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|
use proc_macro::TokenStream;
use quote::quote;
use syn::{ItemFn, parse_macro_input};
/// A procedural macro for generating structs that implement the Action trait
///
/// Usage:
/// #[action_gen] or #[action_gen(local)]
/// pub fn my_action(ctx: ActionContext, arg: MyArg) -> Result<MyReturn, TcpTargetError> {
/// todo!()
/// }
#[proc_macro_attribute]
pub fn action_gen(attr: TokenStream, item: TokenStream) -> TokenStream {
let input_fn = parse_macro_input!(item as ItemFn);
let is_local = if attr.is_empty() {
false
} else {
let attr_str = attr.to_string();
attr_str == "local" || attr_str.contains("local")
};
generate_action_struct(input_fn, is_local).into()
}
fn generate_action_struct(input_fn: ItemFn, _is_local: bool) -> proc_macro2::TokenStream {
let fn_vis = &input_fn.vis;
let fn_sig = &input_fn.sig;
let fn_name = &fn_sig.ident;
let fn_block = &input_fn.block;
validate_function_signature(fn_sig);
let (arg_type, return_type) = extract_types(fn_sig);
let struct_name = quote::format_ident!("{}", convert_to_pascal_case(&fn_name.to_string()));
let action_name_ident = &fn_name;
quote! {
#[derive(Debug, Clone, Default)]
#fn_vis struct #struct_name;
impl vcs_service::action::Action<#arg_type, #return_type> for #struct_name {
fn action_name() -> &'static str {
Box::leak(string_proc::snake_case!(stringify!(#action_name_ident)).into_boxed_str())
}
fn is_remote_action() -> bool {
!#_is_local
}
async fn process(context: vcs_service::action::ActionContext, args: #arg_type) -> Result<#return_type, tcp_connection::error::TcpTargetError> {
#fn_block
}
}
#[deprecated = "This function is used by #[action_gen] as a template."]
#[doc = " This function is used by #[action_gen] as a template to generate the struct. "]
#[doc = " It is forbidden to call it anywhere."]
#[doc = " You should use the generated struct to register this function in `ActionPool`"]
#[doc = " and call it using the function name."]
#fn_vis #fn_sig #fn_block
}
}
fn validate_function_signature(fn_sig: &syn::Signature) {
if !fn_sig.asyncness.is_some() {
panic!("Expected async function for Action, but found synchronous function");
}
if fn_sig.inputs.len() != 2 {
panic!(
"Expected exactly 2 arguments for Action function: ctx: ActionContext and arg: T, but found {} arguments",
fn_sig.inputs.len()
);
}
let return_type = match &fn_sig.output {
syn::ReturnType::Type(_, ty) => ty,
_ => panic!(
"Expected Action function to return Result<T, TcpTargetError>, but found no return type"
),
};
if let syn::Type::Path(type_path) = return_type.as_ref() {
if let Some(segment) = type_path.path.segments.last() {
if segment.ident != "Result" {
panic!(
"Expected Action function to return Result<T, TcpTargetError>, but found different return type"
);
}
}
} else {
panic!(
"Expected Action function to return Result<T, TcpTargetError>, but found no return type"
);
}
}
fn convert_to_pascal_case(s: &str) -> String {
s.split('_')
.map(|word| {
let mut chars = word.chars();
match chars.next() {
None => String::new(),
Some(first) => first.to_uppercase().collect::<String>() + chars.as_str(),
}
})
.collect()
}
fn extract_types(fn_sig: &syn::Signature) -> (proc_macro2::TokenStream, proc_macro2::TokenStream) {
let mut inputs = fn_sig.inputs.iter();
let _ = inputs.next();
let arg_type = match inputs.next() {
Some(syn::FnArg::Typed(pat_type)) => {
let ty = &pat_type.ty;
quote::quote!(#ty)
}
_ => {
panic!("Expected the second argument to be a typed parameter, but found something else")
}
};
let return_type = match &fn_sig.output {
syn::ReturnType::Type(_, ty) => {
if let syn::Type::Path(type_path) = ty.as_ref() {
if let syn::PathArguments::AngleBracketed(args) =
&type_path.path.segments.last().unwrap().arguments
{
if let Some(syn::GenericArgument::Type(ty)) = args.args.first() {
quote::quote!(#ty)
} else {
panic!("Expected to extract the success type of Result, but failed");
}
} else {
panic!("Expected Result type to have generic parameters, but found none");
}
} else {
panic!("Expected return type to be Result, but found different type");
}
}
_ => panic!("Expected function to have return type, but found none"),
};
(arg_type, return_type)
}
|
