FIX: correctly handle not existing user argument for the set-user function

resolves: Oldes/Rebol-issues#2547

Author: Oldes

src/mezz/mezz-shell.reb

@@ -3,6 +3,7 @@ REBOL [
 	Title: "REBOL 3 Mezzanine: Shell-like Command Functions"
 	Rights: {
 		Copyright 2012 REBOL Technologies
+		Copyright 2012-2023 Rebol Open Source Contributors
 		REBOL is a trademark of REBOL Technologies
 	}
 	License: {
@@ -72,7 +73,11 @@ su: set-user: func[
 	if unset? :name [su/name: none su/data: make map! 1 exit]
 
 	sys/log/info 'REBOL ["Initialize user:" as-green :name]
-	file: to-real-file any [file rejoin [system/options/home #"." :name %.safe]]
+
+	file: any [
+		all [file to-real-file file] ;@@ could to-real-file accept none?
+		rejoin [system/options/home #"." :name %.safe]
+	]
 	sys/log/more 'REBOL ["Checking if exists: " as-green file]
 	unless exists? file [
 		unless n [

src/tests/units/codecs-test.r3

@@ -761,6 +761,7 @@ if find codecs 'safe [
 	;- using environmental variable to avoid interactive password input using `ask`
 	temp: get-env "REBOL_SAFE_PASS"
 	set-env "REBOL_SAFE_PASS" "my-pass"
+	user: system/user ;; store existing user
 	===start-group=== "SAFE codec"		
 		--test-- "Save/Load SAFE file"
 			foreach data [
@@ -772,8 +773,18 @@ if find codecs 'safe [
 				--assert equal? data load save %temp.safe data
 				delete %temp.safe
 			]
+		--test-- "Set-user which does not exists"
+			;@@ https://github.com/Oldes/Rebol-issues/issues/2547
+			--assert not error? try [set-user not-existing-user]
+		--test-- "Initialise new user"
+			--assert not error? try [set-user/n/p temp-user "passw"]
+			--assert system/user/name = @temp-user
+			--assert 'file = exists? try [system/user/data/spec/ref]
+			try [delete system/user/data/spec/ref]
+
 	===end-group===
 	set-env "REBOL_SAFE_PASS" :temp
+	system/user: :user
 ]