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
|
use proc_macro::TokenStream;
use quote::quote;
use syn::{FnArg, Item, ItemConst, ItemFn, parse_macro_input};
#[proc_macro_attribute]
pub fn export(_attr: TokenStream, item: TokenStream) -> TokenStream {
match parse_macro_input!(item as Item) {
Item::Fn(function) => export_fn(function),
Item::Const(constant) => export_const(constant),
other => syn::Error::new_spanned(other, "#[export] only supports fn and const items")
.to_compile_error()
.into(),
}
}
fn export_fn(function: ItemFn) -> TokenStream {
let param_count = function
.sig
.inputs
.iter()
.filter(|arg| matches!(arg, FnArg::Typed(_)))
.count();
if param_count > 1 {
return syn::Error::new_spanned(
&function.sig.inputs,
"#[export] functions must accept a single options struct, not positional arguments. \
Wrap parameters in a struct: `fn foo(FooOptions { a, b }: FooOptions)`",
)
.to_compile_error()
.into();
}
let js_name = snake_to_camel(&function.sig.ident.to_string());
quote! {
#[cfg_attr(feature = "wasm", ::wasm_bindgen::prelude::wasm_bindgen(js_name = #js_name))]
#function
}
.into()
}
fn export_const(constant: ItemConst) -> TokenStream {
let js_name = constant.ident.to_string();
let const_ident = &constant.ident;
let getter_ident = syn::Ident::new(
&format!("__const_{}", constant.ident.to_string().to_lowercase()),
constant.ident.span(),
);
quote! {
#constant
#[cfg(feature = "wasm")]
#[::wasm_bindgen::prelude::wasm_bindgen(js_name = #js_name)]
pub fn #getter_ident() -> f64 {
#const_ident as f64
}
}
.into()
}
fn snake_to_camel(name: &str) -> String {
let mut camel = String::with_capacity(name.len());
let mut should_uppercase_next = false;
for character in name.chars() {
if character == '_' {
should_uppercase_next = true;
continue;
}
if should_uppercase_next {
camel.push(character.to_ascii_uppercase());
should_uppercase_next = false;
continue;
}
camel.push(character);
}
camel
}
#[cfg(test)]
mod tests {
use super::snake_to_camel;
#[test]
fn converts_snake_case_to_camel_case() {
assert_eq!(snake_to_camel("do_something"), "doSomething");
assert_eq!(snake_to_camel("a_b_c"), "aBC");
assert_eq!(snake_to_camel("already"), "already");
}
}
|
