Add notes on use-package

1 files changed, 48 insertions, 0 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