When time::serde::format_description defined submodule::option returns None?

[Neutroni]

I am trying to parse some timestamps that might not be present and trying to use #[serde(with = "my_format::option")] to indicate that the value might not be present but it seems that Option<Date> behaves differently than at least Option<String> when de-serializing, this might not necessarily be a bug but I want to know under what conditions the de-serialized Option<Date> can be None.
Following is my code that I expected to run but panics because the field is missing.

use time::PrimitiveDateTime;
use serde::{Deserialize, Serialize};

// Makes a module `mod my_format { ... }`.
time::serde::format_description!(my_format, PrimitiveDateTime, "[year]-[month]-[day] [hour]:[minute]:[second].[subsecond]");

#[derive(Serialize, Deserialize, Debug)]
struct SerializesWithCustom {
    #[serde(with = "my_format")]
    dt: PrimitiveDateTime,
    #[serde(with = "my_format::option")]
    maybe_dt: Option<PrimitiveDateTime>,
}

fn main() {
    let data = r#"
        {
            "dt": "2022-01-01 12:00:00.0"
        }"#;

    // Parse the string of data into serde_json::Value.
    let v: SerializesWithCustom = serde_json::from_str(data)
        .expect("Failed to parse input");
    println!("{:?}", v);
}

Chancing the Option<PrimitiveDateTime> to Option<String> and removing the #[serde(with = "my_format::option")] causes
the code to behave as I would expect.

Dependencies:

serde = { version = "1.0.136", features = ["derive"] }
serde_json = "1.0.79"
time = { version = "0.3.9", features = ["macros", "serde-human-readable", "serde"] }

In case anyone finds this and wonders how to fix the issue add the attribute default to the field, keeping the question open since the behaviour without the attribute is unexpected, might be documentation issue assuming not a bug.

[jhpratt]

Deserializing Option<Date> will be None if the value is null (in JSON — other formats have their own equivalents). When this was brought up before, I was unable to find a way to fall back to None if the value is not present. You'd have to use #[serde(default)] on the field as well. The name may be different, as I'm typing this from memory.

[Neutroni]

Thank you, Originally I was working with TOML which as far as I know does not have null. It is possible that
https://docs.rs/time/0.3.9/time/serde/macro.format_description.html
needs to be updated to document this behaviour. Maybe something like:
The returned Option will contain de-serialized value if present, None if field is present and contains a "null" value, to de-serialize missing fields as None add #[serde(default)] annotation.