* bug#4819: file-truename's undocumented behavior
@ 2009-10-28 0:28 MON KEY
2009-10-28 1:52 ` Stefan Monnier
0 siblings, 1 reply; 7+ messages in thread
From: MON KEY @ 2009-10-28 0:28 UTC (permalink / raw)
To: bug-gnu-emacs
This form returns a value.
(file-truename "")
WHY?
I just spent 2 1/2 hours in a break-loop three functions away trying to debug
_undocumented_ behavior.
GNU Emacs 23.1.50.1 (i386-mingw-nt5.1.2600)
of 2009-06-30 on LENNART-69DE564 (patched)
^ permalink raw reply [flat|nested] 7+ messages in thread
* bug#4819: file-truename's undocumented behavior
2009-10-28 0:28 bug#4819: file-truename's undocumented behavior MON KEY
@ 2009-10-28 1:52 ` Stefan Monnier
2009-10-28 20:01 ` MON KEY
0 siblings, 1 reply; 7+ messages in thread
From: Stefan Monnier @ 2009-10-28 1:52 UTC (permalink / raw)
To: MON KEY; +Cc: 4819, bug-gnu-emacs
> This form returns a value.
> (file-truename "")
> WHY?
Why not? What value did you expect?
> I just spent 2 1/2 hours in a break-loop three functions away trying
> to debug _undocumented_ behavior.
Which part of the documentation do you think this behavior contradicts?
Stefan
^ permalink raw reply [flat|nested] 7+ messages in thread
* bug#4819: file-truename's undocumented behavior
2009-10-28 1:52 ` Stefan Monnier
@ 2009-10-28 20:01 ` MON KEY
2009-10-29 0:37 ` Stefan Monnier
0 siblings, 1 reply; 7+ messages in thread
From: MON KEY @ 2009-10-28 20:01 UTC (permalink / raw)
To: Stefan Monnier; +Cc: 4819, bug-gnu-emacs
[-- Attachment #1: Type: text/plain, Size: 5480 bytes --]
On Tue, Oct 27, 2009 at 9:52 PM, Stefan Monnier
<monnier@iro.umontreal.ca> wrote:
>> This form returns a value.
>> (file-truename "")
>
>> WHY?
>
> Why not? What value did you expect?
I assumed nil.
I'm not sure what I would expect esp. having since noted that:
(file-relative-name "") ;=> "."
(file-exists-p "") ;=> t
(file-readable-p "") ;=> t
(file-directory-p "") ;=> t
(file-name-as-directory "") ;=> "./"
However, discarding the state of my "least surprisedness", I would _not_ expect
that file-truename would step all over the match-data, and where it does so not
before first:
a) Using string-match-p where applicable;
b) Noting that it does so in the documention. i.e. as per `split-string'.
>
>> I just spent 2 1/2 hours in a break-loop three functions away trying
>> to debug _undocumented_ behavior.
>
> Which part of the documentation do you think this behavior contradicts?
>
This part:
(file-name-absolute-p "") ;=> nil
(file-symlink-p "") ;=> nil
On which systems/platforms does "" denote an absolute filename?
On which systems/platforms does "" denote a symbolic link for a filename?
,---- (documentation 'file-truename)
| Return the truename of filename, which should be absolute.
| The truename of a file name is found by chasing symbolic links
| both at the level of the file and at the level of the directories
| containing it, until no links are left at any level.
`----
And, this other part where documentation:
a) Neglects to mention that this function invokes repeatedly invokes
`string-match' twice per invokation.
{...} (unless (string-match "[[*?]" filename)
(string-match "~[^/]*/?" filename)) {...}
{...} ((and (string= (substring filename 0 1) "~")
(string-match "~[^/]*/?" filename)) {...}
b) Neglects to mention that the remaining args COUNTER and PREV-DIRS are
iterative counters for operations on recursive calls. Which means that where
file-truename recurses `string-match' may be invoked more than twice times.
,---- Comments in the definition of `file-truename' in files.el
|;; Don't document the optional arguments.
|;; COUNTER and PREV-DIRS are only used in recursive calls.
|;; COUNTER can be a cons cell whose car is the count of how many
|;; more links to chase before getting an error.
|;; PREV-DIRS can be a cons cell whose car is an alist
|;; of truenames we've just recently computed.
`----
It was only as a late afterthought that I realized that it wasn't _MY-CODE+
clobbering the match-data - as is usual : ) but maybe Emacs'. The realization
was elusive because the recursion only happens when the w32 conditional which
drops into a recursion predicated on the return value of `w32-long-file-name'.
{...} (setq filename (concat (file-truename rest) missing)) {...}
Why not mention in the docs that on w32 `w32-long-file-name' may be a more
suitable alternative esp. as it is a primitive and as it will expand "8.3 DOS"
short name aliases in the process. (Again, per _existing_ comments in body of
`file-truename's definition).
I understand _why_ the optional args have been left undocumented - they are
essentially hacks which the user shouldn't rely on. However, I don't understand
_why_ the w32 hack isn't made known esp. where the hack is applicable for user
code and is indicated as the preferred solution...
W/re the string-match vs. string-matchp doesn't the following accomplish the
same:
;;; ==============================
*** /files.el-p 2009-10-28 15:49:38.843750000 -0400
--- /emacs/lisp/files.el 2009-06-30 15:51:22.000000000 -0400
***************
*** 893,904 ****
(setq filename (expand-file-name filename))
(if (string= filename "")
(setq filename "/")))
! ((and (string= (substring filename 0 1) "~")
! (string-match-p "~[^/]*/?" filename))
! (string-match "~[^/]*/?" filename)
! (let ((first-part
! (substring filename 0 (match-end 0)))
! (rest (substring filename (match-end 0))))
(setq filename (concat (expand-file-name first-part) rest)))))
(or counter (setq counter (list 100)))
--- 893,903 ----
(setq filename (expand-file-name filename))
(if (string= filename "")
(setq filename "/")))
! ((and (string= (substring filename 0 1) "~")
! (string-match "~[^/]*/?" filename))
! (let ((first-part
! (substring filename 0 (match-end 0)))
! (rest (substring filename (match-end 0))))
(setq filename (concat (expand-file-name first-part) rest)))))
(or counter (setq counter (list 100)))
***************
*** 930,936 ****
(if handler
(setq filename (funcall handler 'file-truename filename))
;; If filename contains a wildcard, newname will be the old name.
! (unless (string-match-p "[[*?]" filename)
;; If filename exists, use the long name. If it doesn't exist,
;; drill down until we find a directory that exists, and use
;; the long name of that, with the extra non-existent path
--- 929,935 ----
(if handler
(setq filename (funcall handler 'file-truename filename))
;; If filename contains a wildcard, newname will be the old name.
! (unless (string-match "[[*?]" filename)
;; If filename exists, use the long name. If it doesn't exist,
;; drill down until we find a directory that exists, and use
;; the long name of that, with the extra non-existent path
[-- Attachment #2: diff.files.el --]
[-- Type: application/octet-stream, Size: 2002 bytes --]
*** /files.el-p 2009-10-28 15:49:38.843750000 -0400
--- /emacs/lisp/files.el 2009-06-30 15:51:22.000000000 -0400
***************
*** 893,904 ****
(setq filename (expand-file-name filename))
(if (string= filename "")
(setq filename "/")))
! ((and (string= (substring filename 0 1) "~")
! (string-match-p "~[^/]*/?" filename))
! (string-match "~[^/]*/?" filename)
! (let ((first-part
! (substring filename 0 (match-end 0)))
! (rest (substring filename (match-end 0))))
(setq filename (concat (expand-file-name first-part) rest)))))
(or counter (setq counter (list 100)))
--- 893,903 ----
(setq filename (expand-file-name filename))
(if (string= filename "")
(setq filename "/")))
! ((and (string= (substring filename 0 1) "~")
! (string-match "~[^/]*/?" filename))
! (let ((first-part
! (substring filename 0 (match-end 0)))
! (rest (substring filename (match-end 0))))
(setq filename (concat (expand-file-name first-part) rest)))))
(or counter (setq counter (list 100)))
***************
*** 930,936 ****
(if handler
(setq filename (funcall handler 'file-truename filename))
;; If filename contains a wildcard, newname will be the old name.
! (unless (string-match-p "[[*?]" filename)
;; If filename exists, use the long name. If it doesn't exist,
;; drill down until we find a directory that exists, and use
;; the long name of that, with the extra non-existent path
--- 929,935 ----
(if handler
(setq filename (funcall handler 'file-truename filename))
;; If filename contains a wildcard, newname will be the old name.
! (unless (string-match "[[*?]" filename)
;; If filename exists, use the long name. If it doesn't exist,
;; drill down until we find a directory that exists, and use
;; the long name of that, with the extra non-existent path
^ permalink raw reply [flat|nested] 7+ messages in thread
* bug#4819: file-truename's undocumented behavior
2009-10-28 20:01 ` MON KEY
@ 2009-10-29 0:37 ` Stefan Monnier
2009-10-29 0:56 ` Lennart Borgman
` (2 more replies)
0 siblings, 3 replies; 7+ messages in thread
From: Stefan Monnier @ 2009-10-29 0:37 UTC (permalink / raw)
To: MON KEY; +Cc: 4819, bug-gnu-emacs
> I assumed nil.
That would be very unexpected, since file-truename otherwise always
returns a string when passed a string.
> However, discarding the state of my "least surprisedness", I would
> _not_ expect that file-truename would step all over the match-data,
> and where it does so not before first:
Most functions don't preserve the match-data, and even more so for
functions that manipulate strings or buffers.
> b) Noting that it does so in the documention. i.e. as per `split-string'.
It's the other way around: the few functions that preserve the
match-data should be documented as such (better yet: the byte-compiler
should be taught about them, so it can detect when we use the
match-data after it got clobbered).
>>> I just spent 2 1/2 hours in a break-loop three functions away trying
>>> to debug _undocumented_ behavior.
>> Which part of the documentation do you think this behavior contradicts?
> This part:
> (file-name-absolute-p "") ;=> nil
> (file-symlink-p "") ;=> nil
That's not a part of the documentation.
> Why not mention in the docs that on w32 `w32-long-file-name' may be
> a more suitable alternative esp. as it is a primitive and as it will
> expand "8.3 DOS" short name aliases in the process. (Again, per
> _existing_ comments in body of `file-truename's definition).
Elisp should generally not be w32-specific, so ratehr than use
w32-long-file-name we should maybe change
file-truename correspondingly. That doesn't mean I think it's the right
thing to do: I know next to nothing about this issue.
> ! ((and (string= (substring filename 0 1) "~")
> ! (string-match-p "~[^/]*/?" filename))
> ! (string-match "~[^/]*/?" filename)
> ! (let ((first-part
> ! (substring filename 0 (match-end 0)))
> ! (rest (substring filename (match-end 0))))
What's the point? If you're going to use string-match in the end, you
might as well do it right away.
Stefan
^ permalink raw reply [flat|nested] 7+ messages in thread
* bug#4819: file-truename's undocumented behavior
2009-10-29 0:37 ` Stefan Monnier
@ 2009-10-29 0:56 ` Lennart Borgman
2009-11-07 0:01 ` MON KEY
2011-07-09 5:51 ` Glenn Morris
2 siblings, 0 replies; 7+ messages in thread
From: Lennart Borgman @ 2009-10-29 0:56 UTC (permalink / raw)
To: Stefan Monnier, 4819; +Cc: bug-gnu-emacs, MON KEY
On Thu, Oct 29, 2009 at 1:37 AM, Stefan Monnier
<monnier@iro.umontreal.ca> wrote:
>
>> Why not mention in the docs that on w32 `w32-long-file-name' may be
>> a more suitable alternative esp. as it is a primitive and as it will
>> expand "8.3 DOS" short name aliases in the process. (Again, per
>> _existing_ comments in body of `file-truename's definition).
>
> Elisp should generally not be w32-specific, so ratehr than use
> w32-long-file-name we should maybe change
> file-truename correspondingly. That doesn't mean I think it's the right
> thing to do: I know next to nothing about this issue.
It already calls w32-long-file-name. (I am not sure what MON means.)
^ permalink raw reply [flat|nested] 7+ messages in thread
* bug#4819: file-truename's undocumented behavior
2009-10-29 0:37 ` Stefan Monnier
2009-10-29 0:56 ` Lennart Borgman
@ 2009-11-07 0:01 ` MON KEY
2011-07-09 5:51 ` Glenn Morris
2 siblings, 0 replies; 7+ messages in thread
From: MON KEY @ 2009-11-07 0:01 UTC (permalink / raw)
To: Stefan Monnier; +Cc: 4819, bug-gnu-emacs
Stefan,
I'm very sorry for the delayed response things have been hectic of late.
On Wed, Oct 28, 2009 at 7:37 PM, Stefan Monnier
<monnier@iro.umontreal.ca> wrote:
>> I assumed nil.
>
> That would be very unexpected, since file-truename otherwise always
> returns a string when passed a string.
Yes, understood; most likely my assumptions are predicated by these seemingly
contradictory behaviors:
(file-name-absolute-p "") ;=> nil
(file-symlink-p "") ;=> nil
>
> It's the other way around: the few functions that preserve the
> match-data should be documented as such (better yet: the byte-compiler
> should be taught about them, so it can detect when we use the
> match-data after it got clobbered).
No argument there :)
>>> Which part of the documentation do you think this behavior contradicts?
>
>> This part:
>> (file-name-absolute-p "") ;=> nil
>> (file-symlink-p "") ;=> nil
>
> That's not a part of the documentation.
You're right. None the less, this behaviour does contradict behaviour indicated
by said docs.
> Elisp should generally not be w32-specific, so ratehr than use
> w32-long-file-name we should maybe change
> file-truename correspondingly. That doesn't mean I think it's the right
> thing to do: I know next to nothing about this issue.
Best I can gather the existing w32 conditional branch has been around for a long
time. i.e. the email address in the comments carry a {...}@harlequin.co.uk
domain.
>
>> ! ((and (string= (substring filename 0 1) "~")
>> ! (string-match-p "~[^/]*/?" filename))
>> ! (string-match "~[^/]*/?" filename)
>> ! (let ((first-part
>> ! (substring filename 0 (match-end 0)))
>> ! (rest (substring filename (match-end 0))))
>
> What's the point?
To avoid setting the match-data b/c it _is not_ necessarily going to be used per
the conditional.
> If you're going to use string-match in the end, you might as well do it right
> away.
This is wrong.
Though, it may explain how/why the existing situation persists :)
> Stefan
>
s_P
^ permalink raw reply [flat|nested] 7+ messages in thread
* bug#4819: file-truename's undocumented behavior
2009-10-29 0:37 ` Stefan Monnier
2009-10-29 0:56 ` Lennart Borgman
2009-11-07 0:01 ` MON KEY
@ 2011-07-09 5:51 ` Glenn Morris
2 siblings, 0 replies; 7+ messages in thread
From: Glenn Morris @ 2011-07-09 5:51 UTC (permalink / raw)
To: 4819-done
I don't see a need to keep open this particular report, which was marked
"wontfix" some time ago.
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2011-07-09 5:51 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2009-10-28 0:28 bug#4819: file-truename's undocumented behavior MON KEY
2009-10-28 1:52 ` Stefan Monnier
2009-10-28 20:01 ` MON KEY
2009-10-29 0:37 ` Stefan Monnier
2009-10-29 0:56 ` Lennart Borgman
2009-11-07 0:01 ` MON KEY
2011-07-09 5:51 ` Glenn Morris
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