Convert diff-hl tweaks to use-package

Puzzled by this problem I have with :hook.  "(use-package) Hooks"
suggests that if package X defines function X-foo to be used by
package Y in Y-bar-hook, then the idiomatic thing to do is…

  (use-package X
    :hook ((Y-bar . X-foo)))

… but empirically, if Y.el contains…

  (defcustom Y-bar-hook '(Y-quux Y-corge))
  (add-hook 'Y-bar-hook #'Y-grault)

… then Y-bar-hook will be set to '(X-foo Y-grault): it will be missing
the functions added in the defcustom form.

Since add-hook does this:

  (or (boundp hook) (set hook nil))

I am assuming that the problem happens when use-package runs X's :hook
additions before Y is loaded.  No idea (a) if I can reproduce from -Q
(b) if this is a SNAFU from setting always-defer (c) if this could be
solved by sprinkling :after or :requires.

2 files changed, 33 insertions, 10 deletions

diff --git a/.emacs b/.emacs
index 545218b..af613f3 100644
--- a/.emacs
+++ b/.emacs
@@ -387,9 +387,6 @@
 
 ;;; Version control.
 
-(add-hook 'magit-pre-refresh-hook 'diff-hl-magit-pre-refresh)
-(add-hook 'magit-post-refresh-hook 'diff-hl-magit-post-refresh)
-
 (add-hook 'git-commit-setup-hook 'git-commit-turn-on-flyspell)
 
 (setq magit-process-finish-apply-ansi-colors t)
@@ -456,8 +453,6 @@
   (setq truncate-lines nil)
   (setq-local recenter-positions '(top middle bottom)))
 
-(add-hook 'dired-mode-hook 'diff-hl-dired-mode-unless-remote)
-
 (add-to-list 'ibuffer-saved-filter-groups
              '("my/ibuffer-groups"
                ("REPL"
@@ -683,6 +678,34 @@
              (my/list-update package-archives
                '(("melpa" . "https://melpa.org/packages/")))))
 
+(use-package diff-hl
+  :custom
+  (diff-hl-flydiff-mode t)
+  (global-diff-hl-mode t)
+
+  ;; FIXME: Adding to these hooks _here_ clobbers them, i.e. they end
+  ;; up containing (a) the diff-hl functions (b) whatever functions
+  ;; their libraries add dynamically (c) *none* of the functions
+  ;; included in the defcustom's default value.
+  ;;
+  ;; Therefore, set these hooks up in the :config form _for the
+  ;; libraries that define these hooks_, so that (presumably) the
+  ;; default values for these hooks are loaded *before* adding the
+  ;; diff-hl functions.
+  ;;
+  ;; :hook
+  ;; ((dired-mode . diff-hl-dired-mode-unless-remote)
+  ;;  (magit-pre-refresh . diff-hl-magit-pre-refresh)
+  ;;  (magit-post-refresh . diff-hl-magit-post-refresh))
+  )
+
+(use-package dired
+  :custom
+  (dired-kill-when-opening-new-dired-buffer t)
+  (dired-listing-switches "-al -Fhv --group-directories-first")
+  :config
+  (add-hook 'dired-mode-hook 'diff-hl-dired-mode-unless-remote))
+
 (use-package ediff
   :custom
   (ediff-merge-split-window-function 'split-window-vertically)
@@ -738,7 +761,11 @@
   (magit-define-global-key-bindings nil)
   (magit-diff-refine-hunk t)
   (magit-ediff-dwim-show-on-hunks t)
-  (magit-revision-show-gravatars t))
+  (magit-revision-show-gravatars t)
+  :config
+  ;; See `diff-hl' form for rationale.
+  (add-hook 'magit-pre-refresh-hook 'diff-hl-magit-pre-refresh)
+  (add-hook 'magit-post-refresh-hook 'diff-hl-magit-post-refresh))
 
 (use-package magit-blame
   :delight "👉")
diff --git a/.emacs-custom.el b/.emacs-custom.el
index 8d3b619..11bfaf4 100644
--- a/.emacs-custom.el
+++ b/.emacs-custom.el
@@ -14,9 +14,6 @@
  '(delete-selection-mode t)
  '(describe-bindings-outline t)
  '(diff-default-read-only t)
- '(diff-hl-flydiff-mode t)
- '(dired-kill-when-opening-new-dired-buffer t)
- '(dired-listing-switches "-al -Fhv --group-directories-first")
  '(electric-pair-mode t)
  '(enable-recursive-minibuffers t)
  '(epg-pinentry-mode 'loopback)
@@ -29,7 +26,6 @@
  '(gdb-many-windows t)
  '(generic-extras-enable-list
    '(ansible-inventory-generic-mode etc-fstab-generic-mode etc-modules-conf-generic-mode etc-passwd-generic-mode etc-services-generic-mode etc-sudoers-generic-mode hosts-generic-mode java-manifest-generic-mode java-properties-generic-mode pkginfo-generic-mode prototype-generic-mode resolve-conf-generic-mode x-resource-generic-mode xmodmap-generic-mode))
- '(global-diff-hl-mode t)
  '(global-page-break-lines-mode t nil (page-break-lines))
  '(gnus-cloud-method "nnimap:gmail")
  '(highlight-nonselected-windows t)