feat: add `get_default_empty_record`

[lucatrv]

Summary by CodeRabbit

• New Features
  • Introduced a function to retrieve default deserialized records for structs, enhancing customization of default record definitions.

[coderabbitai[bot]]

Walkthrough

This update introduces a new function get_default_serde_record to the library, enhancing the serde::Deserialize trait implementation. It's designed to simplify the process of defining default records for structs, particularly useful when working with custom default definitions. The addition is complemented by test cases to ensure its functionality and reliability, marking a significant improvement in the library's usability for developers dealing with serialization and deserialization.

Changes

File(s)	Change Summary
src/serde_introspection.rs	Added get_default_serde_record function and test cases for enhanced usability.

🐇✨ In the land of code and byte,
A rabbit hopped into the light.
With a flick and a hop, a new function's born,
To ease the devs' toil from dusk till morn.
"Fear not," it squeaked, with a twinkle in its eye,
"For I bring ease to serialize, no longer shall you sigh."
🌟📜

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[iddm]

@coderabbitai review

[iddm]

Hi @lucatrv ! First and foremost, thank you for your contribution!

Can you please provide a use case for this function to be useful? I am not sure I understand why, for example, and when, I would use it. For example, the code you provided:

#[derive(serde::Deserialize, PartialEq, Debug)]
struct Record {
    #[serde(default = "default_string")]
    label: String,
    #[serde(default = "default_f64")]
    value: f64,
}

fn default_string() -> String {
    String::from("default")
}

fn default_f64() -> f64 {
    1.0
}

let empty_record = get_default_empty_record::<Record>().unwrap();
assert_eq!(
    empty_record,
    Record {
        label: String::from("default"),
        value: 1.0
    }
);

How is it different from this, without using serde at all?

#[derive(serde::Deserialize, PartialEq, Debug)]
struct Record {
    label: String,
    value: f64,
}

impl Default for Record {
    fn default() -> Self {
        Self {
            label: default_string(),
            value: default_f64(),
        }
    }
}

fn default_string() -> String {
    String::from("default")
}

fn default_f64() -> f64 {
    1.0
}

let empty_record = Record::default();
assert_eq!(
    empty_record,
    Record {
        label: String::from("default"),
        value: 1.0
    }
);

[lucatrv]

@iddm I agree that the example above is trivial and can easily be implemented as you showed, however it was intended just to show how the get_default_empty_record method works, not to show a useful use case.

Please consider however that often we deal with long deserialize structs having most fields implementing the Default trait, while maybe one or two use custom types which do not implement it (for instance Result<f64, String>). Of course it is always possible to deal also with these cases as you showed, but it is much simpler and cleaner to rely on Serde's #[serde(default = "path")] field attribute.

In general, any time the #[serde(default = "path")] field attribute is used, it is much easier and safe to use the get_default_empty_record instead of implementing the Default trait separately, paying attention to follow exactly what was specified through Serde's field attributes, which may easily lead to bugs as well.

From another point of view, IMHO what you wrote could also be applied to most helping functions. For instance we could certainly live for instance also without the deserialize_bool_from_anything, as we can implement it in our code as needed, but I think they are all useful helping functions which shorten and simplifies our code.

[lucatrv]

I added some more explanation in the docstring and example.

[iddm]

@iddm I agree that the example above is trivial and can easily be implemented as you showed, however it was intended just to show how the get_default_empty_record method works, not to show a useful use case.

Please consider however that often we deal with long deserialize structs having most fields implementing the Default trait, while maybe one or two use custom types which do not implement it (for instance Result<f64, String>). Of course it is always possible to deal also with these cases as you showed, but it is much simpler and cleaner to rely on Serde's #[serde(default = "path")] field attribute.

In general, any time the #[serde(default = "path")] field attribute is used, it is much easier and safe to use the get_default_empty_record instead of implementing the Default trait separately, paying attention to follow exactly what was specified through Serde's field attributes, which may easily lead to bugs as well.

From another point of view, IMHO what you wrote could also be applied to most helping functions. For instance we could certainly live for instance also without the deserialize_bool_from_anything, as we can implement it in our code as needed, but I think they are all useful helping functions which shorten and simplifies our code.

I see. Thank you for the explanation.

What do you think about renaming the function to get_default_serde_record? To show that it will use the #[serde(default)]. Also, do you mind if we add a clearer text explanation in the document to explain the difference between this function and using the Default trait, the same way you explained it to me? Would it make sense?

[lucatrv]

What do you think about renaming the function to get_default_serde_record? To show that it will use the #[serde(default)]. Also, do you mind if we add a clearer text explanation in the document to explain the difference between this function and using the Default trait, the same way you explained it to me? Would it make sense?

I did as suggested, see if you like it now otherwise please feel free to elaborate further as you will.

[iddm]

Thank you for the contribution and taking time to implement this!

[iddm]

https://crates.io/crates/serde-aux/4.5.0