No time.Duration#UnmarshalText; is there a good reason?

[Corin Lawson]

It seems obvious (to me) that the encoding.TextUnmarshaler interface could be implemented for time.Duration (it is implemented for time.Time, afterall).

The fact that it is not gives me pause... is there a good reason that the stdlib has not done this?  What issues am I facing if I do this: https://go.dev/play/p/nHBfS7TJQtJ

```

// UnmarshalText implements the encoding.TextUnmarshaler interface.
func (d *Duration) UnmarshalText(data []byte) error {
        val, err := time.ParseDuration(string(data))
        *d = Duration(val)
        return err
}

```

Cheers,

Corin.

[Ian Lance Taylor]

A time.Duration is just an integer. The standard text marshaling and
unmarshaling work fine.

Ian

[Corin Lawson]

> The standard text marshaling and unmarshaling work fine.

Ok, I get you.

I guess I'm looking for something a little more human friendly than nanoseconds!

In that case I'll proceed with my new-type, thanks!

[roger peppe]

They do work fine in the technical sense, but marshalling a 1s duration as 1000000000 doesn't make for a particularly readable specification of a duration when found in configuration (it's so easy to misread the number of digits). I've often wrapped a time.Duration in a type that implements marshaling and unmarshaling so it's possible to write 1s, 500ms, etc.

 

Unfortunately I don't believe that's possible to add retrospectively because marshaling using Duration.String would break any existing users that expect a number.

  cheers,

    rog.

Ian

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[Tamás Gulácsi]

time.Duration.String() already does the pretty printing: https://pkg.go.dev/time@master#Duration.String
time.ParseDuration is the parser which could be used in UnmarshalText.