internal/sys: separate hsu uid cache

This begins the effort of the removal of the sys package.

Signed-off-by: Ophestra <cat@gensokyo.uk>

cmd/hakurei/command.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"io"
 	"log"
@@ -20,6 +21,7 @@ import (
 	"hakurei.app/internal/app"
 	"hakurei.app/internal/app/state"
 	"hakurei.app/internal/hlog"
+	"hakurei.app/internal/sys"
 	"hakurei.app/system"
 	"hakurei.app/system/dbus"
 )
@@ -272,20 +274,19 @@ func runApp(config *hst.Config) {
 // fatal prints the error message according to [container.GetErrorMessage], or fallback
 // prepended to err if an error message is not available, followed by a call to [os.Exit](1).
 func fatal(fallback string, err error) {
-	m, ok := container.GetErrorMessage(err)
-	if !ok {
-		log.Fatal(fallback, err)
-		return
-	}
-
 	// this indicates the error message has already reached stderr, outside the current process's control;
-	// this is only reached when hsu fails for any reason, as we do not want a second error message following hsu
-	// TODO(ophestra): handle the hsu error here instead of relying on a magic string
-	if m == "\x00" {
+	// this is only reached when hsu fails for any reason, as a second error message following hsu is confusing
+	if errors.Is(err, sys.ErrHsuAccess) {
 		hlog.Verbose("*"+fallback, err)
 		os.Exit(1)
 		return
 	}
 
+	m, ok := container.GetErrorMessage(err)
+	if !ok {
+		log.Fatalln(fallback, err)
+		return
+	}
+
 	log.Fatal(m)
 }