oasis_runtime_sdk_macros/
generators.rs

1use proc_macro2::TokenStream;
2use quote::quote;
3use syn::Ident;
4
5/// Wraps the given code block into an anonymous const code block. Useful when
6/// the code block `use`s stuff that should not leak into the containing scope.
7/// See also https://github.com/serde-rs/serde/issues/159#issuecomment-214002626
8pub fn wrap_in_const(tokens: TokenStream) -> TokenStream {
9    quote! {
10        const _: () = {
11            #tokens
12        };
13    }
14}
15
16/// Determines what crate name should be used to refer to `oasis_runtime_sdk` types.
17/// Required for use within the SDK itself (crates cannot refer to their own names).
18pub fn sdk_crate_path() -> syn::Path {
19    let is_internal = std::env::var("CARGO_PKG_NAME")
20        .map(|pkg_name| pkg_name == "oasis-runtime-sdk")
21        .unwrap_or_default();
22    if is_internal {
23        // Doctests are their own crates, but they share the name of the primary crate.
24        // Thus, the primary crate needs to refer to itself. Either that or depend on unstable
25        // rustdoc env vars.
26        syn::parse_quote!(crate::oasis_runtime_sdk)
27    } else {
28        syn::parse_quote!(::oasis_runtime_sdk)
29    }
30}
31
32pub trait CodedVariant {
33    /// The field in the helper attribute that yields the value provided by `code`.
34    /// For instance, in `#[sdk_event(code = 0)]`, the `FIELD_NAME` would be `code`.
35    const FIELD_NAME: &'static str;
36
37    /// The variant ident.
38    fn ident(&self) -> &Ident;
39
40    /// The code to which the variant should be converted.
41    fn code(&self) -> Option<u32>;
42}
43
44/// Returns a `match` expression that encodes an enum's variants as integral codes.
45pub fn enum_code_converter<V: CodedVariant>(
46    enum_binding: &Ident,
47    variants: &[&V],
48    autonumber: bool,
49) -> TokenStream {
50    if variants.is_empty() {
51        return quote!(0); // Early return with default if there are no variants.
52    }
53
54    let mut next_autonumber = 0u32;
55    let mut reserved_numbers = std::collections::BTreeSet::new();
56    let match_arms = variants.iter().map(|variant| {
57        let variant_ident = variant.ident();
58        let code = match variant.code() {
59            Some(code) => {
60                if reserved_numbers.contains(&code) {
61                    variant_ident
62                        .span()
63                        .unwrap()
64                        .error(format!("code {code} already used"))
65                        .emit();
66                    return quote!({});
67                }
68                reserved_numbers.insert(code);
69                code
70            }
71            None if autonumber => {
72                let mut reserved_successors = reserved_numbers.range(next_autonumber..);
73                while reserved_successors.next() == Some(&next_autonumber) {
74                    next_autonumber += 1;
75                }
76                let code = next_autonumber;
77                reserved_numbers.insert(code);
78                next_autonumber += 1;
79                code
80            }
81            None => {
82                variant_ident
83                    .span()
84                    .unwrap()
85                    .error(format!("missing `{}` for variant", V::FIELD_NAME))
86                    .emit();
87                return quote!();
88            }
89        };
90        quote!(Self::#variant_ident { .. } => { #code })
91    });
92    quote! {
93        match #enum_binding {
94            #(#match_arms)*
95        }
96    }
97}
98
99#[cfg(test)]
100mod tests {
101    use super::*;
102
103    #[test]
104    fn generate_empty_enum_converter() {
105        struct DummyVariant {}
106        impl CodedVariant for DummyVariant {
107            const FIELD_NAME: &'static str = "code";
108            fn ident(&self) -> &Ident {
109                unimplemented!()
110            }
111            fn code(&self) -> Option<u32> {
112                unimplemented!()
113            }
114        }
115        let variants: &[&DummyVariant] = &[];
116
117        let expected: syn::Expr = syn::parse_quote!(0);
118        let converter = enum_code_converter(&quote::format_ident!("the_enum"), variants, false);
119        let actual: syn::Expr = syn::parse2(converter).unwrap();
120        assert_eq!(expected, actual);
121    }
122}
oasis_runtime_sdk_macros/generators.rs

oasis_runtime_sdk_macros/
generators.rs
