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//! Completion Attribute Macro Implementation
//!
//! This module provides the `#[completion]` attribute macro for automatically
//! generating structs that implement the `Completion` trait from functions.
use proc_macro::TokenStream;
use quote::quote;
use syn::{Ident, ItemFn, parse_macro_input};
#[cfg(feature = "comp")]
pub fn completion_attr(attr: TokenStream, item: TokenStream) -> TokenStream {
// Parse the attribute arguments (e.g., HelloEntry from #[completion(HelloEntry)])
let previous_type_ident = if attr.is_empty() {
return syn::Error::new(
proc_macro2::Span::call_site(),
"completion attribute requires a previous type argument, e.g. #[completion(HelloEntry)]",
)
.to_compile_error()
.into();
} else {
parse_macro_input!(attr as Ident)
};
// Parse the function item
let input_fn = parse_macro_input!(item as ItemFn);
// Validate the function is not async
if input_fn.sig.asyncness.is_some() {
use syn::spanned::Spanned;
return syn::Error::new(input_fn.sig.span(), "Completion function cannot be async")
.to_compile_error()
.into();
}
// Get the function signature parts
let sig = &input_fn.sig;
let inputs = &sig.inputs;
let output = &sig.output;
// Check that the function has exactly one parameter
if inputs.len() != 1 {
use syn::spanned::Spanned;
return syn::Error::new(
inputs.span(),
"Completion function must have exactly one parameter",
)
.to_compile_error()
.into();
}
// Get the function body
let fn_body = &input_fn.block;
// Get function attributes (excluding the completion attribute)
let mut fn_attrs = input_fn.attrs.clone();
fn_attrs.retain(|attr| !attr.path().is_ident("completion"));
// Get function visibility
let vis = &input_fn.vis;
// Get function name
let fn_name = &sig.ident;
// Generate struct name from function name using pascal_case
let pascal_case_name = just_fmt::pascal_case!(fn_name.to_string());
let struct_name = Ident::new(&pascal_case_name, fn_name.span());
// Generate the struct and implementation
let expanded = quote! {
#(#fn_attrs)*
#vis struct #struct_name;
impl ::mingling::Completion for #struct_name {
type Previous = #previous_type_ident;
fn comp(#inputs) #output {
#fn_body
}
}
// Keep the original function for internal use
#(#fn_attrs)*
#vis fn #fn_name(#inputs) #output {
#fn_body
}
};
let completion_entry = quote! {
Self::#previous_type_ident => <#struct_name as ::mingling::Completion>::comp(ctx),
};
let mut completions = crate::COMPLETIONS.lock().unwrap();
let completion_str = completion_entry.to_string();
completions.insert(completion_str);
expanded.into()
}
|
