flow_record_derive/
lib.rs

1use darling::FromDeriveInput;
2use proc_macro::TokenStream;
3use quote::quote;
4use record_attributes::RecordAttributes;
5use struct_info::StructInfo;
6use syn::{parse_macro_input, DeriveInput};
7
8mod field_info;
9mod record_attributes;
10mod struct_info;
11mod without_lifetimes;
12
13#[proc_macro_derive(FlowRecord, attributes(flow_record))]
14pub fn derive_flow_record(input: TokenStream) -> TokenStream {
15    let mut input = parse_macro_input!(input as DeriveInput);
16    FromDeriveInput::from_derive_input(&input)
17        .and_then(|attrs| expand(&mut input, attrs))
18        .map(Into::into)
19        // Error handling
20        .unwrap_or_else(|e| e.write_errors().into())
21}
22
23fn expand(ast: &mut syn::DeriveInput, attrs: RecordAttributes) -> darling::Result<TokenStream> {
24    let name = &ast.ident;
25    let name_as_string = name.to_string();
26
27    let descriptor;
28    let child_descriptors;
29    let hash;
30    let values: Vec<_>;
31
32    let from_parameter_name = quote! {self};
33
34    match &ast.data {
35        syn::Data::Struct(s) => {
36            let struct_info = StructInfo::new(name_as_string.clone(), s.clone(), attrs);
37            descriptor = struct_info.descriptor();
38            child_descriptors = struct_info.child_descriptors();
39            hash = struct_info.descriptor_hash();
40            values = struct_info.values(quote! {#from_parameter_name}).collect();
41        }
42
43        syn::Data::Enum(_) => panic!("no support for enums yet"),
44        syn::Data::Union(_) => panic!("no support for unions yet"),
45    }
46
47    let children = child_descriptors.into_iter().map(|c| {
48        let (hash, descriptor) = (c.hash, c.descriptor);
49        quote! {#hash, #descriptor}
50    });
51
52    let (impl_generics, ty_generics, where_clause) = ast.generics.split_for_impl();
53
54    let gen = quote!(
55        use flow_record::prelude::rmpv::Value;
56
57        impl #impl_generics FlowRecord for #name #ty_generics #where_clause {
58            fn name() -> &'static str {
59                #name_as_string
60            }
61            fn descriptor() -> &'static Value {
62                static D: std::sync::LazyLock<Value> = std::sync::LazyLock::new(|| Value::from( #descriptor ) );
63                &*D
64            }
65            fn descriptor_hash() -> u32 {
66                static H: std::sync::LazyLock<u32> = std::sync::LazyLock::new(|| #hash);
67                *H
68            }
69            fn into_value(self) -> Value {
70                Value::Array(vec![
71                    #(#values),*,
72                ])
73            }
74            fn child_descriptors() -> &'static ::std::collections::HashMap<u32, Value> {
75                static D: std::sync::LazyLock<::std::collections::HashMap<u32, Value>> = std::sync::LazyLock::new(||
76                    {
77                        let mut d = ::std::collections::HashMap::new();
78                        #( d.insert( #children ); )*
79                        d
80                    }
81                );
82                &*D
83            }
84        }
85    );
86    Ok(gen.into())
87}
88
89#[proc_macro_attribute]
90pub fn has_descriptor(_input: TokenStream, annotated_item: TokenStream) -> TokenStream {
91    annotated_item
92}
flow_record_derive/lib.rs

flow_record_derive/
lib.rs
