rust/crates/hir_expand/src/builtin_macro.rs

//! Builtin macro
use crate::{
    db::AstDatabase, name, quote, AstId, CrateId, EagerMacroId, LazyMacroId, MacroCallId,
    MacroDefId, MacroDefKind, TextSize,
};

use base_db::FileId;
use either::Either;
use mbe::parse_to_token_tree;
use parser::FragmentKind;
use syntax::ast::{self, AstToken};

macro_rules! register_builtin {
    ( LAZY: $(($name:ident, $kind: ident) => $expand:ident),* , EAGER: $(($e_name:ident, $e_kind: ident) => $e_expand:ident),*  ) => {
        #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
        pub enum BuiltinFnLikeExpander {
            $($kind),*
        }

        #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
        pub enum EagerExpander {
            $($e_kind),*
        }

        impl BuiltinFnLikeExpander {
            pub fn expand(
                &self,
                db: &dyn AstDatabase,
                id: LazyMacroId,
                tt: &tt::Subtree,
            ) -> Result<tt::Subtree, mbe::ExpandError> {
                let expander = match *self {
                    $( BuiltinFnLikeExpander::$kind => $expand, )*
                };
                expander(db, id, tt)
            }
        }

        impl EagerExpander {
            pub fn expand(
                &self,
                db: &dyn AstDatabase,
                arg_id: EagerMacroId,
                tt: &tt::Subtree,
            ) -> Result<(tt::Subtree, FragmentKind), mbe::ExpandError> {
                let expander = match *self {
                    $( EagerExpander::$e_kind => $e_expand, )*
                };
                expander(db,arg_id,tt)
            }
        }

        fn find_by_name(ident: &name::Name) -> Option<Either<BuiltinFnLikeExpander, EagerExpander>> {
            match ident {
                $( id if id == &name::name![$name] => Some(Either::Left(BuiltinFnLikeExpander::$kind)), )*
                $( id if id == &name::name![$e_name] => Some(Either::Right(EagerExpander::$e_kind)), )*
                _ => return None,
            }
        }
    };
}

pub fn find_builtin_macro(
    ident: &name::Name,
    krate: CrateId,
    ast_id: AstId<ast::MacroCall>,
) -> Option<MacroDefId> {
    let kind = find_by_name(ident)?;

    match kind {
        Either::Left(kind) => Some(MacroDefId {
            krate: Some(krate),
            ast_id: Some(ast_id),
            kind: MacroDefKind::BuiltIn(kind),
            local_inner: false,
        }),
        Either::Right(kind) => Some(MacroDefId {
            krate: Some(krate),
            ast_id: Some(ast_id),
            kind: MacroDefKind::BuiltInEager(kind),
            local_inner: false,
        }),
    }
}

register_builtin! {
    LAZY:
    (column, Column) => column_expand,
    (compile_error, CompileError) => compile_error_expand,
    (file, File) => file_expand,
    (line, Line) => line_expand,
    (assert, Assert) => assert_expand,
    (stringify, Stringify) => stringify_expand,
    (format_args, FormatArgs) => format_args_expand,
    // format_args_nl only differs in that it adds a newline in the end,
    // so we use the same stub expansion for now
    (format_args_nl, FormatArgsNl) => format_args_expand,

    EAGER:
    (concat, Concat) => concat_expand,
    (include, Include) => include_expand,
    (include_bytes, IncludeBytes) => include_bytes_expand,
    (include_str, IncludeStr) => include_str_expand,
    (env, Env) => env_expand,
    (option_env, OptionEnv) => option_env_expand
}

fn line_expand(
    _db: &dyn AstDatabase,
    _id: LazyMacroId,
    _tt: &tt::Subtree,
) -> Result<tt::Subtree, mbe::ExpandError> {
    // dummy implementation for type-checking purposes
    let line_num = 0;
    let expanded = quote! {
        #line_num
    };

    Ok(expanded)
}

fn stringify_expand(
    db: &dyn AstDatabase,
    id: LazyMacroId,
    _tt: &tt::Subtree,
) -> Result<tt::Subtree, mbe::ExpandError> {
    let loc = db.lookup_intern_macro(id);

    let macro_content = {
        let arg = loc.kind.arg(db).ok_or_else(|| mbe::ExpandError::UnexpectedToken)?;
        let macro_args = arg;
        let text = macro_args.text();
        let without_parens = TextSize::of('(')..text.len() - TextSize::of(')');
        text.slice(without_parens).to_string()
    };

    let expanded = quote! {
        #macro_content
    };

    Ok(expanded)
}

fn column_expand(
    _db: &dyn AstDatabase,
    _id: LazyMacroId,
    _tt: &tt::Subtree,
) -> Result<tt::Subtree, mbe::ExpandError> {
    // dummy implementation for type-checking purposes
    let col_num = 0;
    let expanded = quote! {
        #col_num
    };

    Ok(expanded)
}

fn assert_expand(
    _db: &dyn AstDatabase,
    _id: LazyMacroId,
    tt: &tt::Subtree,
) -> Result<tt::Subtree, mbe::ExpandError> {
    // A hacky implementation for goto def and hover
    // We expand `assert!(cond, arg1, arg2)` to
    // ```
    // {(cond, &(arg1), &(arg2));}
    // ```,
    // which is wrong but useful.

    let mut args = Vec::new();
    let mut current = Vec::new();
    for tt in tt.token_trees.iter().cloned() {
        match tt {
            tt::TokenTree::Leaf(tt::Leaf::Punct(p)) if p.char == ',' => {
                args.push(current);
                current = Vec::new();
            }
            _ => {
                current.push(tt);
            }
        }
    }
    if !current.is_empty() {
        args.push(current);
    }

    let arg_tts = args.into_iter().flat_map(|arg| {
        quote! { &(##arg), }
    }.token_trees).collect::<Vec<_>>();

    let expanded = quote! {
        { { (##arg_tts); } }
    };
    Ok(expanded)
}

fn file_expand(
    _db: &dyn AstDatabase,
    _id: LazyMacroId,
    _tt: &tt::Subtree,
) -> Result<tt::Subtree, mbe::ExpandError> {
    // FIXME: RA purposefully lacks knowledge of absolute file names
    // so just return "".
    let file_name = "";

    let expanded = quote! {
        #file_name
    };

    Ok(expanded)
}

fn compile_error_expand(
    _db: &dyn AstDatabase,
    _id: LazyMacroId,
    tt: &tt::Subtree,
) -> Result<tt::Subtree, mbe::ExpandError> {
    if tt.count() == 1 {
        if let tt::TokenTree::Leaf(tt::Leaf::Literal(it)) = &tt.token_trees[0] {
            let s = it.text.as_str();
            if s.contains('"') {
                return Ok(quote! { loop { #it }});
            }
        };
    }

    Err(mbe::ExpandError::BindingError("Must be a string".into()))
}

fn format_args_expand(
    _db: &dyn AstDatabase,
    _id: LazyMacroId,
    tt: &tt::Subtree,
) -> Result<tt::Subtree, mbe::ExpandError> {
    // We expand `format_args!("", a1, a2)` to
    // ```
    // std::fmt::Arguments::new_v1(&[], &[
    //   std::fmt::ArgumentV1::new(&arg1,std::fmt::Display::fmt),
    //   std::fmt::ArgumentV1::new(&arg2,std::fmt::Display::fmt),
    // ])
    // ```,
    // which is still not really correct, but close enough for now
    let mut args = Vec::new();
    let mut current = Vec::new();
    for tt in tt.token_trees.iter().cloned() {
        match tt {
            tt::TokenTree::Leaf(tt::Leaf::Punct(p)) if p.char == ',' => {
                args.push(current);
                current = Vec::new();
            }
            _ => {
                current.push(tt);
            }
        }
    }
    if !current.is_empty() {
        args.push(current);
    }
    if args.is_empty() {
        return Err(mbe::ExpandError::NoMatchingRule);
    }
    let _format_string = args.remove(0);
    let arg_tts = args.into_iter().flat_map(|arg| {
        quote! { std::fmt::ArgumentV1::new(&(##arg), std::fmt::Display::fmt), }
    }.token_trees).collect::<Vec<_>>();
    let expanded = quote! {
        std::fmt::Arguments::new_v1(&[], &[##arg_tts])
    };
    Ok(expanded)
}

fn unquote_str(lit: &tt::Literal) -> Option<String> {
    let lit = ast::make::tokens::literal(&lit.to_string());
    let token = ast::String::cast(lit)?;
    token.value().map(|it| it.into_owned())
}

fn concat_expand(
    _db: &dyn AstDatabase,
    _arg_id: EagerMacroId,
    tt: &tt::Subtree,
) -> Result<(tt::Subtree, FragmentKind), mbe::ExpandError> {
    let mut text = String::new();
    for (i, t) in tt.token_trees.iter().enumerate() {
        match t {
            tt::TokenTree::Leaf(tt::Leaf::Literal(it)) if i % 2 == 0 => {
                text += &unquote_str(&it).ok_or_else(|| mbe::ExpandError::ConversionError)?;
            }
            tt::TokenTree::Leaf(tt::Leaf::Punct(punct)) if i % 2 == 1 && punct.char == ',' => (),
            _ => return Err(mbe::ExpandError::UnexpectedToken),
        }
    }

    Ok((quote!(#text), FragmentKind::Expr))
}

fn relative_file(
    db: &dyn AstDatabase,
    call_id: MacroCallId,
    path: &str,
    allow_recursion: bool,
) -> Option<FileId> {
    let call_site = call_id.as_file().original_file(db);
    let res = db.resolve_path(call_site, path)?;
    // Prevent include itself
    if res == call_site && !allow_recursion {
        None
    } else {
        Some(res)
    }
}

fn parse_string(tt: &tt::Subtree) -> Result<String, mbe::ExpandError> {
    tt.token_trees
        .get(0)
        .and_then(|tt| match tt {
            tt::TokenTree::Leaf(tt::Leaf::Literal(it)) => unquote_str(&it),
            _ => None,
        })
        .ok_or_else(|| mbe::ExpandError::ConversionError)
}

fn include_expand(
    db: &dyn AstDatabase,
    arg_id: EagerMacroId,
    tt: &tt::Subtree,
) -> Result<(tt::Subtree, FragmentKind), mbe::ExpandError> {
    let path = parse_string(tt)?;
    let file_id = relative_file(db, arg_id.into(), &path, false)
        .ok_or_else(|| mbe::ExpandError::ConversionError)?;

    // FIXME:
    // Handle include as expression
    let res = parse_to_token_tree(&db.file_text(file_id))
        .ok_or_else(|| mbe::ExpandError::ConversionError)?
        .0;

    Ok((res, FragmentKind::Items))
}

fn include_bytes_expand(
    _db: &dyn AstDatabase,
    _arg_id: EagerMacroId,
    tt: &tt::Subtree,
) -> Result<(tt::Subtree, FragmentKind), mbe::ExpandError> {
    let _path = parse_string(tt)?;

    // FIXME: actually read the file here if the user asked for macro expansion
    let res = tt::Subtree {
        delimiter: None,
        token_trees: vec![tt::TokenTree::Leaf(tt::Leaf::Literal(tt::Literal {
            text: r#"b"""#.into(),
            id: tt::TokenId::unspecified(),
        }))],
    };
    Ok((res, FragmentKind::Expr))
}

fn include_str_expand(
    db: &dyn AstDatabase,
    arg_id: EagerMacroId,
    tt: &tt::Subtree,
) -> Result<(tt::Subtree, FragmentKind), mbe::ExpandError> {
    let path = parse_string(tt)?;

    // FIXME: we're not able to read excluded files (which is most of them because
    // it's unusual to `include_str!` a Rust file), but we can return an empty string.
    // Ideally, we'd be able to offer a precise expansion if the user asks for macro
    // expansion.
    let file_id = match relative_file(db, arg_id.into(), &path, true) {
        Some(file_id) => file_id,
        None => {
            return Ok((quote!(""), FragmentKind::Expr));
        }
    };

    let text = db.file_text(file_id);
    let text = &*text;

    Ok((quote!(#text), FragmentKind::Expr))
}

fn get_env_inner(db: &dyn AstDatabase, arg_id: EagerMacroId, key: &str) -> Option<String> {
    let krate = db.lookup_intern_eager_expansion(arg_id).krate;
    db.crate_graph()[krate].env.get(key)
}

fn env_expand(
    db: &dyn AstDatabase,
    arg_id: EagerMacroId,
    tt: &tt::Subtree,
) -> Result<(tt::Subtree, FragmentKind), mbe::ExpandError> {
    let key = parse_string(tt)?;

    // FIXME:
    // If the environment variable is not defined int rustc, then a compilation error will be emitted.
    // We might do the same if we fully support all other stuffs.
    // But for now on, we should return some dummy string for better type infer purpose.
    // However, we cannot use an empty string here, because for
    // `include!(concat!(env!("OUT_DIR"), "/foo.rs"))` will become
    // `include!("foo.rs"), which might go to infinite loop
    let s = get_env_inner(db, arg_id, &key).unwrap_or_else(|| "__RA_UNIMPLEMENTED__".to_string());
    let expanded = quote! { #s };

    Ok((expanded, FragmentKind::Expr))
}

fn option_env_expand(
    db: &dyn AstDatabase,
    arg_id: EagerMacroId,
    tt: &tt::Subtree,
) -> Result<(tt::Subtree, FragmentKind), mbe::ExpandError> {
    let key = parse_string(tt)?;
    let expanded = match get_env_inner(db, arg_id, &key) {
        None => quote! { std::option::Option::None::<&str> },
        Some(s) => quote! { std::option::Some(#s) },
    };

    Ok((expanded, FragmentKind::Expr))
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::{
        name::AsName, test_db::TestDB, AstNode, EagerCallLoc, MacroCallId, MacroCallKind,
        MacroCallLoc,
    };
    use base_db::{fixture::WithFixture, SourceDatabase};
    use std::sync::Arc;
    use syntax::ast::NameOwner;

    fn expand_builtin_macro(ra_fixture: &str) -> String {
        let (db, file_id) = TestDB::with_single_file(&ra_fixture);
        let parsed = db.parse(file_id);
        let macro_calls: Vec<_> =
            parsed.syntax_node().descendants().filter_map(ast::MacroCall::cast).collect();

        let ast_id_map = db.ast_id_map(file_id.into());

        let expander = find_by_name(&macro_calls[0].name().unwrap().as_name()).unwrap();

        let krate = CrateId(0);
        let file_id = match expander {
            Either::Left(expander) => {
                // the first one should be a macro_rules
                let def = MacroDefId {
                    krate: Some(CrateId(0)),
                    ast_id: Some(AstId::new(file_id.into(), ast_id_map.ast_id(&macro_calls[0]))),
                    kind: MacroDefKind::BuiltIn(expander),
                    local_inner: false,
                };

                let loc = MacroCallLoc {
                    def,
                    krate,
                    kind: MacroCallKind::FnLike(AstId::new(
                        file_id.into(),
                        ast_id_map.ast_id(&macro_calls[1]),
                    )),
                };

                let id: MacroCallId = db.intern_macro(loc).into();
                id.as_file()
            }
            Either::Right(expander) => {
                // the first one should be a macro_rules
                let def = MacroDefId {
                    krate: Some(krate),
                    ast_id: Some(AstId::new(file_id.into(), ast_id_map.ast_id(&macro_calls[0]))),
                    kind: MacroDefKind::BuiltInEager(expander),
                    local_inner: false,
                };

                let args = macro_calls[1].token_tree().unwrap();
                let parsed_args = mbe::ast_to_token_tree(&args).unwrap().0;

                let arg_id = db.intern_eager_expansion({
                    EagerCallLoc {
                        def,
                        fragment: FragmentKind::Expr,
                        subtree: Arc::new(parsed_args.clone()),
                        krate,
                        file_id: file_id.into(),
                    }
                });

                let (subtree, fragment) = expander.expand(&db, arg_id, &parsed_args).unwrap();
                let eager = EagerCallLoc {
                    def,
                    fragment,
                    subtree: Arc::new(subtree),
                    krate,
                    file_id: file_id.into(),
                };

                let id: MacroCallId = db.intern_eager_expansion(eager).into();
                id.as_file()
            }
        };

        db.parse_or_expand(file_id).unwrap().to_string()
    }

    #[test]
    fn test_column_expand() {
        let expanded = expand_builtin_macro(
            r#"
            #[rustc_builtin_macro]
            macro_rules! column {() => {}}
            column!()
            "#,
        );

        assert_eq!(expanded, "0");
    }

    #[test]
    fn test_line_expand() {
        let expanded = expand_builtin_macro(
            r#"
            #[rustc_builtin_macro]
            macro_rules! line {() => {}}
            line!()
            "#,
        );

        assert_eq!(expanded, "0");
    }

    #[test]
    fn test_stringify_expand() {
        let expanded = expand_builtin_macro(
            r#"
            #[rustc_builtin_macro]
            macro_rules! stringify {() => {}}
            stringify!(a b c)
            "#,
        );

        assert_eq!(expanded, "\"a b c\"");
    }

    #[test]
    fn test_env_expand() {
        let expanded = expand_builtin_macro(
            r#"
            #[rustc_builtin_macro]
            macro_rules! env {() => {}}
            env!("TEST_ENV_VAR")
            "#,
        );

        assert_eq!(expanded, "\"__RA_UNIMPLEMENTED__\"");
    }

    #[test]
    fn test_option_env_expand() {
        let expanded = expand_builtin_macro(
            r#"
            #[rustc_builtin_macro]
            macro_rules! option_env {() => {}}
            option_env!("TEST_ENV_VAR")
            "#,
        );

        assert_eq!(expanded, "std::option::Option::None:: < &str>");
    }

    #[test]
    fn test_file_expand() {
        let expanded = expand_builtin_macro(
            r#"
            #[rustc_builtin_macro]
            macro_rules! file {() => {}}
            file!()
            "#,
        );

        assert_eq!(expanded, "\"\"");
    }

    #[test]
    fn test_assert_expand() {
        let expanded = expand_builtin_macro(
            r#"
            #[rustc_builtin_macro]
            macro_rules! assert {
                ($cond:expr) => ({ /* compiler built-in */ });
                ($cond:expr, $($args:tt)*) => ({ /* compiler built-in */ })
            }
            assert!(true, "{} {:?}", arg1(a, b, c), arg2);
            "#,
        );

        assert_eq!(expanded, "{{(&(true), &(\"{} {:?}\"), &(arg1(a,b,c)), &(arg2),);}}");
    }

    #[test]
    fn test_compile_error_expand() {
        let expanded = expand_builtin_macro(
            r#"
            #[rustc_builtin_macro]
            macro_rules! compile_error {
                ($msg:expr) => ({ /* compiler built-in */ });
                ($msg:expr,) => ({ /* compiler built-in */ })
            }
            compile_error!("error!");
            "#,
        );

        assert_eq!(expanded, r#"loop{"error!"}"#);
    }

    #[test]
    fn test_format_args_expand() {
        let expanded = expand_builtin_macro(
            r#"
            #[rustc_builtin_macro]
            macro_rules! format_args {
                ($fmt:expr) => ({ /* compiler built-in */ });
                ($fmt:expr, $($args:tt)*) => ({ /* compiler built-in */ })
            }
            format_args!("{} {:?}", arg1(a, b, c), arg2);
            "#,
        );

        assert_eq!(
            expanded,
            r#"std::fmt::Arguments::new_v1(&[], &[std::fmt::ArgumentV1::new(&(arg1(a,b,c)),std::fmt::Display::fmt),std::fmt::ArgumentV1::new(&(arg2),std::fmt::Display::fmt),])"#
        );
    }

    #[test]
    fn test_include_bytes_expand() {
        let expanded = expand_builtin_macro(
            r#"
            #[rustc_builtin_macro]
            macro_rules! include_bytes {
                ($file:expr) => {{ /* compiler built-in */ }};
                ($file:expr,) => {{ /* compiler built-in */ }};
            }
            include_bytes("foo");
            "#,
        );

        assert_eq!(expanded, r#"b"""#);
    }
}