1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110

//! Generates builder methods of every field of a struct. It is meant to be used on structs that
//! implement `Default`. There is no separate builder struct generated and no need to call a
//! `build()` method at the end or `.unwrap()`.
//!
//! This crate is used by the crate `leptos-use` for the option structs that
//! can be passed to the various functions.
//!
//! ## Installation
//!
//! In your project folder run
//!
//! ```sh
//! cargo add default-struct-builder
//! ```
//!
//! ## Usage
//!
//! It is very easy to use:
//!
//! ```
//! use default_struct_builder::DefaultBuilder;
//!
//! #[derive(DefaultBuilder, Default)]
//! pub struct SomeOptions {
//!     throttle: f64,
//!
//!     #[builder(into)]
//!     offset: Option<f64>,
//!
//!     #[builder(skip)]
//!     not_included: u32,
//! }
//! ```
//!
//! you can then use the struct like this:
//!
//! ```
//! # use default_struct_builder::DefaultBuilder;
//! #
//! # #[derive(DefaultBuilder, Default)]
//! # pub struct SomeOptions {
//! #     throttle: f64,
//! #
//! #     #[builder(into)]
//! #     offset: Option<f64>,
//! #
//! #     #[builder(skip)]
//! #     not_included: u32,
//! # }
//! #
//! # fn main() {
//! let options = SomeOptions::default().offset(4.0);
//!
//! assert_eq!(options.offset, Some(4.0));
//! assert_eq!(options.throttle, 0.0);
//! assert_eq!(options.not_included, 0);
//! # }
//! ```
//!
//! # How it works
//!
//! The derive macro generates the following code:
//!
//! ```
//! # #[derive(Default)]
//! # pub struct SomeOptions {
//! #     throttle: f64,
//! #     offset: Option<f64>,
//! #     not_included: u32,
//! # }
//! #
//! impl SomeOptions {
//!     pub fn throttle(self, value: f64) -> Self {
//!         Self {
//!             throttle: value,
//!             ..self
//!         }
//!     }
//!
//!     pub fn offset<T>(self, value: T) -> Self
//!     where
//!         T: Into<Option<f64>>,
//!     {
//!         Self {
//!             offset: value.into(),
//!             ..self
//!         }
//!     }
//! }
//! ```
//! ## Related Work
//!
//! For more general purposes please check out the much more powerful
//! [`derive_builder` crate](https://github.com/colin-kiegel/rust-derive-builder).

mod builder;

use builder::DefaultBuilderDeriveInput;
use darling::FromDeriveInput;
use proc_macro::TokenStream;
use quote::quote;
use syn::parse_macro_input;

#[proc_macro_derive(DefaultBuilder, attributes(builder))]
pub fn derive_builder(input: TokenStream) -> TokenStream {
    let input = parse_macro_input!(input as syn::DeriveInput);
    let data = DefaultBuilderDeriveInput::from_derive_input(&input).expect("Wrong options");
    let stream = quote!(#data);
    stream.into()
}