Adds check to ensure config file exists. Fixes: #4513

cmd/cli/app/auth/auth_login.go

@@ -5,6 +5,8 @@ package auth
 
 import (
 	"context"
+	"fmt"
+	"os"
 
 	"github.com/spf13/cobra"
 	"github.com/spf13/viper"
@@ -27,14 +29,24 @@ $XDG_CONFIG_HOME/minder/credentials.json`,
 
 // LoginCommand is the login subcommand
 func LoginCommand(ctx context.Context, cmd *cobra.Command, _ []string, _ *grpc.ClientConn) error {
-	clientConfig, err := config.ReadConfigFromViper[clientconfig.Config](viper.GetViper())
-	if err != nil {
-		return cli.MessageAndError("Unable to read config", err)
-	}
+	v := viper.GetViper()
+
 	// No longer print usage on returned error, since we've parsed our inputs
 	// See https://github.com/spf13/cobra/issues/340#issuecomment-374617413
 	cmd.SilenceUsage = true
 
+	// If config file is specified but doesn't exist, that's an error
+	if configFile := v.GetString("config"); configFile != "" {
+		if _, err := os.Stat(configFile); os.IsNotExist(err) {
+			return cli.MessageAndError("Config file does not exist", fmt.Errorf("file %s not found", configFile))
+		}
+	}
+
+	clientConfig, err := config.ReadConfigFromViper[clientconfig.Config](v)
+	if err != nil {
+		return cli.MessageAndError("Unable to read config", err)
+	}
+
 	filePath, err := cli.LoginAndSaveCreds(ctx, cmd, clientConfig)
 	if err != nil {
 		return cli.MessageAndError("Error ensuring credentials", err)