[v3] `Validator` seems to always receive the empty string

[zx8]

Info:

• Using v3.0.0-alpha7

Code

package main

import (
  "context"
  "fmt"
  "log"
  "os"
  "slices"

  "github.com/urfave/cli/v3"
)

func main() {
  cmd := &cli.Command{
    Name: "example",
    Flags: []cli.Flag{
      &cli.StringFlag{
        Name: "foo",
        Validator: func(s string) error {
          allowed := []string{"a", "b", "c"}
          if slices.Contains(allowed, s) {
            return nil
          }
          return fmt.Errorf("foo must be one of %s, not [%s]", allowed, s)
        },
      },
    },
  }

  if err := cmd.Run(context.Background(), os.Args); err != nil {
    log.Fatal(err)
  }
}

Expected

$ go run . --foo=a
<no error>

Actual

$ go run . --foo=a
foo must be one of [a b c], not []

[dearchap]

@zx8 I see the issue. It is trying to validate the "default" value which in your case is "" since nothing is set. Can you set StringFlag.Value to "a"(say) and see what happens ?

[zx8]

@dearchap You are correct. It seems to be validating the default rather than the supplied value.

[dearchap]

No it valids default value and if that succeeds then does the supplied value.

[zx8]

Aha, ok. I'll add the default to the validator then! Thanks.