Proposal to add :use keyword to layer declaration

[sooheon]

In the spirit of being explicit about what you would like to use, rather than excluding what you don't want, a :use keyword for the dotspacemacs-configuration-layers list would be useful.

Specifically for adding on to spacemacs-base, currently the layers like spacemacs-ui spacemacs-evil etc. still come whole hog, and you end up adding most of spacemacs default back if you want something in the layers. This would allow you to be more selective, more easily.

'(better-defaults
  (spacemacs-ui :use '(info+ window-numbering))
  clojure)

[a13ph]

I suggest keyword "only" instead of "use".
In my opinion it is much more self-evident that "only" those packages are used, rather than additionally or selected from some optional ones (like choosing backend, for example).
However, if it's used somewhere else (use-package?) extensively and therefore will be more consistent, I'll retract

[sooheon]

I agree :only is more clear about the meaning.

[sooheon]

:exclude as a layer argument may also make sense, because this keeps layers atomic, rather than putting the exclusions in a dotspacemacs variable, which can fall out of sync with the actual layers I'm using.

[a13ph]

@sooheon I very much agree on the :exclude proposition too. Global exclusion has it's merits, but it's not in line with layer way.

[justbur]

If I could add to this, I like the idea of having the ability to include or exclude packages but not the separate keywords because then you need to specify rules about what happens when both are used. If the choice were mine, I think I'd do something like this

  (spacemacs-ui :packages (info+ window-numbering))
  (spacemacs-ui-visual :packages (not neotree))

[syl20bnr]

👍 to @justbur's proposal.

[sooheon]

If I want spacemacs-ui, but just without window-numbering, I think the explicit :exclude will be useful.

(spacemacs-ui :packages '(ace-link
                          ace-window
                          buffer-move
                          (centered-cursor :location local)
                          desktop
                          (doc-view :location built-in)
                          flx-ido
                          info+
                          open-junk-file)

(spacemacs-ui :exclude '(window-numbering))

The rules for both being used should not be complicated, and it should be no different than if someone has defined :packages for a layer, and excluded some other package used by that layer globally, so we need to hash out the precedence anyway. I'm leaning toward :exclude taking precedence, if we see current layer declarations as implicit :use for all its packages.

The benefit is that we gain atomicity for layer declarations, as said before. I don't need to include a whole layer, then exclude bits of it globally, which is brittle.

[justbur]

@sooheon you missed that I had a not at the head of the list in the second example. The idea was that :packages (not ...) would exclude packages.

[sooheon]

@justbur I did! That was much more elegant than what I had thought. Scratch my proposal above, yours is much improved.

[github-actions]

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