refactor: deprecate EMACS2[89]+, NATIVECOMP, MODULES

To reduce redundancy, remove the maintenance hassle that version
constants would impose later on, and rely on built-in
facilities (featurep) more over global variables or doomisms, these
global constants have been deprecated in favor of Emacs "features":

- EMACS28+   -- replace with (> emacs-major-version 27)
- EMACS29+   -- replace with (> emacs-major-version 28)
- NATIVECOMP -- replace with (featurep 'native-compile)
- MODULES    -- replace with (featurep 'dynamic-modules)

(These constants will be formally removed when v3 is released. The IS-*
constants are likely next, but I haven't decided on their substitutes
yet)

I also decided to follow native-compile's example and provide features
for Emacs' system features (since system-configuration-features' docs
outs itself as a poor method to detect features):

- dynamic-modules
- jansson
- native-compile -- this one already exists, but will instead be removed
  if it's non-functional; i.e. (native-comp-available-p) returns nil.

These are now detectable using featurep, which is fast and built-in.

lisp/cli/doctor.el

@@ -67,7 +67,7 @@ in."
                "\t- might depend subtly on upstream packages updates.\n"
                "You might need to unpin packages to get a fix for a specific commit of Emacs, "
                "and you should be ready to downgrade Emacs if something is just not fixable."))
-    (EMACS29+
+    ((> emacs-major-version 28)
      (warn! "Emacs %s detected" emacs-version)
      (explain! "Doom supports this version, but you are living on the edge! "
                "Be prepared for breakages in future versions of Emacs."))
@@ -108,13 +108,12 @@ in."
               "jansson support (i.e. a native JSON library), particularly LSP users. "
               "You must install a prebuilt Emacs binary with this included, or compile "
               "Emacs with the --with-json option."))
-  (when EMACS28+
-    (unless NATIVECOMP
-      (warn! "Emacs was not built with native compilation support")
-      (explain! "Users will see a substantial performance gain by building Emacs with "
-                "native compilation support, availible in emacs 28+."
-                "You must install a prebuilt Emacs binary with this included, or compile "
-                "Emacs with the --with-native-compilation option.")))
+  (unless (featurep 'native-compile)
+    (warn! "Emacs was not built with native compilation support")
+    (explain! "Users will see a substantial performance gain by building Emacs with "
+              "native compilation support, availible in emacs 28+."
+              "You must install a prebuilt Emacs binary with this included, or compile "
+              "Emacs with the --with-native-compilation option."))
 
   (print! (start "Checking for private config conflicts..."))
   (let* ((xdg-dir (concat (or (getenv "XDG_CONFIG_HOME")

lisp/cli/packages.el

@@ -240,7 +240,7 @@ list remains lean."
 
 (defun doom-packages--write-missing-eln-errors ()
   "Write .error files for any expected .eln files that are missing."
-  (when NATIVECOMP
+  (when (featurep 'native-compile)
     (cl-loop for file in doom-packages--eln-output-expected
              for eln-name = (doom-packages--eln-file-name file)
              for eln-file = (doom-packages--eln-output-file eln-name)
@@ -254,7 +254,7 @@ list remains lean."
 
 (defun doom-packages--compile-site-files ()
   "Queue async compilation for all non-doom Elisp files."
-  (when NATIVECOMP
+  (when (featurep 'native-compile)
     (cl-loop with paths = (cl-loop for path in load-path
                                    unless (file-in-directory-p path doom-local-dir)
                                    collect path)
@@ -301,7 +301,7 @@ declaration) or dependency thereof that hasn't already been."
                    (signal 'doom-package-error (list package e))))))
          (progn
            (doom-packages--compile-site-files)
-           (when NATIVECOMP
+           (when (featurep 'native-compile)
              (doom-packages--wait-for-native-compile-jobs)
              (doom-packages--write-missing-eln-errors))
            (print! (success "\033[KInstalled %d packages") (length built)))
@@ -348,7 +348,7 @@ declaration) or dependency thereof that hasn't already been."
                     (and (eq (car-safe build) :not)
                          (setq want-byte-compile (not want-byte-compile)
                                want-native-compile (not want-native-compile)))
-                    (unless NATIVECOMP
+                    (unless (featurep 'native-compile)
                       (setq want-native-compile nil))
                     (and (or want-byte-compile want-native-compile)
                          (or (file-newer-than-file-p repo-dir build-dir)
@@ -365,7 +365,7 @@ declaration) or dependency thereof that hasn't already been."
                 (straight-use-package (intern package))))
          (progn
            (doom-packages--compile-site-files)
-           (when NATIVECOMP
+           (when (featurep 'native-compile)
              (doom-packages--wait-for-native-compile-jobs)
              (doom-packages--write-missing-eln-errors))
            ;; HACK Every time you save a file in a package that straight tracks,
@@ -659,7 +659,7 @@ If ELPA-P, include packages installed with package.el (M-x package-install)."
            (if (not regraft-repos-p)
                (ignore (print! (item "Skipping regrafting")))
              (doom-packages--regraft-repos repos-to-regraft))
-           (when NATIVECOMP
+           (when (featurep 'native-compile)
              (if (not eln-p)
                  (ignore (print! (item "Skipping native bytecode")))
                (doom-packages--purge-eln))))))))

lisp/doom-editor.el

@@ -561,7 +561,7 @@ files, so this replace calls to `pp' with the much faster `prin1'."
        (lambda (button)
          (helpful-variable (button-get button 'apropos-symbol))))))
 
-  (when EMACS29+
+  (when (> emacs-major-version 28)
     ;; REVIEW This should be reported upstream to Emacs.
     (defadvice! doom--find-function-search-for-symbol-save-excursion-a (fn &rest args)
       "Suppress cursor movement by `find-function-search-for-symbol'.
@@ -669,7 +669,7 @@ on."
   ;; Emacs 29 introduced faster long-line detection, so they can afford a much
   ;; larger `so-long-threshold' and its default `so-long-predicate'.
   (if (fboundp 'buffer-line-statistics)
-      (unless NATIVECOMP
+      (unless (featurep 'native-compile)
         (setq so-long-threshold 5000))
     ;; reduce false positives w/ larger threshold
     (setq so-long-threshold 400)

lisp/doom-packages.el

@@ -110,7 +110,7 @@ uses a straight or package.el command directly).")
 ;;
 ;;; native-comp
 
-(when NATIVECOMP
+(when (featurep 'native-compile)
   (after! comp
     ;; HACK Disable native-compilation for some troublesome packages
     (mapc (doom-partial #'add-to-list 'native-comp-deferred-compilation-deny-list)

lisp/doom-ui.el

@@ -307,7 +307,7 @@ windows, switch to `doom-fallback-buffer'. Otherwise, delegate to original
 (setq resize-mini-windows 'grow-only)
 
 ;; Typing yes/no is obnoxious when y/n will do
-(if EMACS28+
+(if (boundp 'use-short-answers)
     (setq use-short-answers t)
   ;; DEPRECATED Remove when we drop 27.x support
   (advice-add #'yes-or-no-p :override #'y-or-n-p))
@@ -513,7 +513,7 @@ windows, switch to `doom-fallback-buffer'. Otherwise, delegate to original
 ;; Fix #2742: cursor is off by 4 characters in `artist-mode'
 ;; REVIEW Reported upstream https://debbugs.gnu.org/cgi/bugreport.cgi?bug=43811
 ;; DEPRECATED Fixed in Emacs 28; remove when we drop 27 support
-(unless EMACS28+
+(unless (> emacs-major-version 27)
   (add-hook 'artist-mode-hook #'doom-disable-line-numbers-h))
 
 

lisp/doom.el

@@ -77,17 +77,37 @@
 ;;
 ;;; Global constants
 
-;; Emacs features
-(defconst EMACS28+    (> emacs-major-version 27))
-(defconst EMACS29+    (> emacs-major-version 28))
-(defconst MODULES     (bound-and-true-p module-file-suffix))
-(defconst NATIVECOMP  (if (fboundp 'native-comp-available-p) (native-comp-available-p)))
-
-;; Operating system
+;; DEPRECATED
 (defconst IS-MAC      (eq system-type 'darwin))
 (defconst IS-LINUX    (eq system-type 'gnu/linux))
 (defconst IS-WINDOWS  (memq system-type '(cygwin windows-nt ms-dos)))
-(defconst IS-BSD      (or IS-MAC (eq system-type 'berkeley-unix)))
+(defconst IS-BSD      (memq system-type '(darwin berkeley-unix gnu/kfreebsd)))
+
+(unless (featurep 'doom)
+  ;; Since `system-configuration-features's docs state not to rely on it to test
+  ;; for features, let's give users an easier way to detect them.
+  (if (bound-and-true-p module-file-suffix)
+      (push 'dynamic-modules features))
+  (if (fboundp #'json-parse-string)
+      (push 'jansson features))
+  ;; `native-compile' exists whether or not it is functional (e.g. libgcc is
+  ;; available or not). This seems silly, so pretend it doesn't exist if it
+  ;; isn't available.
+  (if (featurep 'native-compile)
+      (if (not (native-comp-available-p))
+          (delq 'native-compile features)))
+
+  ;; DEPRECATED remove in v3
+  (defconst EMACS28+    (> emacs-major-version 27))
+  (defconst EMACS29+    (> emacs-major-version 28))
+  ;; DEPRECATED remove in v3
+  (defconst MODULES     (featurep 'dynamic-modules))
+  (defconst NATIVECOMP  (featurep 'native-compile))
+
+  (make-obsolete-variable 'EMACS28+   "Use (>= emacs-major-version 28) instead" "3.0.0")
+  (make-obsolete-variable 'EMACS29+   "Use (>= emacs-major-version 29) instead" "3.0.0")
+  (make-obsolete-variable 'MODULES    "Use (featurep 'dynamic-modules) instead" "3.0.0")
+  (make-obsolete-variable 'NATIVECOMP "Use (featurep 'native-compile) instead" "3.0.0"))
 
 
 ;;
@@ -291,7 +311,7 @@ users).")
 ;;
 ;;; Native Compilation support (http://akrl.sdf.org/gccemacs.html)
 
-(when NATIVECOMP
+(when (featurep 'native-compile)
   ;; Don't store eln files in ~/.emacs.d/eln-cache (where they can easily be
   ;; deleted by 'doom upgrade').
   (add-to-list 'native-comp-eln-load-path (file-name-concat doom-cache-dir "eln/")))

modules/editor/evil/config.el

@@ -53,7 +53,7 @@ directives. By default, this only recognizes C directives.")
         evil-undo-system
         (cond ((featurep! :emacs undo +tree) 'undo-tree)
               ((featurep! :emacs undo) 'undo-fu)
-              (EMACS28+ 'undo-redo)))
+              ((> emacs-major-version 27) 'undo-redo)))
 
   ;; Slow this down from 0.02 to prevent blocking in large or folded buffers
   ;; like magit while incrementally highlighting matches.

modules/editor/evil/init.el

@@ -136,7 +136,7 @@ variable for an explanation of the defaults (in comments). See
       elisp-slime-nav
       embark
       emms
-      ,@(when EMACS29+ '(emoji))
+      ,@(if (> emacs-major-version 28) '(emoji))
       epa
       ert
       eshell
@@ -226,7 +226,7 @@ variable for an explanation of the defaults (in comments). See
       scroll-lock
       selectrum
       sh-script
-      ,@(when EMACS28+ '(shortdoc))
+      ,@(if (> emacs-major-version 27) '(shortdoc))
       simple
       simple-mpc
       slime

modules/emacs/vc/autoload/bug-reference-backport.el

@@ -1,5 +1,5 @@
 ;;; emacs/vc/autoload/bug-reference-backport.el -*- lexical-binding: t; -*-
-;;;###if (not EMACS28+)
+;;;###if (< emacs-major-version 28)
 ;; DEPRECATED Remove when Emacs 27.x support is dropped
 
 ;; In Emacs 28, the built-in bug-reference package started consulting vc for

modules/term/eshell/autoload/backport.el

@@ -1,5 +1,5 @@
 ;;; term/eshell/autoload/mode.el -*- lexical-binding: t; -*-
-;;;###if (not EMACS28+)
+;;;###if (< emacs-major-version 28)
 
 ;; DEPRECATED Remove this when we drop Emacs 27 support.
 

modules/term/vterm/config.el

@@ -1,7 +1,7 @@
 ;;; term/vterm/config.el -*- lexical-binding: t; -*-
 
 (use-package! vterm
-  :when (bound-and-true-p module-file-suffix)
+  :when (featurep 'dynamic-modules)
   :commands vterm-mode
   :hook (vterm-mode . doom-mark-buffer-as-real-h)
   :hook (vterm-mode . hide-mode-line-mode) ; modeline serves no purpose in vterm

modules/ui/ligatures/config.el

@@ -179,7 +179,7 @@ and cannot run in."
 
  ;; Harfbuzz and Mac builds do not need font-specific ligature support
  ;; if they are above emacs-27.
- ((and EMACS28+
+ ((and (> emacs-major-version 27)
        (or (featurep 'ns)
            (string-match-p "HARFBUZZ" system-configuration-features))
        (featurep 'composite))  ; Emacs loads `composite' at startup