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use crate::SynResult;
use crate::TokenStream2;
use crate::config::default_feature_name;
use proc_macro::TokenStream;
use quote::quote;
use syn::{
LitStr, Token,
parse::{Parse, ParseStream},
parse_macro_input,
};
#[doc = include_str!("../doc/args/invoke.md")]
pub enum InvokeArgs {
/// invoke!(expr) — feature name defaults to "async"
Default(TokenStream2),
/// invoke!("feat" => expr) — explicit feature name
Explicit(LitStr, TokenStream2),
}
impl Parse for InvokeArgs {
fn parse(input: ParseStream) -> SynResult<Self> {
if input.peek(LitStr) {
let feat: LitStr = input.parse()?;
input.parse::<Token![=>]>()?;
let expr: TokenStream2 = input.parse()?;
Ok(InvokeArgs::Explicit(feat, expr))
} else {
let expr: TokenStream2 = input.parse()?;
Ok(InvokeArgs::Default(expr))
}
}
}
pub(crate) fn invoke(input: TokenStream) -> TokenStream {
let input = parse_macro_input!(input as InvokeArgs);
let expanded = match input {
InvokeArgs::Default(expr) => {
let feat = default_feature_name();
quote! {{
#[cfg(feature = #feat)]
{ #expr.await }
#[cfg(not(feature = #feat))]
{ #expr }
}}
}
InvokeArgs::Explicit(feat, expr) => {
let feat_name = &feat;
quote! {{
#[cfg(feature = #feat_name)]
{ #expr.await }
#[cfg(not(feature = #feat_name))]
{ #expr }
}}
}
};
TokenStream::from(expanded)
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn default_variant() {
// Input: an expression without feature name → Default variant
let input: proc_macro2::TokenStream = "compute(5)".parse().unwrap();
let args: InvokeArgs = syn::parse2(input).unwrap();
match args {
InvokeArgs::Default(_) => {} // expected
_ => panic!("expected Default variant"),
}
}
#[test]
fn explicit_variant() {
// Input: "my_ft" => expr → Explicit variant with feature "my_ft"
let input: proc_macro2::TokenStream = "\"my_ft\" => compute(5)".parse().unwrap();
let args: InvokeArgs = syn::parse2(input).unwrap();
match args {
InvokeArgs::Explicit(feat, _) => {
assert_eq!(feat.value(), "my_ft");
}
_ => panic!("expected Explicit variant"),
}
}
}
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