Add notes on use-package

2 files changed, 67 insertions, 14 deletions

diff --git a/guides/emacs/use-package.org b/guides/emacs/use-package.org
new file mode 100644
index 0000000..f6cd027
--- /dev/null
+++ b/guides/emacs/use-package.org
@@ -0,0 +1,48 @@
+* Porting from ~custom-file~
+Some very dumb code to generate ~use-package~ declarations from Custom
+settings.  Entry point is ~c->us/port~.
+#+begin_src elisp
+(require 'help-fns)
+(require 'radix-tree)
+
+(defun c->us/get-custom-options ()
+  (seq-map
+   (pcase-lambda (`(theme-value ,option user ,value))
+     (list option value))
+   (get 'user 'theme-settings)))
+
+(defun c->us/get-option-file (option)
+  ;; Load packages first, otherwise symbol-file can return "loaddefs".
+  (pcase-dolist
+      (`(_ . ,files)
+       (radix-tree-prefixes (help-definition-prefixes)
+                            (symbol-name option)))
+    (dolist (f files)
+      (load f 'noerror 'nomessage)))
+  (when-let ((file (symbol-file option)))
+    (file-name-base file)))
+
+(defun c->us/write-declaration (lib pairs)
+  (insert (format "(use-package %s\n" lib))
+  (insert "  :custom")
+  (message "%s -> %s" lib pairs)
+  (pcase-dolist
+      (`(,option ,value) pairs)
+    (insert (format "\n  (%s %s)"
+                    option
+                    (prin1-to-string value))))
+  (insert ")\n\n"))
+
+(defun c->us/symbols< (symlist1 symlist2)
+  (string< (car symlist1) (car symlist2)))
+
+(defun c->us/port ()
+  (seq-map
+   (pcase-lambda (`(,lib . ,pairs))
+     (c->us/write-declaration lib pairs))
+   (sort (seq-group-by
+          (pcase-lambda (`(,option _))
+            (c->us/get-option-file option))
+          (sort (c->us/get-custom-options) 'c->us/symbols<))
+         'c->us/symbols<)))
+#+end_src
diff --git a/reviews/emacs/hype.org b/reviews/emacs/hype.org
index 03a54cc..42e9b6a 100644
--- a/reviews/emacs/hype.org
+++ b/reviews/emacs/hype.org
@@ -5,20 +5,25 @@ the changes /I/ am excited about.
 ** =:core= promotions
 A couple of ELPA packages have moved to emacs.git, making them
 available out of the box.
-
-- eglot ("Emacs Polyglot") :: an LSP client that lets Emacs leverage
-  language servers to boost completion-at-point, eldoc, flymake,
-  imenu, project, xref.
-
-- use-package :: a utility macro for configuring packages that makes
-  init-file management more pleasant (and efficient to boot):
-  - OT1H, brings some amount of structure and order when compared to a
-    fully free-form DYI =.emacs=,
-  - OTOH, allows more leeway on how to organize things, when compared
-    to Custom's rigid auto-generated forms (e.g. using regular code
-    comments, computing option values),
-  - takes care of setting up the ~eval-after-load~ wizardry to keep
-    startup snappy.
+*** eglot ("Emacs Polyglot"): LSP client
+Lets Emacs leverage language servers to boost completion-at-point,
+eldoc, flymake, imenu, project, xref.
+*** use-package: init-file management
+A utility macro for configuring packages that makes init-file
+management more pleasant (and efficient to boot):
+
+- OT1H, brings some amount of structure and order when compared to a
+  fully free-form DYI =.emacs=,
+- OTOH, allows more leeway on how to organize things, when compared to
+  Custom's rigid auto-generated forms (e.g. using regular code
+  comments, computing option values, sorting options arbitrarily),
+- takes care of setting up the ~eval-after-load~ wizardry to keep
+  startup snappy.
+
+A tedious aspect of porting a ~custom-file~ to ~use-package~
+declarations is tracking down what package defines which variables,
+since not every variable is named after the package it belongs to.
+I wrote [[file:~/memory-leaks/guides/emacs/use-package.org::*Porting from ~custom-file~][some code to make the process faster]].
 ** ~global-text-scale-adjust~
 ~text-scale-adjust~ (bound to =C-x C-X= ∀ =X= ∈ =[=+-0]=) only scales
 the font size in the current buffer; more often than not, one may want