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feat: concat support for mcp_tool macro #23

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Merged
merged 1 commit into from
May 1, 2025
Merged

feat: concat support for mcp_tool macro #23

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126 changes: 83 additions & 43 deletions crates/rust-mcp-macros/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,20 @@ struct McpToolMacroAttributes {
description: Option<String>,
}

use syn::parse::ParseStream;

struct ExprList {
exprs: Punctuated<Expr, Token![,]>,
}

impl Parse for ExprList {
fn parse(input: ParseStream) -> syn::Result<Self> {
Ok(ExprList {
exprs: Punctuated::parse_terminated(input)?,
})
}
}

impl Parse for McpToolMacroAttributes {
/// Parses the macro attributes from a `ParseStream`.
///
Expand All @@ -41,51 +55,77 @@ impl Parse for McpToolMacroAttributes {
for meta in meta_list {
if let Meta::NameValue(meta_name_value) = meta {
let ident = meta_name_value.path.get_ident().unwrap();
if let Expr::Lit(ExprLit {
lit: Lit::Str(lit_str),
..
}) = meta_name_value.value
{
match ident.to_string().as_str() {
"name" => name = Some(lit_str.value()),
"description" => description = Some(lit_str.value()),
_ => {}
let ident_str = ident.to_string();

let value = match &meta_name_value.value {
Expr::Lit(ExprLit {
lit: Lit::Str(lit_str),
..
}) => lit_str.value(),

Expr::Macro(expr_macro) => {
let mac = &expr_macro.mac;
if mac.path.is_ident("concat") {
let args: ExprList = syn::parse2(mac.tokens.clone())?;
let mut result = String::new();

for expr in args.exprs {
if let Expr::Lit(ExprLit {
lit: Lit::Str(lit_str),
..
}) = expr
{
result.push_str(&lit_str.value());
} else {
return Err(Error::new_spanned(
expr,
"Only string literals are allowed inside concat!()",
));
}
}

result
} else {
return Err(Error::new_spanned(
expr_macro,
"Only concat!(...) is supported here",
));
}
}

_ => {
return Err(Error::new_spanned(
&meta_name_value.value,
"Expected a string literal or concat!(...)",
));
}
};

match ident_str.as_str() {
"name" => name = Some(value),
"description" => description = Some(value),
_ => {}
}
}
}
match &name {
Some(tool_name) => {
if tool_name.trim().is_empty() {
return Err(Error::new(
attributes.span(),
"The 'name' attribute should not be an empty string.",
));
}
}
None => {
return Err(Error::new(
attributes.span(),
"The 'name' attribute is required.",
));
}

// Validate presence and non-emptiness
if name.as_ref().map(|s| s.trim().is_empty()).unwrap_or(true) {
return Err(Error::new(
attributes.span(),
"The 'name' attribute is required and must not be empty.",
));
}

match &description {
Some(description) => {
if description.trim().is_empty() {
return Err(Error::new(
attributes.span(),
"The 'description' attribute should not be an empty string.",
));
}
}
None => {
return Err(Error::new(
attributes.span(),
"The 'description' attribute is required.",
));
}
if description
.as_ref()
.map(|s| s.trim().is_empty())
.unwrap_or(true)
{
return Err(Error::new(
attributes.span(),
"The 'description' attribute is required and must not be empty.",
));
}

Ok(Self { name, description })
Expand Down Expand Up @@ -360,7 +400,7 @@ mod tests {
assert!(result.is_err());
assert_eq!(
result.err().unwrap().to_string(),
"The 'name' attribute is required."
"The 'name' attribute is required and must not be empty."
)
}

Expand All @@ -371,7 +411,7 @@ mod tests {
assert!(result.is_err());
assert_eq!(
result.err().unwrap().to_string(),
"The 'description' attribute is required."
"The 'description' attribute is required and must not be empty."
)
}

Expand All @@ -382,7 +422,7 @@ mod tests {
assert!(result.is_err());
assert_eq!(
result.err().unwrap().to_string(),
"The 'name' attribute should not be an empty string."
"The 'name' attribute is required and must not be empty."
);
}
#[test]
Expand All @@ -392,7 +432,7 @@ mod tests {
assert!(result.is_err());
assert_eq!(
result.err().unwrap().to_string(),
"The 'description' attribute should not be an empty string."
"The 'description' attribute is required and must not be empty."
);
}
}