Re: whence question

[Ray Andrews <rayandrews@eastlink.ca>]

On 13/01/17 10:48 PM, Daniel Shahaf wrote:
>
> That's only true when 'setopt nonomatch' is in effect, which is not the
> default.  By default, globs that have no match are considered errors.
> The NULL_GLOB option selects a third mode.  See:
>
>      % cd $(mktemp -d)
>      % echo foo*
>      zsh: no matches found: foo*
>      % (setopt nullglob; echo foo*) | nl -ba
>      
>      % (setopt nonomatch; echo foo*)
>      foo*
>      %
I'll take a closer look at those options, I'm always terrified that if I 
play with them I'll set a landmine what will blow up on me latter and 
I'll forget what it is that I changed or why things are broken.   Gotta 
make sure that nullglob and nonomatch don't trip over each other.  But 
first experiments:



> $ unsetopt nullglob; unsetopt nonomatch; whence -ma grub-r*
> $ unsetopt nullglob; setopt nonomatch; whence -ma grub-r*
> $ setopt nullglob; setopt nonomatch; whence -ma grub-r*
> $ setopt nullglob; unsetopt nonomatch; whence -ma grub-r*

Does that contradict? Nuthin' works.
>> [...] I can see that without 'noglob' the shell's zeal for expanding
>> globs is in more or less direct conflict with the intention of the 'm'
>> switch which supposes that whence will handle globing itself.  I can
>> also see that that might not be fixable even in theory for reasons of
>> consistency,

> Also, the existing design has merits: *every* external and builtin
> command parses "words with globbing metacharacters" the same way.
> «echo *foo» and «whence *foo» and «bar *foo» are all subject to the
> same rules.  The rules are consistent for everybody.  That's a feature.
Well, consistency trumps convenience.  Still I'd argue that my original 
example really is a gotcha, it's not something that would ever (?) be 
anticipated.  Just being devil's advocate here of course but in this 
case does not the 'm' switch in effect 'state' an exception?  That is, 
is it not an explicit request to change the rules vis a vis globing?  
Without 'm' I have no expectation that whence has any special power vis 
a vis globing (globbing?) but with 'm' I expect that it does.  Can we 
have intuitive behaviour and consistency if it was a stated principal 
that 'm' (and any other such devices) are immune to the artifact of the 
local match which is in no way a 'natural' target for whence anyway?  
IOW 'whence -ma grub-r*' should never be anything other than a search 
for natural whence targets and the local match could be seen as an 
error. Delicate tho, maybe not.