use rustc_ast::ptr::P;
use rustc_ast::token::{Delimiter, Token, TokenKind};
use rustc_ast::tokenstream::{
AttrTokenStream, AttrTokenTree, LazyAttrTokenStream, Spacing, TokenTree,
};
use rustc_ast::{
self as ast, AttrStyle, Attribute, HasAttrs, HasTokens, MetaItem, NestedMetaItem, NodeId,
};
use rustc_attr as attr;
use rustc_data_structures::flat_map_in_place::FlatMapInPlace;
use rustc_feature::{
ACCEPTED_FEATURES, AttributeSafety, Features, REMOVED_FEATURES, UNSTABLE_FEATURES,
};
use rustc_lint_defs::BuiltinLintDiag;
use rustc_parse::validate_attr;
use rustc_session::Session;
use rustc_session::parse::feature_err;
use rustc_span::Span;
use rustc_span::symbol::{Symbol, sym};
use thin_vec::ThinVec;
use tracing::instrument;
use crate::errors::{
CrateNameInCfgAttr, CrateTypeInCfgAttr, FeatureNotAllowed, FeatureRemoved,
FeatureRemovedReason, InvalidCfg, MalformedFeatureAttribute, MalformedFeatureAttributeHelp,
RemoveExprNotSupported,
};
pub struct StripUnconfigured<'a> {
pub sess: &'a Session,
pub features: Option<&'a Features>,
pub config_tokens: bool,
pub lint_node_id: NodeId,
}
pub fn features(sess: &Session, krate_attrs: &[Attribute], crate_name: Symbol) -> Features {
fn feature_list(attr: &Attribute) -> ThinVec<ast::NestedMetaItem> {
if attr.has_name(sym::feature)
&& let Some(list) = attr.meta_item_list()
{
list
} else {
ThinVec::new()
}
}
let mut features = Features::default();
for attr in krate_attrs {
for mi in feature_list(attr) {
let name = match mi.ident() {
Some(ident) if mi.is_word() => ident.name,
Some(ident) => {
sess.dcx().emit_err(MalformedFeatureAttribute {
span: mi.span(),
help: MalformedFeatureAttributeHelp::Suggestion {
span: mi.span(),
suggestion: ident.name,
},
});
continue;
}
None => {
sess.dcx().emit_err(MalformedFeatureAttribute {
span: mi.span(),
help: MalformedFeatureAttributeHelp::Label { span: mi.span() },
});
continue;
}
};
if let Some(f) = REMOVED_FEATURES.iter().find(|f| name == f.feature.name) {
sess.dcx().emit_err(FeatureRemoved {
span: mi.span(),
reason: f.reason.map(|reason| FeatureRemovedReason { reason }),
});
continue;
}
if let Some(f) = ACCEPTED_FEATURES.iter().find(|f| name == f.name) {
let since = Some(Symbol::intern(f.since));
features.set_declared_lang_feature(name, mi.span(), since);
continue;
}
if let Some(allowed) = sess.opts.unstable_opts.allow_features.as_ref() {
if allowed.iter().all(|f| name.as_str() != f) {
sess.dcx().emit_err(FeatureNotAllowed { span: mi.span(), name });
continue;
}
}
if let Some(f) = UNSTABLE_FEATURES.iter().find(|f| name == f.feature.name) {
(f.set_enabled)(&mut features);
if features.internal(name)
&& ![sym::core, sym::alloc, sym::std].contains(&crate_name)
{
sess.using_internal_features.store(true, std::sync::atomic::Ordering::Relaxed);
}
features.set_declared_lang_feature(name, mi.span(), None);
continue;
}
features.set_declared_lib_feature(name, mi.span());
if features.internal(name) && ![sym::core, sym::alloc, sym::std].contains(&crate_name) {
sess.using_internal_features.store(true, std::sync::atomic::Ordering::Relaxed);
}
}
}
features
}
pub fn pre_configure_attrs(sess: &Session, attrs: &[Attribute]) -> ast::AttrVec {
let strip_unconfigured = StripUnconfigured {
sess,
features: None,
config_tokens: false,
lint_node_id: ast::CRATE_NODE_ID,
};
attrs
.iter()
.flat_map(|attr| strip_unconfigured.process_cfg_attr(attr))
.take_while(|attr| !is_cfg(attr) || strip_unconfigured.cfg_true(attr).0)
.collect()
}
#[macro_export]
macro_rules! configure {
($this:ident, $node:ident) => {
match $this.configure($node) {
Some(node) => node,
None => return Default::default(),
}
};
}
impl<'a> StripUnconfigured<'a> {
pub fn configure<T: HasAttrs + HasTokens>(&self, mut node: T) -> Option<T> {
self.process_cfg_attrs(&mut node);
self.in_cfg(node.attrs()).then(|| {
self.try_configure_tokens(&mut node);
node
})
}
fn try_configure_tokens<T: HasTokens>(&self, node: &mut T) {
if self.config_tokens {
if let Some(Some(tokens)) = node.tokens_mut() {
let attr_stream = tokens.to_attr_token_stream();
*tokens = LazyAttrTokenStream::new(self.configure_tokens(&attr_stream));
}
}
}
fn configure_tokens(&self, stream: &AttrTokenStream) -> AttrTokenStream {
fn can_skip(stream: &AttrTokenStream) -> bool {
stream.0.iter().all(|tree| match tree {
AttrTokenTree::AttrsTarget(_) => false,
AttrTokenTree::Token(..) => true,
AttrTokenTree::Delimited(.., inner) => can_skip(inner),
})
}
if can_skip(stream) {
return stream.clone();
}
let trees: Vec<_> = stream
.0
.iter()
.filter_map(|tree| match tree.clone() {
AttrTokenTree::AttrsTarget(mut target) => {
target.attrs.flat_map_in_place(|attr| self.process_cfg_attr(&attr));
if self.in_cfg(&target.attrs) {
target.tokens = LazyAttrTokenStream::new(
self.configure_tokens(&target.tokens.to_attr_token_stream()),
);
Some(AttrTokenTree::AttrsTarget(target))
} else {
None
}
}
AttrTokenTree::Delimited(sp, spacing, delim, mut inner) => {
inner = self.configure_tokens(&inner);
Some(AttrTokenTree::Delimited(sp, spacing, delim, inner))
}
AttrTokenTree::Token(
Token {
kind:
TokenKind::NtIdent(..)
| TokenKind::NtLifetime(..)
| TokenKind::Interpolated(..),
..
},
_,
) => {
panic!("Nonterminal should have been flattened: {:?}", tree);
}
AttrTokenTree::Token(
Token { kind: TokenKind::OpenDelim(_) | TokenKind::CloseDelim(_), .. },
_,
) => {
panic!("Should be `AttrTokenTree::Delimited`, not delim tokens: {:?}", tree);
}
AttrTokenTree::Token(token, spacing) => Some(AttrTokenTree::Token(token, spacing)),
})
.collect();
AttrTokenStream::new(trees)
}
fn process_cfg_attrs<T: HasAttrs>(&self, node: &mut T) {
node.visit_attrs(|attrs| {
attrs.flat_map_in_place(|attr| self.process_cfg_attr(&attr));
});
}
fn process_cfg_attr(&self, attr: &Attribute) -> Vec<Attribute> {
if attr.has_name(sym::cfg_attr) {
self.expand_cfg_attr(attr, true)
} else {
vec![attr.clone()]
}
}
pub(crate) fn expand_cfg_attr(&self, cfg_attr: &Attribute, recursive: bool) -> Vec<Attribute> {
validate_attr::check_attribute_safety(&self.sess.psess, AttributeSafety::Normal, &cfg_attr);
let Some((cfg_predicate, expanded_attrs)) =
rustc_parse::parse_cfg_attr(cfg_attr, &self.sess.psess)
else {
return vec![];
};
if expanded_attrs.is_empty() {
self.sess.psess.buffer_lint(
rustc_lint_defs::builtin::UNUSED_ATTRIBUTES,
cfg_attr.span,
ast::CRATE_NODE_ID,
BuiltinLintDiag::CfgAttrNoAttributes,
);
}
if !attr::cfg_matches(&cfg_predicate, &self.sess, self.lint_node_id, self.features) {
return vec![];
}
if recursive {
expanded_attrs
.into_iter()
.flat_map(|item| self.process_cfg_attr(&self.expand_cfg_attr_item(cfg_attr, item)))
.collect()
} else {
expanded_attrs
.into_iter()
.map(|item| self.expand_cfg_attr_item(cfg_attr, item))
.collect()
}
}
fn expand_cfg_attr_item(
&self,
cfg_attr: &Attribute,
(item, item_span): (ast::AttrItem, Span),
) -> Attribute {
let mut orig_trees = cfg_attr.token_trees().into_iter();
let Some(TokenTree::Token(pound_token @ Token { kind: TokenKind::Pound, .. }, _)) =
orig_trees.next()
else {
panic!("Bad tokens for attribute {cfg_attr:?}");
};
let mut trees = if cfg_attr.style == AttrStyle::Inner {
let Some(TokenTree::Token(bang_token @ Token { kind: TokenKind::Not, .. }, _)) =
orig_trees.next()
else {
panic!("Bad tokens for attribute {cfg_attr:?}");
};
vec![
AttrTokenTree::Token(pound_token, Spacing::Joint),
AttrTokenTree::Token(bang_token, Spacing::JointHidden),
]
} else {
vec![AttrTokenTree::Token(pound_token, Spacing::JointHidden)]
};
let Some(TokenTree::Delimited(delim_span, delim_spacing, Delimiter::Bracket, _)) =
orig_trees.next()
else {
panic!("Bad tokens for attribute {cfg_attr:?}");
};
trees.push(AttrTokenTree::Delimited(
delim_span,
delim_spacing,
Delimiter::Bracket,
item.tokens
.as_ref()
.unwrap_or_else(|| panic!("Missing tokens for {item:?}"))
.to_attr_token_stream(),
));
let tokens = Some(LazyAttrTokenStream::new(AttrTokenStream::new(trees)));
let attr = attr::mk_attr_from_item(
&self.sess.psess.attr_id_generator,
item,
tokens,
cfg_attr.style,
item_span,
);
if attr.has_name(sym::crate_type) {
self.sess.dcx().emit_err(CrateTypeInCfgAttr { span: attr.span });
}
if attr.has_name(sym::crate_name) {
self.sess.dcx().emit_err(CrateNameInCfgAttr { span: attr.span });
}
attr
}
fn in_cfg(&self, attrs: &[Attribute]) -> bool {
attrs.iter().all(|attr| !is_cfg(attr) || self.cfg_true(attr).0)
}
pub(crate) fn cfg_true(&self, attr: &Attribute) -> (bool, Option<MetaItem>) {
let meta_item = match validate_attr::parse_meta(&self.sess.psess, attr) {
Ok(meta_item) => meta_item,
Err(err) => {
err.emit();
return (true, None);
}
};
validate_attr::deny_builtin_meta_unsafety(&self.sess.psess, &meta_item);
(
parse_cfg(&meta_item, self.sess).map_or(true, |meta_item| {
attr::cfg_matches(meta_item, &self.sess, self.lint_node_id, self.features)
}),
Some(meta_item),
)
}
#[instrument(level = "trace", skip(self))]
pub(crate) fn maybe_emit_expr_attr_err(&self, attr: &Attribute) {
if self.features.is_some_and(|features| !features.stmt_expr_attributes)
&& !attr.span.allows_unstable(sym::stmt_expr_attributes)
{
let mut err = feature_err(
&self.sess,
sym::stmt_expr_attributes,
attr.span,
crate::fluent_generated::expand_attributes_on_expressions_experimental,
);
if attr.is_doc_comment() {
err.help(if attr.style == AttrStyle::Outer {
crate::fluent_generated::expand_help_outer_doc
} else {
crate::fluent_generated::expand_help_inner_doc
});
}
err.emit();
}
}
#[instrument(level = "trace", skip(self))]
pub fn configure_expr(&self, expr: &mut P<ast::Expr>, method_receiver: bool) {
if !method_receiver {
for attr in expr.attrs.iter() {
self.maybe_emit_expr_attr_err(attr);
}
}
if let Some(attr) = expr.attrs().iter().find(|a| is_cfg(a)) {
self.sess.dcx().emit_err(RemoveExprNotSupported { span: attr.span });
}
self.process_cfg_attrs(expr);
self.try_configure_tokens(&mut *expr);
}
}
pub fn parse_cfg<'a>(meta_item: &'a MetaItem, sess: &Session) -> Option<&'a NestedMetaItem> {
let span = meta_item.span;
match meta_item.meta_item_list() {
None => {
sess.dcx().emit_err(InvalidCfg::NotFollowedByParens { span });
None
}
Some([]) => {
sess.dcx().emit_err(InvalidCfg::NoPredicate { span });
None
}
Some([_, .., l]) => {
sess.dcx().emit_err(InvalidCfg::MultiplePredicates { span: l.span() });
None
}
Some([single]) => match single.meta_item_or_bool() {
Some(meta_item) => Some(meta_item),
None => {
sess.dcx().emit_err(InvalidCfg::PredicateLiteral { span: single.span() });
None
}
},
}
}
fn is_cfg(attr: &Attribute) -> bool {
attr.has_name(sym::cfg)
}