ragmcp/tools/parse_rust_ast.rs

// Build from project root:
// rustc -O -o tools/parse_rust_ast tools/parse_rust_ast.rs

use std::env;
use std::fs;
use std::process;
use syn::{FnArg, Item, ItemEnum, ItemFn, ItemImpl, ItemStruct, ItemTrait, Pat, Type, Visibility};

#[derive(serde::Serialize)]
struct RustDecl {
    name: String,
    type_: String,
    start_line: usize,
    end_line: usize,
    visibility: String,
    is_async: bool,
    is_unsafe: bool,
    generics: Vec<String>,
    traits: Vec<String>,
    fields: Vec<String>,
    methods: Vec<String>,
    return_type: Option<String>,
    parameters: Vec<String>,
}

fn main() {
    let args: Vec<String> = env::args().collect();
    if args.len() < 2 {
        eprintln!("Usage: {} <file.rs>", args[0]);
        process::exit(1);
    }

    let filename = &args[1];
    let content = match fs::read_to_string(filename) {
        Ok(content) => content,
        Err(e) => {
            eprintln!("ERR: Failed to read file {}: {}", filename, e);
            process::exit(2);
        }
    };

    let syntax = match syn::parse_file(&content) {
        Ok(syntax) => syntax,
        Err(e) => {
            eprintln!("ERR: Failed to parse Rust file {}: {}", filename, e);
            process::exit(3);
        }
    };

    let mut decls = Vec::new();

    for item in syntax.items {
        match item {
            Item::Fn(item_fn) => {
                if let Some(decl) = parse_function(item_fn, &content) {
                    decls.push(decl);
                }
            }
            Item::Struct(item_struct) => {
                if let Some(decl) = parse_struct(item_struct, &content) {
                    decls.push(decl);
                }
            }
            Item::Enum(item_enum) => {
                if let Some(decl) = parse_enum(item_enum, &content) {
                    decls.push(decl);
                }
            }
            Item::Trait(item_trait) => {
                if let Some(decl) = parse_trait(item_trait, &content) {
                    decls.push(decl);
                }
            }
            Item::Impl(item_impl) => {
                if let Some(decl) = parse_impl(item_impl, &content) {
                    decls.push(decl);
                }
            }
            Item::Mod(item_mod) => {
                if let Some(decl) = parse_mod(item_mod, &content) {
                    decls.push(decl);
                }
            }
            _ => {}
        }
    }

    let output = serde_json::to_string(&decls).unwrap();
    println!("{}", output);
}

fn parse_function(item_fn: ItemFn, content: &str) -> Option<RustDecl> {
    let start_line = item_fn.span().start().line;
    let end_line = item_fn.span().end().line;

    let mut parameters = Vec::new();
    for input in &item_fn.sig.inputs {
        if let FnArg::Typed(pat_type) = input {
            if let Pat::Ident(pat_ident) = &*pat_type.pat {
                parameters.push(pat_ident.ident.to_string());
            }
        }
    }

    let return_type = match &item_fn.sig.output {
        syn::ReturnType::Default => None,
        syn::ReturnType::Type(_, ty) => Some(type_to_string(ty)),
    };

    Some(RustDecl {
        name: item_fn.sig.ident.to_string(),
        type_: "function".to_string(),
        start_line,
        end_line,
        visibility: visibility_to_string(&item_fn.vis),
        is_async: item_fn.sig.asyncness.is_some(),
        is_unsafe: item_fn.sig.unsafety.is_some(),
        generics: item_fn
            .sig
            .generics
            .params
            .iter()
            .map(|param| param.to_string())
            .collect(),
        traits: Vec::new(),
        fields: Vec::new(),
        methods: Vec::new(),
        return_type,
        parameters,
    })
}

fn parse_struct(item_struct: ItemStruct, content: &str) -> Option<RustDecl> {
    let start_line = item_struct.span().start().line;
    let end_line = item_struct.span().end().line;

    let fields: Vec<String> = item_struct
        .fields
        .iter()
        .filter_map(|field| field.ident.as_ref().map(|ident| ident.to_string()))
        .collect();

    Some(RustDecl {
        name: item_struct.ident.to_string(),
        type_: "struct".to_string(),
        start_line,
        end_line,
        visibility: visibility_to_string(&item_struct.vis),
        is_async: false,
        is_unsafe: false,
        generics: item_struct
            .generics
            .params
            .iter()
            .map(|param| param.to_string())
            .collect(),
        traits: Vec::new(),
        fields,
        methods: Vec::new(),
        return_type: None,
        parameters: Vec::new(),
    })
}

fn parse_enum(item_enum: ItemEnum, content: &str) -> Option<RustDecl> {
    let start_line = item_enum.span().start().line;
    let end_line = item_enum.span().end().line;

    let variants: Vec<String> = item_enum
        .variants
        .iter()
        .map(|variant| variant.ident.to_string())
        .collect();

    Some(RustDecl {
        name: item_enum.ident.to_string(),
        type_: "enum".to_string(),
        start_line,
        end_line,
        visibility: visibility_to_string(&item_enum.vis),
        is_async: false,
        is_unsafe: false,
        generics: item_enum
            .generics
            .params
            .iter()
            .map(|param| param.to_string())
            .collect(),
        traits: Vec::new(),
        fields: variants,
        methods: Vec::new(),
        return_type: None,
        parameters: Vec::new(),
    })
}

fn parse_trait(item_trait: ItemTrait, content: &str) -> Option<RustDecl> {
    let start_line = item_trait.span().start().line;
    let end_line = item_trait.span().end().line;

    let methods: Vec<String> = item_trait
        .items
        .iter()
        .filter_map(|item| {
            if let syn::TraitItem::Fn(method) = item {
                Some(method.sig.ident.to_string())
            } else {
                None
            }
        })
        .collect();

    Some(RustDecl {
        name: item_trait.ident.to_string(),
        type_: "trait".to_string(),
        start_line,
        end_line,
        visibility: visibility_to_string(&item_trait.vis),
        is_async: false,
        is_unsafe: false,
        generics: item_trait
            .generics
            .params
            .iter()
            .map(|param| param.to_string())
            .collect(),
        traits: Vec::new(),
        fields: Vec::new(),
        methods,
        return_type: None,
        parameters: Vec::new(),
    })
}

fn parse_impl(item_impl: ItemImpl, content: &str) -> Option<RustDecl> {
    let start_line = item_impl.span().start().line;
    let end_line = item_impl.span().end().line;

    let target = type_to_string(&item_impl.self_ty);
    let methods: Vec<String> = item_impl
        .items
        .iter()
        .filter_map(|item| {
            if let syn::ImplItem::Fn(method) = item {
                Some(method.sig.ident.to_string())
            } else {
                None
            }
        })
        .collect();

    let traits: Vec<String> = item_impl
        .trait_
        .as_ref()
        .map(|(_, path, _)| path_to_string(path))
        .into_iter()
        .collect();

    Some(RustDecl {
        name: format!("impl_{}", target),
        type_: "impl".to_string(),
        start_line,
        end_line,
        visibility: "".to_string(),
        is_async: false,
        is_unsafe: item_impl.unsafety.is_some(),
        generics: item_impl
            .generics
            .params
            .iter()
            .map(|param| param.to_string())
            .collect(),
        traits,
        fields: Vec::new(),
        methods,
        return_type: None,
        parameters: Vec::new(),
    })
}

fn parse_mod(item_mod: syn::ItemMod, content: &str) -> Option<RustDecl> {
    let start_line = item_mod.span().start().line;
    let end_line = item_mod.span().end().line;

    Some(RustDecl {
        name: item_mod.ident.to_string(),
        type_: "module".to_string(),
        start_line,
        end_line,
        visibility: visibility_to_string(&item_mod.vis),
        is_async: false,
        is_unsafe: false,
        generics: Vec::new(),
        traits: Vec::new(),
        fields: Vec::new(),
        methods: Vec::new(),
        return_type: None,
        parameters: Vec::new(),
    })
}

fn visibility_to_string(vis: &Visibility) -> String {
    match vis {
        Visibility::Public(_) => "pub".to_string(),
        _ => "private".to_string(),
    }
}

fn type_to_string(ty: &Type) -> String {
    format!("{}", quote::quote!(#ty))
}

fn path_to_string(path: &syn::Path) -> String {
    format!("{}", quote::quote!(#path))
}