Re: Incorporating caching into defgroup/defcustom/defvar for Emacs 25

[Artur Malabarba <bruce.connor.am@gmail.com>]

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On 2 Feb 2015 01:07, "Stephen J. Turnbull" <stephen@xemacs.org> wrote:
>
> Sean Allred writes:
>
>  > Specifically, his point about defcustom is a good one. Such
>  > variables shouldn’t be cached in the same sense.
>
> Why not?  Custom provides a "reset" functionality if the user *wants*
> to reset.  It's not clear to me that a user wouldn't want changes to
> customizable variables to persist.

I wasn't saying defcustoms shouldn't be persistent, I was just saying they
already have a great mechanism for that so they don't need to use this
caching mechanism that is being suggested for internal variables.

Similarly, internal variables can't use the defcustom mechanism (at least,
not without modifications) because (1) they'll show up in the customize
interface and (2) they'll clutter up the user's init file.

>
>  > stash.el was and is designed as a patch for the lack of “internal
>  > persistent variables”. The additional keyword(s?) to defgroup and a
>  > defvar* macro would suffice.
>
> What does stash provide that a session manager such as desktop.el
> doesn't?  That wasn't clear to me from your long email.

With stash, a package can specify that a global variable is supposed to be
persistent, and this variable will automatically be saved/loaded from disk.

I understand desktop.el provides similar functionality, but, IIUC,
desktop.el is more of a user interface. By that I mean sessions are only
saved/loaded if desktop-mode is enabled, and desktop-mode might just be
disabled because the user doesn't want to restore open buffers/files. Some
packages need a way to store persistent data regardless of desktop-mode
(see abbrevs and bookmarks, for instance), and so far they've all been
doing that manually.

Stash provides a simple abstraction for a variable that will be persistent
accross sessions. You just declare a variable to be persistent (Sean
suggested a `defvar*' macro, but I prefer something more specific like
`defstash') and its value will be saved to disk during a session and loaded
from disk at the start of each session (very similar to what desktop.el
does, but without relying on desktop-mode).

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