//! Processes out #[cfg] and #[cfg_attr] attributes from the input for the derive macro
use rustc_hash::FxHashSet;
use syntax::{
ast::{self, Attr, HasAttrs, Meta, VariantList},
AstNode, SyntaxElement, SyntaxNode, T,
};
use tracing::{info, warn};
use crate::{db::ExpandDatabase, MacroCallKind, MacroCallLoc};
fn check_cfg_attr(attr: &Attr, loc: &MacroCallLoc, db: &dyn ExpandDatabase) -> Option<bool> {
if !attr.simple_name().as_deref().map(|v| v == "cfg")? {
return None;
}
info!("Evaluating cfg {}", attr);
let cfg = cfg::CfgExpr::parse_from_attr_meta(attr.meta()?)?;
info!("Checking cfg {:?}", cfg);
let enabled = db.crate_graph()[loc.krate].cfg_options.check(&cfg) != Some(false);
Some(enabled)
}
fn check_cfg_attr_attr(attr: &Attr, loc: &MacroCallLoc, db: &dyn ExpandDatabase) -> Option<bool> {
if !attr.simple_name().as_deref().map(|v| v == "cfg_attr")? {
return None;
}
info!("Evaluating cfg_attr {}", attr);
let cfg_expr = cfg::CfgExpr::parse_from_attr_meta(attr.meta()?)?;
info!("Checking cfg_attr {:?}", cfg_expr);
let enabled = db.crate_graph()[loc.krate].cfg_options.check(&cfg_expr) != Some(false);
Some(enabled)
}
fn process_has_attrs_with_possible_comma<I: HasAttrs>(
items: impl Iterator<Item = I>,
loc: &MacroCallLoc,
db: &dyn ExpandDatabase,
remove: &mut FxHashSet<SyntaxElement>,
) -> Option<()> {
for item in items {
let field_attrs = item.attrs();
'attrs: for attr in field_attrs {
if let Some(enabled) = check_cfg_attr(&attr, loc, db) {
// Rustc does not strip the attribute if it is enabled. So we will will leave it
if !enabled {
info!("censoring type {:?}", item.syntax());
remove.insert(item.syntax().clone().into());
// We need to remove the , as well
add_comma(&item, remove);
break 'attrs;
}
};
if let Some(enabled) = check_cfg_attr_attr(&attr, loc, db) {
if enabled {
info!("Removing cfg_attr tokens {:?}", attr);
let meta = attr.meta()?;
let removes_from_cfg_attr = remove_tokens_within_cfg_attr(meta)?;
remove.extend(removes_from_cfg_attr);
} else {
info!("censoring type cfg_attr {:?}", item.syntax());
remove.insert(attr.syntax().clone().into());
continue;
}
}
}
}
Some(())
}
fn remove_tokens_within_cfg_attr(meta: Meta) -> Option<FxHashSet<SyntaxElement>> {
let mut remove: FxHashSet<SyntaxElement> = FxHashSet::default();
info!("Enabling attribute {}", meta);
let meta_path = meta.path()?;
info!("Removing {:?}", meta_path.syntax());
remove.insert(meta_path.syntax().clone().into());
let meta_tt = meta.token_tree()?;
info!("meta_tt {}", meta_tt);
// Remove the left paren
remove.insert(meta_tt.l_paren_token()?.into());
let mut found_comma = false;
for tt in meta_tt.token_trees_and_tokens().skip(1) {
info!("Checking {:?}", tt);
// Check if it is a subtree or a token. If it is a token check if it is a comma. If so, remove it and break.
match tt {
syntax::NodeOrToken::Node(node) => {
// Remove the entire subtree
remove.insert(node.syntax().clone().into());
}
syntax::NodeOrToken::Token(token) => {
if token.kind() == T![,] {
found_comma = true;
remove.insert(token.into());
break;
}
remove.insert(token.into());
}
}
}
if !found_comma {
warn!("No comma found in {}", meta_tt);
return None;
}
// Remove the right paren
remove.insert(meta_tt.r_paren_token()?.into());
Some(remove)
}
fn add_comma(item: &impl AstNode, res: &mut FxHashSet<SyntaxElement>) {
if let Some(comma) = item.syntax().next_sibling_or_token().filter(|it| it.kind() == T![,]) {
res.insert(comma);
}
}
fn process_enum(
variants: VariantList,
loc: &MacroCallLoc,
db: &dyn ExpandDatabase,
remove: &mut FxHashSet<SyntaxElement>,
) -> Option<()> {
'variant: for variant in variants.variants() {
for attr in variant.attrs() {
if let Some(enabled) = check_cfg_attr(&attr, loc, db) {
// Rustc does not strip the attribute if it is enabled. So we will will leave it
if !enabled {
info!("censoring type {:?}", variant.syntax());
remove.insert(variant.syntax().clone().into());
// We need to remove the , as well
add_comma(&variant, remove);
continue 'variant;
}
};
if let Some(enabled) = check_cfg_attr_attr(&attr, loc, db) {
if enabled {
info!("Removing cfg_attr tokens {:?}", attr);
let meta = attr.meta()?;
let removes_from_cfg_attr = remove_tokens_within_cfg_attr(meta)?;
remove.extend(removes_from_cfg_attr);
} else {
info!("censoring type cfg_attr {:?}", variant.syntax());
remove.insert(attr.syntax().clone().into());
continue;
}
}
}
if let Some(fields) = variant.field_list() {
match fields {
ast::FieldList::RecordFieldList(fields) => {
process_has_attrs_with_possible_comma(fields.fields(), loc, db, remove)?;
}
ast::FieldList::TupleFieldList(fields) => {
process_has_attrs_with_possible_comma(fields.fields(), loc, db, remove)?;
}
}
}
}
Some(())
}
pub(crate) fn process_cfg_attrs(
node: &SyntaxNode,
loc: &MacroCallLoc,
db: &dyn ExpandDatabase,
) -> Option<FxHashSet<SyntaxElement>> {
// FIXME: #[cfg_eval] is not implemented. But it is not stable yet
if !matches!(loc.kind, MacroCallKind::Derive { .. }) {
return None;
}
let mut res = FxHashSet::default();
let item = ast::Item::cast(node.clone())?;
match item {
ast::Item::Struct(it) => match it.field_list()? {
ast::FieldList::RecordFieldList(fields) => {
process_has_attrs_with_possible_comma(fields.fields(), loc, db, &mut res)?;
}
ast::FieldList::TupleFieldList(fields) => {
process_has_attrs_with_possible_comma(fields.fields(), loc, db, &mut res)?;
}
},
ast::Item::Enum(it) => {
process_enum(it.variant_list()?, loc, db, &mut res)?;
}
ast::Item::Union(it) => {
process_has_attrs_with_possible_comma(
it.record_field_list()?.fields(),
loc,
db,
&mut res,
)?;
}
// FIXME: Implement for other items if necessary. As we do not support #[cfg_eval] yet, we do not need to implement it for now
_ => {}
}
Some(res)
}