add package to load-path only when needed

lisp/init-package.el

@@ -0,0 +1,57 @@
+;; -*- coding: utf-8; lexical-binding: t; -*-
+
+(defconst creature/pkg-dir
+  (expand-file-name
+   "../site-lisp"
+   (file-name-directory(or load-file-name buffer-file-name)))
+  "Package directory.")
+
+(require 'cl-lib)
+(require 'subr-x)
+
+(defun add-dir-and-subdirs-to-load-path (dir)
+  "Add directory and its subdirectoris to `load-path'.
+Detect whether there are any loadable module in DIR, if so, add DIR to `load-path'.
+Do this recursively for subdirectories of DIR."
+  (unless (file-directory-p dir)
+    (error "%s is not a directory" dir))
+
+  (let ((subdirs nil)
+        (files nil)
+        (temp-filepath nil)
+        ;; (loadable-suffixes (get-load-suffixes))
+        (load-extension (mapcar (lambda (str) (string-remove-prefix "." str)) load-suffixes))
+        (exclude-dirs '("." ".."
+                        "dist" "node_modules" "__pycache__" "test"
+                        "RCS" "CVS" "rcs" "cvs" ".git" ".github")))
+
+    (dolist (filename (directory-files dir))
+      (setq temp-filepath (file-name-concat dir filename))
+      (if (file-directory-p temp-filepath)
+          (unless (member filename exclude-dirs)
+            (add-to-list 'subdirs temp-filepath t))
+        (when (file-regular-p temp-filepath)
+          (add-to-list 'files temp-filepath t))))
+
+    (when (cl-some (lambda (file)
+                     (member (file-name-extension file) load-extension))
+                   files)
+      (add-to-list 'load-path dir t))
+    (mapc #'add-dir-and-subdirs-to-load-path subdirs)))
+
+(defun add-pkg-in-pkg-dir (pkg)
+  "Add PKG located in `creature/pkg-dir' to `load-path'."
+  (add-dir-and-subdirs-to-load-path (expand-file-name pkg creature/pkg-dir)))
+
+(add-to-list 'load-path creature/pkg-dir t)
+
+;; add basic packages
+(add-pkg-in-pkg-dir "lazy-load")
+
+;; builtin maybe exist
+;; "compat" "transient"
+(dolist (pkg '("compat" "transient"))
+  (unless (locate-library pkg)
+    (add-pkg-in-pkg-dir)))
+
+(provide 'init-package)