utility types

This crate use proc-macro to realize several utility types of Typescript in Rust.

macro	Typescript Utility Type
[Partial]	Partial<Type>
[Required]	Required<Type>
[Pick]	Pick<Type, Keys>
[Omit]	Omit<Type, Keys>
[Extract]	Extract<Type, Union>
[Exclude]	Exclude<UnionType, ExcludedMembers>

Example

Here is an example of how to use this crate.

use utility_types::{Omit, Partial, Pick, Required};
#[derive(Clone, Partial, Required, Pick, Omit)]
#[partial(ident = PartialFoo, derive(Debug, PartialEq), forward_attrs())]
#[required(ident = RequiredFoo, derive(Debug, PartialEq), forward_attrs())]
#[pick(arg(ident = PickAB, fields(a, b), derive(Debug, PartialEq)), forward_attrs())]
#[omit(arg(ident = OmitCD, fields(c, d), derive(Debug, PartialEq)), forward_attrs())]
pub struct Foo {
    a: u8,
    b: Option<u8>,
    c: Option<Vec<u8>>,
}

The above code will generate the following code.

#[derive(Debug, PartialEq)]
pub struct PartialFoo {
    a: Option<u8>,
    b: Option<Option<u8>>,
    c: Option<Option<Vec<u8>>>,
}
#[derive(Debug, PartialEq)]
pub struct RequiredFoo {
    a: u8,
    b: u8,
    c: Vec<u8>,
}
#[derive(Debug, PartialEq)]
pub struct PickAB {
    a: u8,
    b: Option<u8>,
}
#[derive(Debug, PartialEq)]
pub struct OmitCD {
    a: u8,
    b: Option<u8>,
}

Some useful traits are also generated:

• From<Foo> for PartialFoo, PickAB, OmitCD
• From<PartialFoo> for Foo

Forwarding Attributes

To use this crate with other crates that need attributes, you can use the forward_attrs attribute to control which attributes are forwarded to the generated struct or enum.

use serde::{Deserialize, Serialize};
use utility_types::Omit;

#[derive(Debug, PartialEq, Serialize, Deserialize, Omit)]
#[omit(
    arg(
        ident = OmitCD,
        fields(c, d),
        derive(Debug, PartialEq, Serialize, Deserialize),
        forward_attrs(serde)
    )
)]
#[serde(rename_all = "UPPERCASE")]
pub struct Foo {
    a: u8,
    b: Option<u8>,
    c: Option<Vec<u8>>,
}

let omit_cd: OmitCD = serde_json::from_str(r#"{"A": 1, "B": 2}"#).unwrap();
assert_eq!(omit_cd, OmitCD { a: 1, b: Some(2) });

The behavior of the forward_attrs attribute is as follows:

• If not provided, all attributes are forwarded by default.
• If provided with a list of attributes, only the specified attributes are forwarded.
  • For example, forward_attrs(doc, serde) will forward only doc and serde.
  • If provided with only * (forward_attrs(*)), all attributes are forwarded.
  • If provided with an empty list (forward_attrs()), no attributes are forwarded.
• If provided with a list inside not(), all attributes except the specified attributes are forwarded.
  • For example, forward_attrs(not(serde)) will forward all attributes except serde.

Known Issue

Currently I don't analyze which generic is used in the generated struct or enum. So rustc will complain if the field with generic is not included in the generated struct or enum.