(#8) Support opt-out of os.Args

[jeffmccune]

Problem:
Cannot embed machine room as a cobra subcommand because fisk and cobra fight over os.Args

Solution:
Add a CustomArgs and CustomArgsEnabled machine room option to pass args through.

Result:
Machine room can run as a cobra subcommand:

cmd := &cobra.Command{
  Args:               cobra.ArbitraryArgs,
  DisableFlagParsing: true,
  RunE: func(cmd *cobra.Command, args []string) error {
    app, _ := mr.New(mr.Options{
      CustomArgsEnabled: true,
      CustomArgs:        args,
    })
    return app.Run(cmd.Context())
  },
}

Closes: #8

[ripienaar]

nice one, thanks

[jeffmccune]

@ripienaar Thanks for merging this, but I was wondering: Is the boolean unnecessary? Could I have just checked if CustomArgs is nil?

At least this is a bit more readable, so won't change it unless you want me to.

[ripienaar]

Yeah you're right, checking len(CustomArgs)==0 would be better

[jeffmccune]

Cool let me fix it

[ripienaar]

I pushed 2 dependency updates - one also adding a new watcher

https://choria.io/docs/autoagents/watcher_reference/#expression-watcher

[jeffmccune]

Gonna check nil, len and cap are 0 for a nil slice.

package main

import "fmt"

func main() {
	var args []string
	p("args", args)
	fmt.Println()
	p("args2", []string{})
}

func p(name string, args []string) {
	if args == nil {
		fmt.Println(name, "is nil")
	} else {
		fmt.Println(name, "is NOT nil")
	}
	fmt.Printf("%s: %+v\n", name, args)
	fmt.Printf("len(%s): %+v\n", name, len(args))
	fmt.Printf("cap(%s): %+v\n", name, cap(args))
}

❯ go run foo.go
args is nil
args: []
len(args): 0
cap(args): 0

args2 is NOT nil
args2: []
len(args2): 0
cap(args2): 0

[ripienaar]

len()==0 is enough. Nil slice is 0 len.

[jeffmccune]

I left it as a nil check because I think we want to disambiguate between the case where the user passes in args of length 0 and the case where the user didn't pass in any args at all. I think we should only use the override args if they're initialized by the user.