Re: [Emacs-diffs] master 4d3a595: `load-path' should contain only directory names

[Stephen Leake <stephen_leake@stephe-leake.org>]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

>> Nothing, except that we can point them to the docs and say that they
>> live dangerously ;-)
>
> So you live dangerously if you forget the trailing slash in
> default-directory, but you live dangerously if you do add it in
> load-path?

Yes, that's what the current implementation provides. I agree it's not
consistent (apparently XEmacs is more consistent here).

> What's the benefit of this pickiness?

When you are writing code that iterates thru load-path, using the
entries for various things (checking that they exist, listing contents),
it helps to know how they are defined.

> Unless there's a real performance advantage (which I fail to see), 

The only performance advantage so far is the difference between:

(expand-file-name file dir)
;; full defensive programming

(concat dir file)
;; assuming the doc string is right, and/or has been verified at a
;; higher level

which is not likely to be significant in code that is reading the actual
disk (that will be the slow part).

> I'd rather go the other way and be more permissive and fix
> default-directory so it also works correctly when it doesn't have a
> trailing slash.

You can't "fix" default-directory; you could change its definition, but
then you would have to fix (or at least verify)_every_ use of it, which
is impossible, since it could be used in everyone's private code.

We are changing the doc string of load-path, but only because it was
inconsistent with the actual implementation in core. It is now consistent.

-- 
-- Stephe