bug#31317: 26.1; Add a tramp-make-tramp-temp-file* variant which returns the full tramp filename?

bug#31317: 26.1; Add a tramp-make-tramp-temp-file* variant which returns the full tramp filename?

[Phil Sainty]

I have a tramp use-case where I want to create a temporary file
on the remote host and then populate that file via elisp -- I am
using (with-temp-file tramp-file-name (insert contents)) -- and
`tramp-make-tramp-temp-file' doesn't seem to facilitate this
nicely due to it returning only the local part of the generated
filename, which means I need to *recreate* the full tramp path
for that file before I can edit the file.

At present I am using `tramp-make-tramp-file-name' using the
returned local path and the original vector passed to
`tramp-make-tramp-temp-file'; but as well as being cumbersome,
I don't like making the assumption that I'm always going to get
the correct value (even if it turns out that I would in practice).

(I should perhaps even be dissecting the return value of
`tramp-get-remote-tmpdir' to obtain a new vector to recreate
that full path with, but that's even more work, and it looks
like it would wind up being the same values...)

It would seem useful to split `tramp-make-tramp-temp-file' into
two functions; one to generate the temporary file and return the
full path, and the other to return the localname.

Does the following seem reasonable?


(defun tramp-make-tramp-temp-file (vec)
   "Create a temporary file on the remote host identified by VEC.
Return the local name of the temporary file."
   (with-parsed-tramp-file-name (tramp-make-tramp-temp-file* vec)
       nil localname))

(defun tramp-make-tramp-temp-file* (vec)
   "Create a temporary file on the remote host identified by VEC.
Return the full tramp file name of the temporary file."
   (let ((prefix (expand-file-name
                  tramp-temp-name-prefix (tramp-get-remote-tmpdir vec)))
         result)
     (while (not result)
       ;; `make-temp-file' would be the natural choice for
       ;; implementation.  But it calls `write-region' internally,
       ;; which also needs a temporary file - we would end in an
       ;; infinite loop.
       (setq result (make-temp-name prefix))
       (if (file-exists-p result)
           (setq result nil)
         ;; This creates the file by side effect.
         (set-file-times result)
         (set-file-modes result (string-to-number "0700" 8))))
     result))



In GNU Emacs 26.1 (build 1, x86_64-pc-linux-gnu, X toolkit, Xaw3d scroll 
bars)
  of 2018-04-15 built on shodan
Windowing system distributor 'The X.Org Foundation', version 
11.0.11804000
System Description:	Ubuntu 16.04.4 LTS

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
GNU Emacs 26.1 (build 1, x86_64-pc-linux-gnu, X toolkit, Xaw3d scroll 
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uncompressing tramp.el.gz...done
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bug#31317: 26.1; Add a tramp-make-tramp-temp-file* variant which returns the full tramp filename?

[Michael Albinus]

Phil Sainty <psainty@orcon.net.nz> writes:

Hi Phil,

> I have a tramp use-case where I want to create a temporary file
> on the remote host and then populate that file via elisp -- I am
> using (with-temp-file tramp-file-name (insert contents)) -- and
> `tramp-make-tramp-temp-file' doesn't seem to facilitate this
> nicely due to it returning only the local part of the generated
> filename, which means I need to *recreate* the full tramp path
> for that file before I can edit the file.

What about `make-nearby-temp-file'?

Best regards, Michael.

bug#31317: 26.1; Add a tramp-make-tramp-temp-file* variant which returns the full tramp filename?

[Phil Sainty]

On 2018-05-01 01:20, Michael Albinus wrote:
> What about `make-nearby-temp-file'?

Thanks Michael.  I see that this is new to 26.1.

> ** The new functions 'make-nearby-temp-file' and 
> 'temporary-file-directory'
> can be used for creation of temporary files on remote or mounted 
> directories.

That certainly does the trick.

Would it make sense for `tramp-make-tramp-temp-file' to be utilising 
that
function?  (i.e. composing a tramp file name from VEC and then handing 
off
to `make-nearby-temp-file' ?)


-Phil

bug#31317: 26.1; Add a tramp-make-tramp-temp-file* variant which returns the full tramp filename?

[Michael Albinus]

Phil Sainty <psainty@orcon.net.nz> writes:

Hi Phil,

> That certainly does the trick.

Yep, I'm closing this bug.

> Would it make sense for `tramp-make-tramp-temp-file' to be utilising
> that function?  (i.e. composing a tramp file name from VEC and then
> handing off to `make-nearby-temp-file' ?)

No, see the comment inside `tramp-make-tramp-temp-file'.  It must use
`make-temp-name' instead of `make-temp-file'.

> -Phil

Best regards, Michael.

bug#31317: 26.1; Add a tramp-make-tramp-temp-file* variant which returns the full tramp filename?

[Phil Sainty]

On 2018-05-01 02:10, Michael Albinus wrote:
> Phil Sainty <psainty@orcon.net.nz> writes:
>> Would it make sense for `tramp-make-tramp-temp-file' to be utilising
>> that function?  (i.e. composing a tramp file name from VEC and then
>> handing off to `make-nearby-temp-file' ?)
> 
> No, see the comment inside `tramp-make-tramp-temp-file'.  It must use
> `make-temp-name' instead of `make-temp-file'.

I'm rather confused about why there would be a danger of an infinite
loop if `tramp-make-tramp-temp-file' called `make-nearby-temp-file',
if that (presumably) is not a danger if I call `make-nearby-temp-file'
in a tramp context?

I'm obviously missing something.  Never mind.  Thank you for pointing
me to the new function!


-Phil