Prioritize private snippets over built-in ones

In the case of snippet conflicts, you'd normally be prompted to select
which snippet you want. Built-in snippets are now disregarded if
conflicting private ones exist.

This makes it easier for users to add overriding snippets to
DOOMDIR/snippets.

modules/feature/snippets/autoload/snippets.el

@@ -1,8 +1,20 @@
 ;;; feature/snippets/autoload/snippets.el -*- lexical-binding: t; -*-
 
-;;
+;;;###autoload
-;; Commands
+(defun +snippets-prompt-private (prompt choices &optional fn)
-;;
+  "Prioritize private snippets (in `+snippets-dir') over built-in ones if there
+are multiple choices."
+  (when-let*
+      ((choices
+        (or (cl-loop for tpl in choices
+                     if (file-in-directory-p (yas--template-get-file tpl)
+                                             +snippets-dir)
+                     collect tpl)
+            choices)))
+    (if (cdr choices)
+        (let ((prompt-functions (remq '+snippets-prompt-private yas-prompt-functions)))
+          (run-hook-with-args-until-success 'prompt-functions prompt choices fn))
+      (car choices))))
 
 ;;;###autoload
 (defun +snippets/goto-start-of-field ()

modules/feature/snippets/config.el

@@ -22,11 +22,17 @@
   :config
   (setq yas-verbosity (if doom-debug-mode 3 0)
         yas-also-auto-indent-first-line t
-        yas-prompt-functions (delq #'yas-dropdown-prompt yas-prompt-functions)
         yas-triggers-in-field t)  ; Allow nested snippets
 
+  ;; Allow private snippets in DOOMDIR/snippets
   (add-to-list 'yas-snippet-dirs '+snippets-dir nil #'eq)
 
+  ;; Remove GUI dropdown prompt (prefer ivy/helm)
+  (delq #'yas-dropdown-prompt yas-prompt-functions)
+  ;; Prioritize private snippets in `+snippets-dir' over built-in ones if there
+  ;; are multiple choices.
+  (add-to-list 'yas-prompt-functions #'+snippets-prompt-private nil #'eq)
+
   ;; Register `def-project-mode!' modes with yasnippet. This enables project
   ;; specific snippet libraries (e.g. for Laravel, React or Jekyll projects).
   (add-hook 'doom-project-hook #'+snippets|enable-project-modes)