fix: freezing+side-effects on M-x or C-h {f,v}

To understand this issue, you have to understand these two things:

1. Doom builds an init file which combines all its autoloads (for
   packages and modules), and Doom's bootstrapper (which loads modules,
   $DOOMDIR, etc). This init file is byte-compiled.

2. When Emacs byte-compiles elisp, docstrings are lazy-loaded (by
   embedding them in the elc as commented text to be retrieved later).
   This is generally done to save on memory.

Now the issue: when these lazy-loaded docstrings are retrieved, Emacs
may evaluate the whole file to find it, including Doom's bootstrap
process, reloading all its files, the user's config files, and running
all its startup hooks. Not only is this terribly expensive, reloading
these files may have disastrous effects.

One such effect is compounded by Marginalia, which invokes this
docstring fetch process (by calling the `documentation` function in
`marginalia--function-doc`) for *each* symbol in the `M-x` or `C-h
{v,f}` completion lists, which means Doom re-bootstraps multiple times
and rapidly, causing Emacs to totally lock up.

The solution is to simply gate the expensive part of the initfile so it
doesn't run more than once, at startup, and when `doom/reload` is
called. The rest of the file loads instantly.

Still, this is a bit flimsy. I'll think of a more elegant solution
later.

lisp/doom-profiles.el

@@ -369,7 +369,16 @@ Defaults to the profile at `doom-profile-default'."
   (let ((v (version-to-list doom-version))
         (ref (doom-call-process "git" "-C" (doom-path doom-emacs-dir) "rev-parse" "HEAD"))
         (branch (doom-call-process "git" "-C" (doom-path doom-emacs-dir) "branch" "--show-current")))
-    `(,@(cl-loop for var in doom-autoloads-cached-vars
+    ;; FIX: The `doom-init-time' guard protects us from a nefarious edge case in
+    ;;   which Emacs' interpreter, while lazy-loading docstrings in
+    ;;   byte-compiled elisp, ends up re-evaluating the whole file. This can
+    ;;   happen rapidly, multiple times, if something loads these docstrings (by
+    ;;   calling the `documentation' function) rapidly, which is the case for
+    ;;   `marginalia' and each symbol in the M-x and describe-* command
+    ;;   completion lists. By guarding the expensive part of this file, this
+    ;;   process becomes instant.
+    `((unless doom-init-time
+        ,@(cl-loop for var in doom-autoloads-cached-vars
                    if (boundp var)
                    collect `(set-default ',var ',(symbol-value var)))
         (setplist 'doom-version
@@ -378,12 +387,15 @@ Defaults to the profile at `doom-profile-default'."
                     build  ,(nth 2 v)
                     tag    ,(cadr (split-string doom-version "-" t))
                     ref    ,(if (zerop (car ref)) (cdr ref))
-                  branch ,(if (zerop (car branch)) (cdr branch)))))))
+                    branch ,(if (zerop (car branch)) (cdr branch))))))))
 
 (defun doom-profile--generate-load-modules ()
-  (let ((module-list (cddr (doom-module-list))))
+  (let ((module-list (doom-module-list)))
-    `((set 'doom-disabled-packages ',doom-disabled-packages)
+    ;; FIX: Same as above (see `doom-profile--generate-init-vars').
+    `((unless doom-init-time
+        (set 'doom-disabled-packages ',doom-disabled-packages)
         (set 'doom-modules ',doom-modules)
+        (defvar doom-modules-list ',(cddr module-list))
         ;; Cache module state and flags in symbol plists for quick lookup by
         ;; `modulep!' later.
         ,@(cl-loop for (category . modules) in (seq-group-by #'car (doom-module-list))
@@ -414,7 +426,7 @@ Defaults to the profile at `doom-profile-default'."
         (let ((old-custom-file custom-file))
           (doom-load ,(doom-path doom-user-dir doom-module-config-file) 'noerror)
           (when (eq custom-file old-custom-file)
-          (doom-load custom-file 'noerror))))))
+            (doom-load custom-file 'noerror)))))))
 
 (defun doom-profile--generate-doom-autoloads ()
   (doom-autoloads--scan

lisp/doom-start.el

@@ -358,7 +358,12 @@ If RETURN-P, return the message as a string instead of displaying it."
                    ;; Compiling them in one place is a big reduction in startup
                    ;; time, and by keeping a history of them, you get a snapshot
                    ;; of your config in time.
-                   (file-name-concat doom-profile-dir (format "init.%d.elc" emacs-major-version))))
+                   (file-name-concat
+                    doom-profile-dir (format "init.%d.elc" emacs-major-version)))
+                  ;; If the config is being reloaded, let's pretend it hasn't be
+                  ;; initialized by unsetting this (see note in
+                  ;; `doom-profile--generate-load-modules' for details).
+                  doom-init-time)
               ;; If `user-init-file' is t, then `load' will store the name of
               ;; the file that it loads into `user-init-file'.
               (setq user-init-file t)