Re: [PATCH] Re: Parser issues and and [[ $var ]]

[Peter Stephenson <p.stephenson@samsung.com>]

On Mon, 12 May 2014 22:01:12 -0700
Bart Schaefer <schaefer@brasslantern.com> wrote:
> This problem already exists -- infix operators that aren't tokens like
> && and || are already lower prececence than prefix operators.  E.g.:
> 
> zsh% [[ -n 1 -eq 1 ]]
> zsh: unknown condition: -n
> 
> So I don't think the patch below changes any of that.

While this sort of thing and the problems with modular conditions are a
real headache for parsing, I don't think the actual practical problems
are anything like as bad.  Almost always real tests use parameters or
quoted expressions (you don't need to know if the literal string -n has
non-zero length), and since [[, unlike [, is parsed before expansion
such tests work fine.  About the only likely exception I can think of is
where someone's used an eval to get an extra level of expansion --- but
that's always a bit hairy.

So having addressed the compatibility issues, perhaps we should restrict
ourselves to tweaking the documentation to mention the problems and how
to keep them at bay.

pws