Return syn::Result from extract_doc_line

Update callers to use Iterator::try_fold and propagate errors with ?.
Also switch parse2().ok() to map(Some) and convert early returns to
Ok(...) variants.

Author: rliang

crates/rmcp-macros/src/common.rs

@@ -9,13 +9,16 @@ pub fn none_expr() -> syn::Result<Expr> {
 }
 
 /// Extract documentation from doc attributes
-pub fn extract_doc_line(existing_docs: Option<Expr>, attr: &Attribute) -> Option<Expr> {
+pub fn extract_doc_line(
+    existing_docs: Option<Expr>,
+    attr: &Attribute,
+) -> syn::Result<Option<Expr>> {
     if !attr.path().is_ident("doc") {
-        return None;
+        return Ok(None);
     }
 
     let syn::Meta::NameValue(name_value) = &attr.meta else {
-        return None;
+        return Ok(None);
     };
 
     let value = &name_value.value;
@@ -28,23 +31,23 @@ pub fn extract_doc_line(existing_docs: Option<Expr>, attr: &Attribute) -> Option
         }) => {
             let content = lit_str.value().trim().to_string();
             if content.is_empty() {
-                return existing_docs;
+                return Ok(existing_docs);
             }
             Some(Expr::Lit(syn::ExprLit {
                 attrs: Vec::new(),
                 lit: syn::Lit::Str(syn::LitStr::new(&content, lit_str.span())),
             }))
         }
-        _ => return None,
+        _ => return Ok(None),
     };
 
     match (existing_docs, this_expr) {
         (Some(existing), Some(this)) => {
-            syn::parse2::<Expr>(quote! { concat!(#existing, "\n", #this) }).ok()
+            syn::parse2::<Expr>(quote! { concat!(#existing, "\n", #this) }).map(Some)
         }
-        (Some(existing), None) => Some(existing),
-        (None, Some(this)) => Some(this),
-        _ => None,
+        (Some(existing), None) => Ok(Some(existing)),
+        (None, Some(this)) => Ok(Some(this)),
+        _ => Ok(None),
     }
 }
 

crates/rmcp-macros/src/prompt.rs

@@ -98,15 +98,14 @@ pub fn prompt(attr: TokenStream, input: TokenStream) -> syn::Result<TokenStream>
     };
 
     let name = attribute.name.unwrap_or_else(|| fn_ident.to_string());
-    let description = attribute
-        .description
-        .map(|s| {
-            Expr::Lit(syn::ExprLit {
-                attrs: Vec::new(),
-                lit: syn::Lit::Str(syn::LitStr::new(&s, Span::call_site())),
-            })
-        })
-        .or_else(|| fn_item.attrs.iter().fold(None, extract_doc_line));
+    let description = if let Some(s) = attribute.description {
+        Some(Expr::Lit(syn::ExprLit {
+            attrs: Vec::new(),
+            lit: syn::Lit::Str(syn::LitStr::new(&s, Span::call_site())),
+        }))
+    } else {
+        fn_item.attrs.iter().try_fold(None, extract_doc_line)?
+    };
     let arguments = arguments_expr;
 
     let resolved_prompt_attr = ResolvedPromptAttribute {

crates/rmcp-macros/src/tool.rs

@@ -244,16 +244,14 @@ pub fn tool(attr: TokenStream, input: TokenStream) -> syn::Result<TokenStream> {
         }
     });
 
-    let description_expr = attribute
-        .description
-        .map(|s| {
-            let lit = LitStr::new(&s, Span::call_site());
-            Expr::Lit(syn::ExprLit {
-                attrs: Vec::new(),
-                lit: syn::Lit::Str(lit),
-            })
-        })
-        .or_else(|| fn_item.attrs.iter().fold(None, extract_doc_line));
+    let description_expr = if let Some(s) = attribute.description {
+        Some(Expr::Lit(syn::ExprLit {
+            attrs: Vec::new(),
+            lit: syn::Lit::Str(LitStr::new(&s, Span::call_site())),
+        }))
+    } else {
+        fn_item.attrs.iter().try_fold(None, extract_doc_line)?
+    };
     let resolved_tool_attr = ResolvedToolAttribute {
         name: attribute.name.unwrap_or_else(|| fn_ident.to_string()),
         description: description_expr,