Re: realpath(3), symlinks, '..' components, and the ':A' word modifier

[Filipe <filipe.silva@xxxxxxxxx>]

having a script broken by upgrading is such a painful, awful experience.

Couldn't we create another modifier that behaves like realpath? e.g. (:Ar) or even add an option to trigger this realpath compatible behaviour? 

> On 5 de jul de 2016, at 10:24, Vadim Zeitlin <vz-zsh@xxxxxxxxxxxx> wrote:
> 
> On Tue, 05 Jul 2016 04:57:56 +0000 Daniel Shahaf <d.s@xxxxxxxxxxxxxxxxxx> wrote:
> 
> DS> Feedback is sought for a proposed behaviour change to the shell.
> DS> 
> DS> Currently, the ':a' word modifier removes '..' component from a path —
> DS> using a purely syntactic transformation, i.e., without consulting the
> DS> filesystem at all — and ':A' does the same and then resolves symlinks
> DS> [so no path component in the result is a symlink].
> DS> 
> DS> It has been proposed to change the semantics of :A to resolve symlinks
> DS> first and '..' components second, like the realpath(3) library function
> DS> does.
> DS> 
> DS> Under the incumbent semantics, $foo:A denotes the same file as $foo:a
> DS> (but not necessarily the same file as $foo).  Under the proposed
> DS> semantics, $foo:A denotes the same file as $foo (but not necesarily the
> DS> same file as $foo:a).
> DS> 
> DS> Would this change be a good idea?
> 
> Hello,
> 
> I am not sure why would this be a good idea, the only argument for it I
> see is compatibility with realpath(), but how much does it really matter?
> There would seem to be quite a few flags/modifiers not corresponding to any
> C library functions, so this doesn't seem like such an egregious exception.
> 
> But this change would be backwards incompatible, if only marginally, and
> my personal test for making breaking changes is whether I could see myself
> justifying them reasonably well to someone whose script has got broken
> after updating the shell. If you imagine yourself in such a situation, what
> would your explanation be? I don't think that "we decided to make it
> compatible with realpath(3)" quite cuts it. But this is just my personal
> opinion, of course (and, FWIW, I don't think I personally have any script
> which could be broken by this change anyhow).
> 
> Regards,
> VZ