Re: ada writing guide

[Brian Courtney <bcourtn@hercii.mar.lmco.com>]

Ted Dennison wrote:

> In article <8dhuuu$ou5$1@nnrp1.deja.com>,
>   Robert Dewar <robert_dewar@my-deja.com> wrote:
> > In article <8dhqi7$jv3$1@nnrp1.deja.com>,
> >   Ted Dennison <dennison@telepath.com> wrote:
>
> > T.E.D. seems to be describing a system in which people use
> > neither approach, and merrily destroy one anothers fixes by
> > updating old versions. I would NOT call this version control
> > at all.

Perhaps I can clear things up a bit here.  Teds complaint stems
from the fact that the implementation of  Emacs ada-mode
assumes that each user has their own copy of a special
capitalization exception file (used to overide the default
capitalization rules used by the editor).  If each user has
their own copy, then there is no problem.  Think of it like a
.cshrc file were each user defines their own customized
commands, aliases, etc...).  If a single 'common' file is used
(shared among several users) to ensure that all capitalization
is consistent, there is a chance that changes to the capitalization
exception file can be lost, due to the fact that there is no protection
built into Emacs to detect if someone else has modified the file
since it was last read in.  Whether the file is under configuration
control or not is irrelevant in this situation.   This is a special
configuration file used by the Emacs editor that can be updated
on-the-fly by a user.  Since the implementation of ada-mode
modifies to its "potentialy out of date" internal copy of the exception
file before writting it to disk, someone elses updates to the same file
(made after your Emacs session read the file) can be lost.

Ted was simply giving his opinion on a possible pitfall associated
with using  ada-mode and a *single* capitialization exception file.
I do not believe this is a CM issue.  CM comes into play *after*
the updates have been made to a file.  A CM tool can not prevent
you from accidently deleting lines from a file and then saving them.
CM will, however, allow you to restore the file to the last controlled
version, but all the intermediate changes made outside the CM
tool (while you are still editing the file) are not controlled.   This is
the situtation we are dealing with.

Ted,

There are two possible solutions that I see

 1. make the capitalization file read-only and have the users submit
     changes to the file through the owner.  Not the best solution.

  2. change ada-mode.el to re-read the exception file and update
     the internal copy just before it saves the file.  NOTE: There may
     still be small chance that changes will be lost with this approach,
     but very very unlikely.

     ex,  (NOTE: I have not tried this, but it should work).

from ada-create-case-exception

  ;;  Save the list in the file
  (find-file (expand-file-name ada-case-exception-file))
  (erase-buffer)
  ;; force update of ada-case-exception (reread exception file)
  (ada-case-read-exceptions)   ;; this line added from original
  (mapcar '(lambda (x) (insert (car x) "\n")) ada-case-exception)
  (save-buffer)
  (kill-buffer nil)
  )