papito_codegen 0.1.0

Codegen for the Papito WASM Framework
Documentation 
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 quote::Tokens;
use syn::{Item, Type, Ident, Path, ImplItem, ImplItemMethod, FnArg, ArgSelfRef, ArgCaptured,
          ReturnType};
use common::{split_path, component_of_state};

pub fn quote(item: &Item) -> Tokens {
    match *item {
        Item::Impl(ref item_impl) => {
            let self_ty = *item_impl.self_ty.clone();
            let path = component_path_of(self_ty);
            impl_wrapper_for_any_events(item_impl.items.clone(), path)
        }
        _ => {
            panic!("`#[events]` attribute can only be used with an impl block");
        }
    }
}

fn component_path_of(self_ty: Type) -> Path {
    match self_ty {
        Type::Path(type_path) => {
            let (mut path, mut last_segment) = split_path(type_path);
            last_segment.ident = component_of_state(&last_segment.ident);
            path.segments.push(last_segment);
            path
        }
        _ => panic!("Only type paths are allowed for impls attributed with `#[events]`")
    }
}

fn impl_wrapper_for_any_events(items: Vec<ImplItem>, comp_path: Path) -> Tokens {
    let mut iter = items.into_iter();
    let mut event_wrappers = vec![];
    while let Some(ImplItem::Method(method_item)) = iter.next() {
        if has_event_attribute(&method_item) {
            let (fn_name, self_arg, event_arg) = get_metadata(method_item);
            let event_ty = &event_arg.ty;
            let event_ident = Ident::from("ev".to_string());
            if self_arg.mutability.is_some() {
                event_wrappers.push(quote! {
                    fn #fn_name(&self) -> impl FnMut(#event_ty) {
                        let comp = self.inner.clone();
                        move |#event_ident| {
                            comp.borrow_mut().#fn_name(#event_ident);
                        }
                    }
                })
            } else {
                event_wrappers.push(quote! {
                    fn #fn_name(&self) -> impl Fn(#event_ty) {
                        let comp = self.inner.clone();
                        move |#event_ident| {
                            comp.borrow().#fn_name(#event_ident);
                        }
                    }
                })
            }
        }
    }
    quote! {
        impl #comp_path {
            #(#event_wrappers)*
        }
    }
}

fn has_event_attribute(item: &ImplItemMethod) -> bool {
    item.attrs.iter().any(|it| it.path == Path::from(Ident::from("event".to_string())))
}

fn get_metadata(item: ImplItemMethod) -> (Ident, ArgSelfRef, ArgCaptured) {
    let sig = item.sig;
    let fn_name = sig.ident;
    let decl = sig.decl;
    if decl.output != ReturnType::Default {
        panic!("This event method `{}` cannot have a return type", &fn_name)
    }
    let mut args = decl.inputs.into_iter();
    let first_arg = args.next().expect(&format!("This method `{}` has no argument", &fn_name));
    let second_arg = args.next().expect(&format!("This method `{}` does not have second argument", &fn_name));
    if let Some(_) = args.next() {
        panic!("This method `{}` cannot have any more that 2 arguments", &fn_name);
    }
    let first_arg = if let FnArg::SelfRef(self_arg) = first_arg {
        self_arg
    } else {
        panic!("The first arg of `{}` can only be `&self` or `&mut self`", &fn_name);
    };
    let second_arg = if let FnArg::Captured(arg) = second_arg {
        arg
    } else {
        panic!("The second arg of `{}` must be an explicit type", &fn_name);
    };
    (fn_name, first_arg, second_arg)
}