After package installation, why Emacs kept retrieving an error message on "Creating directory: Operation not supported" subsequent to normal behavior?

Question

I was using this init file on a NixOS machine.

It is important to note that parts of the file were written with use-package and other parts were a legacy from the classic imperative installation of packages: M-x, package-install, and tweaks on hooks and variables.

This weekend I started a new set-up in a new Macbook Air M1 for professional reasons. I must highlight that I am new to Mac.

As I was trying to make myself at home with Emacs in MacOS, I started to copy small snippets of my old config file and slightly migrate them to mac. As the process was going, I decided to use the opportunity to "code review" my own init file - especially to make it more declarative via use-package. The expectation was to make it more reproducible for future occasions.

Sometimes, especially after creating a declaration of a package not yet installed, there was a weird thing happening. I would receive the following messages on the mini-buffer area:

The funniest point was that after quitting (C-x C-c) and re-starting Emacs, things worked fine (as expected) and the error message would disappear!

And this problem/phenomenon happened multiple times. This is the new config file. See the diff.

Why did this happen? Is the problem related to some specific code snippet? Maybe a reference to a path? Is it related to MacOS?

Now that things work fine and the message is gone, is it possible to reproduce it without installing something new?

Answer 1

Due to security concern, Apple re-designed the file system beginning with High-Sierra version - see this or a little bit more detailed here - so in your settings you have an absolute path starting with the forbidden System.... and you must replace it with the permitted Users/yourname/.emacs.d or whatever you need.

As for errors in warnings window you see - just do package-refresh-contentsand try again to install the package you need.

Answer 2

Ian's and Pedro's propositions seem to do the job, but, IMHO, it's very strange to put this in your init file:

(setq custom-file (locate-user-emacs-file "/home/pedro/.dotfiles/.emacs.d/custom-vars.el"))

since locate-user-emacs-file is supposed to take as argument a file name, not a file path, and has a (not so simple) strategy to find it in the user-emacs-directory (cf. "files.el").

I would rather adapt the user-emacs-directory to the current environment.

Note that the following code could be the same on a macos- or on a linux-based machine.

Since, by default, user-emacs-directory contains "~/.emacs.d", I would change it like this:

(when (file-directory-p "~/.dotfiles")
  (setq user-emacs-directory "~/.dotfiles/.emacs.d"))

And then, you could change the name of your custom file like this:

(setq custom-file (locate-user-emacs-file "custom-vars.el"))

Note that, IMHO, the test with file-directory-p is more robust than the test of the system-configuration:

(setq user-emacs-directory
  (cond
   ((string-match "apple" system-configuration)
    "~/.emacs.d")
   ((string-match "NixOS or whatever ???" system-configuration)
    "~/.dotfiles/.emacs.d")
   (t "~/.emacs.d")))

since a macos computer could actually have a "~/.dotfiles" directory (as a matter of fact, my macs have had a "~/DOT_DIRS" directory since a few decades!)

Answer 3

@Ian was right.

Just to make it even easier for other people to understand it I will post another answer.

This problem originated from the process of bringing an Emacs init file from an old machine (running Linux-based NixOS and with .dotfiles being used) to a new macOS machine (which does not use .dotfiles on the file hierarchy).

Thus, changing my init file from:

(setq custom-file (locate-user-emacs-file "/home/pedro/.dotfiles/.emacs.d/custom-vars.el"))

To:

(setq custom-file (locate-user-emacs-file "/Users/pedro/.emacs.d/custom-vars.el")) 

Solved the problem on the new macOS machine.

Also, I tweaked the config file to include comments about the problem:

;; Avoid custom variables from Emacs, since this is a handcrafted file
;; Move them to a different file. There is macOS and a nixOS version
;; macOS
(setq custom-file (locate-user-emacs-file "/Users/pedro/.emacs.d/custom-vars.el")) 
;; nixOS config
;;(setq custom-file (locate-user-emacs-file "/home/pedro/.dotfiles/.emacs.d/custom-vars.el"))

(load custom-file 'noerror 'nomessage)