How to manually define trusted paths for directory local variables '.dir-locals.el'?

Question

I would like to define a list of trusted paths.

• Where dir-locals.el can be loaded without asking me.
• Without having to be concerned with safe-local-variable-values
  Which isn't very practical if the value contains code which might be edited/modified.

Instead, I would like to have a list of paths, similar to .gitignore, which are "trusted" and won't prompt me to trust expressions.

Answer 1

This can be done by advising hack-local-variables-filter.

(defvar my-trusted-paths
  (list
    "/some/path/"
    "/another/path/"))
(defvar my-trusted-paths-prefix
  (list
    "/another/prefix/"
    "/some/prefix/"))

(defun my-trusted-paths-filter (dir-name)
  (catch 'result
    (dolist (p my-trusted-paths)
      (when (string-equal p dir-name)
        (throw 'result t)))
    (dolist (p my-trusted-paths-prefix)
      (when (string-prefix-p p dir-name)
        (throw 'result t)))))

(advice-add 'hack-local-variables-filter
  :around
  #'
  (lambda (old-fn &rest args)
    (pcase-let ((`(,_variables ,dir-name) args))
      (if (my-trusted-paths-filter dir-name)
        (cl-letf (((symbol-function 'safe-local-variable-p) (lambda (&rest _) t)))
          (apply old-fn args)
          ;; Always accept paths matching.
          t)
        (apply old-fn args)))))

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NOTE: I've since moved to a package that is an alternative to dir-locals that allows out-of-source locals called sidecar-locals.