Printer set up. Wrong type argument: listp

Question

I use Emacs 29.3 on an M1 Mac Mini with OS 14.4.1.

I'm trying to set up PS printing. I picked up the name of my printer from lpstat. I copied the following code, verbatim, to my init.el from the Printing Package page on EmacsWiki:

(require 'printing)     ; load printing package
(setq pr-txt-name 'Brother_HL_L8260CDW_series)
(setq pr-txt-printer-alist
      '(Brother_HL_L8260CDW_series "lpr" nil "Brother_HL_L8260CDW_series"))
(setq pr-ps-name 'Brother_HL_L8260CDW_series)
(setq pr-ps-printer-alist
      '(Brother_HL_L8260CDW_series "lpr" nil "-P" "Brother_HL_L8260CDW_series"))
(pr-update-menus t)

Opening Emacs now gives me the error:

Wrong type argument: listp, Brother_HL_L8260CDW_series

Where is this error coming from? I have a very limited understanding of Emacs Lisp, I thought that copying code from a legit source would not lead to errors. I see that the EmacsWiki page was last edited in 2017. Has something changed in the interim?

Answer 1

Even if you have a single printer the value of pr-txt-printer-alist and pr-ps-printer-alist must be a list of lists. Update the code with another set of parentheses

(setq pr-txt-printer-alist
      '((Brother_HL_L8260CDW_series "lpr" nil "Brother_HL_L8260CDW_series")))

and

(setq pr-ps-printer-alist
      '((Brother_HL_L8260CDW_series "lpr" nil "-P" "Brother_HL_L8260CDW_series")))

Answer 2

You ask:

Where is this error coming from?

M-x set-variable RET debug-on-error RET t

Then, when the error is raised you can see the debugger backtrace in buffer *Backtrace*.