Better Document behavior of DurationSeconds about serde_with

[jonasbb]

Hi, thanks for the suggestion. Do you have a concrete improvement in mind? All the examples with chrono::Duration on the DurationSeconds page use a more explicitly annotated DurationSeconds. The comparison table also lists that chrono::Duration is incompatible with the default format of u64.

use chrono::Duration;

#[serde_as]
#[derive(Deserialize, Serialize)]
struct Durations {
    #[serde_as(as = "DurationSeconds<i64>")]
    d_i64: Duration,
    #[serde_as(as = "DurationSeconds<f64>")]
    d_f64: Duration,
    #[serde_as(as = "DurationSeconds<String>")]
    d_string: Duration,
};

The example under "Advanced serde_as usage" used std::time::Duration. That is not directly obvious, since the import is hidden.

[xiaoas]

imo

• The example on the crate main page should use the explicit annotation, a example for chrono::Duration might be helpful as well.
• The DurationSeconds page should have a example detailing using DurationSeconds<i64> on std::time::Duration, or using DurationSeconds<u64> on chrono::Duration are both incorrect.

What do you think?

[jonasbb]

I made some changes in #576. I unhid the Duration import. I don't like the idea of showing wrong examples. I added some explanatory sentences and added some emphasis to the FORMAT support table for DurationSeconds/TimestampSeconds.