Are OverrideDefaultFromEnvar and Required meant to work together?

[joprice]

From this line of code, it looks like a flag with both OverrideDefaultFromEnvar and Required will cause the parsing to error out, even when an envar is present, since defaultValue is checked on L166 before it is overridden on L172.

kingpin/flags.go

Line 165 in a727460

func (f *FlagClause) init() error {

[alecthomas]

That is incorrect. L166 is merely ensuring that users don't do .Default("value").Required(), as it's essentially a programmer error. Once that check is complete, defaultValue is set from the envar so that (later) execution of the context will pull the default value from the environment.

PS. I added a test to illustrate.