How to use sources from config file that was set via flag?

[dearchap]

Discussed in #2032

^{Originally posted by plandem December 23, 2024}
Hi

Sadly, I cant find how to implement this simple setup:

sources := cli.NewValueSourceChain()
app := &cli.Command{
		EnableShellCompletion:  true,
		UseShortOptionHandling: true,
		Before: func(ctx context.Context, cmd *cli.Command) (context.Context, error) {
			config := cmd.String("config")
			if len(config) > 0 {
				configFile := fmt.Sprintf("%s.yaml", cmd.String("config"))
				if _, err := os.Stat(configFile); os.IsNotExist(err) {
					return ctx, fmt.Errorf("could not load config file: %s", configFile)
				}

				sources.Append(cli.Files(configFile))
				return ctx, nil
			}

			return ctx, nil
		},
		OnUsageError: func(ctx context.Context, cmd *cli.Command, err error, isSubcommand bool) error {
			os.Exit(1)
			return err
		},
		ShellComplete: func(ctx context.Context, cmd *cli.Command) {
			fmt.Fprintf(cmd.Root().Writer, "check\nnotify\nvalidate\n")
		},
		Flags: []cli.Flag{
			&cli.StringFlag{
				Name:    "config",
				Aliases: []string{"c"},
				Usage:   "Load configuration from `FILE`",
			},
		},
		Commands: []*cli.Command{
			{
				Name:   "notify",
				Usage:  "Notify Telegram about updates",
				Flags:  []cli.Flag{
					&cli.StringFlag{
						Name:     "token",
						Required: true,
						Usage:    "`TOKEN` of Telegram's bot",
						//Sources:  altsrc.YAML("notify.telegram-chat", ???), // how to use sources/files from 'Before'?
					},
					&cli.StringFlag{
						Name:     "chat",
						Required: true,
						Usage:    "`ID` of Telegram's chat to send updates",
						//Sources:  altsrc.YAML("notify.telegram-chat", ???),  // how to use sources/files from 'Before'?
					},
				}
				Action: notify.Telegram,
			},

Setup is quite typical, tbh - provide custom config file and use values from it. But from docs, it looks like it may work only with hardcoded names? Any direction? Ofc, I could hack around to get config's file outside from the cli package, but I feel that could miss something and there is a built-in way to achieve it.

Can anybody point me to what direction should I look?

P.S.: v3 of cli

[dearchap]

@plandem I have a PoC PR which might help resolve your issue. You may have to customize the value source to read the flag value and load files. I have to think more on this.

[plandem]

@plandem I have a PoC PR which might help resolve your issue. You may have to customize the value source to read the flag value and load files. I have to think more on this.

not sure how to use it :( since its PoC, do you need some feedback or what is the next step to make it possible (i mean original topic of discussion)?