PreAction does not trigger on a flag when it is specified by an env variable.

[james-lawrence]

var enabled bool
cmd.Flag("profiler-enable", "enable the profiler").Default("false").
		Envar("PROFILER_ENABLED").PreAction(execute).BoolVar(&enabled)

func execute(c *kingpin.ParseContext) error {
  log.Println("enabling profiler")
  return nil
}

spike --profiler-enable
# enabling profiler

PROFILER_ENABLED=true spike
# nothing output

[alecthomas]

Good catch. I'll try to fix this tonight.

[alecthomas]

Hmm, ok. So this occurs because envars change the default value prior to parsing. I think it would actually require a fair amount of effort to fix, so I might just change the documented behaviour to: Envar(name): Allow the default value to be set via environment variable.. That is not exactly ideal.