing...
> What would be really good is if we could give customized usage advice
> based on the error, e.g. currently we have
>
> $ mtn ls
> mtn: misuse: no subcommand specified for 'ls'
>
> but 'mtn help ls' prints a 55-line message the relevant part of which
> is in the *middle.* It would be great if we could extract just the
> "subcommands of 'mtn ls'" part of that message and print it after the
> above diagnostic.
>
> zw
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Re: [Monotone-devel] "throw usage(); " or "N(); " for argument checking?
Zack Weinberg schrieb: A command that does "throw usage()" gives the same result as calling "mtn help ", printing full usage info to stderr, where N() results in "mtn: misuse: " on stderr and will put a note in any debug log. >>> As long as the is maintained in case of "throw usage()", I'm >>> fine. I dislike tools which just throw the complete usage page at me and >>> let me figure myself. Some hint on what's wrong certainly helps. And >>> that hint should survive, IMO. >> So I guess we should standardize on "throw usage()", but give usage a >> what() and make the constructor take a message. > > I'm dubious about printing the full usage message on any command line > mistake. Those are often long enough that they make the actual > diagnostic scroll off the top of the terminal or at least be visually > lost in a sea of chatter. > > What would be really good is if we could give customized usage advice > based on the error, e.g. currently we have > > $ mtn ls > mtn: misuse: no subcommand specified for 'ls' > > but 'mtn help ls' prints a 55-line message the relevant part of which > is in the *middle.* It would be great if we could extract just the > "subcommands of 'mtn ls'" part of that message and print it after the > above diagnostic. And while we're at it I'd like to add some --show-global-options option to `mtn help' to prevent the additional 22 line output of global options which should be commonly known to users. Or have some `mtn help options' command which does exactly that. Thomas -- GPG-Key 0x160D1092 | tommyd3...@jabber.ccc.de | http://thomaskeller.biz Please note that according to the EU law on data retention, information on every electronic information exchange might be retained for a period of six months or longer: http://www.vorratsdatenspeicherung.de/?lang=en signature.asc Description: OpenPGP digital signature ___ Monotone-devel mailing list Monotone-devel@nongnu.org http://lists.nongnu.org/mailman/listinfo/monotone-devel
Re: [Monotone-devel] "throw usage(); " or "N(); " for argument checking?
On Sun, Jan 4, 2009 at 10:30 AM, Timothy Brownawell wrote: > On Sun, 2009-01-04 at 18:41 +0100, Markus Wanner wrote: >> Timothy Brownawell wrote: >> > "N(false, message)" results in "throw informative_faulure(message)", the >> > question is what to throw rather than whether to throw. >> >> I'm with Timothy on that. These states are exceptional enough and much >> simpler to code. While "control loops" (why a loop, simple conditions >> would do, no?) clutter .. ehm.. exception handling a lot. Yes, especially in the present state where command-line errors are detected within the CMD() function, which is several levels down from the code that generates the usage message. It really is an exceptional transfer of control. >> > A command that does "throw usage()" gives the same result as calling >> > "mtn help ", printing full usage info to stderr, where N() >> > results in "mtn: misuse: " on stderr and will put a note in any >> > debug log. >> >> As long as the is maintained in case of "throw usage()", I'm >> fine. I dislike tools which just throw the complete usage page at me and >> let me figure myself. Some hint on what's wrong certainly helps. And >> that hint should survive, IMO. > > So I guess we should standardize on "throw usage()", but give usage a > what() and make the constructor take a message. I'm dubious about printing the full usage message on any command line mistake. Those are often long enough that they make the actual diagnostic scroll off the top of the terminal or at least be visually lost in a sea of chatter. What would be really good is if we could give customized usage advice based on the error, e.g. currently we have $ mtn ls mtn: misuse: no subcommand specified for 'ls' but 'mtn help ls' prints a 55-line message the relevant part of which is in the *middle.* It would be great if we could extract just the "subcommands of 'mtn ls'" part of that message and print it after the above diagnostic. zw ___ Monotone-devel mailing list Monotone-devel@nongnu.org http://lists.nongnu.org/mailman/listinfo/monotone-devel
Re: [Monotone-devel] "throw usage(); " or "N(); " for argument checking?
On Sun, 2009-01-04 at 18:41 +0100, Markus Wanner wrote: > Hi, > > Timothy Brownawell wrote: > > "N(false, message)" results in "throw informative_faulure(message)", the > > question is what to throw rather than whether to throw. > > I'm with Timothy on that. These states are exceptional enough and much > simpler to code. While "control loops" (why a loop, simple conditions > would do, no?) clutter .. ehm.. exception handling a lot. > > > A command that does "throw usage()" gives the same result as calling > > "mtn help ", printing full usage info to stderr, where N() > > results in "mtn: misuse: " on stderr and will put a note in any > > debug log. > > As long as the is maintained in case of "throw usage()", I'm > fine. I dislike tools which just throw the complete usage page at me and > let me figure myself. Some hint on what's wrong certainly helps. And > that hint should survive, IMO. So I guess we should standardize on "throw usage()", but give usage a what() and make the constructor take a message. -- Timothy Free (experimental) public monotone hosting: http://mtn-host.prjek.net ___ Monotone-devel mailing list Monotone-devel@nongnu.org http://lists.nongnu.org/mailman/listinfo/monotone-devel
Re: [Monotone-devel] "throw usage(); " or "N(); " for argument checking?
Hi, LeJacq, Jean Pierre wrote: > Two considerations: > > 1. N() can always be modified to provide an alternate implementation, >though I acknowledge that changing from throw semantics >would be problematic. For example, adding logging before the throw. Isn't this exactly what Timothy proposes? Clearer separation of the two. > 2. N() is not the best choice for handling this to begin with. Agreed. Timothy proposed using "throw usage();" instead, which is according to these two requests, AFAICT. Regards Markus Wanner ___ Monotone-devel mailing list Monotone-devel@nongnu.org http://lists.nongnu.org/mailman/listinfo/monotone-devel
Re: [Monotone-devel] "throw usage(); " or "N(); " for argument checking?
On Sunday 2009 January 04 11:41:46 Timothy Brownawell wrote:
> On Sun, 2009-01-04 at 11:24 -0500, LeJacq, Jean Pierre wrote:
> > On Saturday 2009 January 03 20:56:52 Timothy Brownawell wrote:
> > > Many commands check for eg the right number of arguments like so:
> > >
> > > if (args.size() != 3)
> > > throw usage(execid);
> > >
> > > where others do
> > >
> > > N(args.size() == 0,
> > > F("no arguments needed"));
> > >
> > >
> > > This ought to be made consistent, does anyone object to using the
> > > 'throw usage();' version everywhere?
> >
> > I recommend the inverse. Exceptions should be reserved for, well
> > "exceptional" situations. Validation of inputs doesn't fall into
> > this category and is more properly handled by normal control loops.
>
> "N(false, message)" results in "throw informative_faulure(message)", the
> question is what to throw rather than whether to throw.
Two considerations:
1. N() can always be modified to provide an alternate implementation,
though I acknowledge that changing from throw semantics
would be problematic. For example, adding logging before the throw.
2. N() is not the best choice for handling this to begin with.
--
JP
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Re: [Monotone-devel] "throw usage(); " or "N(); " for argument checking?
Hi, Timothy Brownawell wrote: > "N(false, message)" results in "throw informative_faulure(message)", the > question is what to throw rather than whether to throw. I'm with Timothy on that. These states are exceptional enough and much simpler to code. While "control loops" (why a loop, simple conditions would do, no?) clutter .. ehm.. exception handling a lot. > A command that does "throw usage()" gives the same result as calling > "mtn help ", printing full usage info to stderr, where N() > results in "mtn: misuse: " on stderr and will put a note in any > debug log. As long as the is maintained in case of "throw usage()", I'm fine. I dislike tools which just throw the complete usage page at me and let me figure myself. Some hint on what's wrong certainly helps. And that hint should survive, IMO. Regards Markus Wanner ___ Monotone-devel mailing list Monotone-devel@nongnu.org http://lists.nongnu.org/mailman/listinfo/monotone-devel
Re: [Monotone-devel] "throw usage(); " or "N(); " for argument checking?
On Sun, 2009-01-04 at 11:24 -0500, LeJacq, Jean Pierre wrote:
> On Saturday 2009 January 03 20:56:52 Timothy Brownawell wrote:
> > Many commands check for eg the right number of arguments like so:
> >
> > if (args.size() != 3)
> > throw usage(execid);
> >
> > where others do
> >
> > N(args.size() == 0,
> > F("no arguments needed"));
> >
> >
> > This ought to be made consistent, does anyone object to using the
> > 'throw usage();' version everywhere?
>
> I recommend the inverse. Exceptions should be reserved for, well
> "exceptional" situations. Validation of inputs doesn't fall into
> this category and is more properly handled by normal control loops.
"N(false, message)" results in "throw informative_faulure(message)", the
question is what to throw rather than whether to throw.
A command that does "throw usage()" gives the same result as calling
"mtn help ", printing full usage info to stderr, where N()
results in "mtn: misuse: " on stderr and will put a note in any
debug log.
--
Timothy
Free (experimental) public monotone hosting: http://mtn-host.prjek.net
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Re: [Monotone-devel] "throw usage(); " or "N(); " for argument checking?
On Saturday 2009 January 03 20:56:52 Timothy Brownawell wrote:
> Many commands check for eg the right number of arguments like so:
>
> if (args.size() != 3)
> throw usage(execid);
>
> where others do
>
> N(args.size() == 0,
> F("no arguments needed"));
>
>
> This ought to be made consistent, does anyone object to using the
> 'throw usage();' version everywhere?
I recommend the inverse. Exceptions should be reserved for, well
"exceptional" situations. Validation of inputs doesn't fall into
this category and is more properly handled by normal control loops.
--
JP
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Re: [Monotone-devel] "throw usage(); " or "N(); " for argument checking?
Timothy Brownawell schrieb:
> Many commands check for eg the right number of arguments like so:
>
> if (args.size() != 3)
> throw usage(execid);
>
> where others do
>
> N(args.size() == 0,
> F("no arguments needed"));
>
>
> This ought to be made consistent, does anyone object to using the
> 'throw usage();' version everywhere?
The only thing which comes into my mind is the automation interface here
- we don't want to provide the full-blown (localized) help output to the
interface here, but rather a hint that the call wasn't syntactically
correct.
This reminds me on something I have on my wishlist - while syntactic
option errors (ie. an option does not exist or is invalid for a given
command) are handled before a command is executed, the argument checking
happens in the command itself. This is usually not a problem, unless we
really want to distinguish between syntax errors and other runtime
errors f.e. in automate...
Thomas.
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[Monotone-devel] "throw usage();" or "N();" for argument checking?
Many commands check for eg the right number of arguments like so:
if (args.size() != 3)
throw usage(execid);
where others do
N(args.size() == 0,
F("no arguments needed"));
This ought to be made consistent, does anyone object to using the
'throw usage();' version everywhere?
--
Timothy
Free (experimental) public monotone hosting: http://mtn-host.prjek.net
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