Handle lint attributes that are under #[cfg_attr]

Author: ChayimFriedman2

src/tools/rust-analyzer/crates/hir-expand/src/cfg_process.rs

@@ -6,7 +6,7 @@ use cfg::{CfgAtom, CfgExpr};
 use intern::{sym, Symbol};
 use rustc_hash::FxHashSet;
 use syntax::{
-    ast::{self, Attr, HasAttrs, Meta, VariantList},
+    ast::{self, Attr, HasAttrs, Meta, TokenTree, VariantList},
     AstNode, NodeOrToken, SyntaxElement, SyntaxKind, SyntaxNode, T,
 };
 use tracing::{debug, warn};
@@ -17,7 +17,7 @@ fn check_cfg(db: &dyn ExpandDatabase, attr: &Attr, krate: CrateId) -> Option<boo
     if !attr.simple_name().as_deref().map(|v| v == "cfg")? {
         return None;
     }
-    let cfg = parse_from_attr_meta(attr.meta()?)?;
+    let cfg = parse_from_attr_token_tree(&attr.meta()?.token_tree()?)?;
     let enabled = db.crate_graph()[krate].cfg_options.check(&cfg) != Some(false);
     Some(enabled)
 }
@@ -26,7 +26,15 @@ fn check_cfg_attr(db: &dyn ExpandDatabase, attr: &Attr, krate: CrateId) -> Optio
     if !attr.simple_name().as_deref().map(|v| v == "cfg_attr")? {
         return None;
     }
-    let cfg_expr = parse_from_attr_meta(attr.meta()?)?;
+    check_cfg_attr_value(db, &attr.token_tree()?, krate)
+}
+
+pub fn check_cfg_attr_value(
+    db: &dyn ExpandDatabase,
+    attr: &TokenTree,
+    krate: CrateId,
+) -> Option<bool> {
+    let cfg_expr = parse_from_attr_token_tree(attr)?;
     let enabled = db.crate_graph()[krate].cfg_options.check(&cfg_expr) != Some(false);
     Some(enabled)
 }
@@ -238,8 +246,7 @@ pub(crate) fn process_cfg_attrs(
     Some(remove)
 }
 /// Parses a `cfg` attribute from the meta
-fn parse_from_attr_meta(meta: Meta) -> Option<CfgExpr> {
-    let tt = meta.token_tree()?;
+fn parse_from_attr_token_tree(tt: &TokenTree) -> Option<CfgExpr> {
     let mut iter = tt
         .token_trees_and_tokens()
         .filter(is_not_whitespace)
@@ -328,7 +335,7 @@ mod tests {
     use expect_test::{expect, Expect};
     use syntax::{ast::Attr, AstNode, SourceFile};
 
-    use crate::cfg_process::parse_from_attr_meta;
+    use crate::cfg_process::parse_from_attr_token_tree;
 
     fn check_dnf_from_syntax(input: &str, expect: Expect) {
         let parse = SourceFile::parse(input, span::Edition::CURRENT);
@@ -342,7 +349,7 @@ mod tests {
         let node = node.clone_subtree();
         assert_eq!(node.syntax().text_range().start(), 0.into());
 
-        let cfg = parse_from_attr_meta(node.meta().unwrap()).unwrap();
+        let cfg = parse_from_attr_token_tree(&node.meta().unwrap().token_tree().unwrap()).unwrap();
         let actual = format!("#![cfg({})]", DnfExpr::new(&cfg));
         expect.assert_eq(&actual);
     }

src/tools/rust-analyzer/crates/hir-expand/src/lib.rs

@@ -53,6 +53,7 @@ use crate::{
 };
 
 pub use crate::{
+    cfg_process::check_cfg_attr_value,
     files::{AstId, ErasedAstId, FileRange, InFile, InMacroFile, InRealFile},
     prettify_macro_expansion_::prettify_macro_expansion,
 };

src/tools/rust-analyzer/crates/hir/src/semantics.rs

@@ -386,6 +386,19 @@ impl<'db> SemanticsImpl<'db> {
         Some(node)
     }
 
+    pub fn check_cfg_attr(&self, attr: &ast::TokenTree) -> Option<bool> {
+        let file_id = self.find_file(attr.syntax()).file_id;
+        let krate = match file_id.repr() {
+            HirFileIdRepr::FileId(file_id) => {
+                self.file_to_module_defs(file_id.file_id()).next()?.krate().id
+            }
+            HirFileIdRepr::MacroFile(macro_file) => {
+                self.db.lookup_intern_macro_call(macro_file.macro_call_id).krate
+            }
+        };
+        hir_expand::check_cfg_attr_value(self.db.upcast(), attr, krate)
+    }
+
     /// Expands the macro if it isn't one of the built-in ones that expand to custom syntax or dummy
     /// expansions.
     pub fn expand_allowed_builtins(&self, macro_call: &ast::MacroCall) -> Option<SyntaxNode> {

src/tools/rust-analyzer/crates/ide-diagnostics/src/handlers/incorrect_case.rs

@@ -997,6 +997,28 @@ fn BAR() {
         );
     }
 
+    #[test]
+    fn cfged_lint_attrs() {
+        check_diagnostics(
+            r#"
+//- /lib.rs cfg:feature=cool_feature
+#[cfg_attr(any(), allow(non_snake_case))]
+fn FOO() {}
+// ^^^ 💡 warn: Function `FOO` should have snake_case name, e.g. `foo`
+
+#[cfg_attr(non_existent, allow(non_snake_case))]
+fn BAR() {}
+// ^^^ 💡 warn: Function `BAR` should have snake_case name, e.g. `bar`
+
+#[cfg_attr(feature = "cool_feature", allow(non_snake_case))]
+fn BAZ() {}
+
+#[cfg_attr(feature = "cool_feature", cfg_attr ( all ( ) , allow ( non_snake_case ) ) ) ]
+fn QUX() {}
+        "#,
+        );
+    }
+
     #[test]
     fn allow_with_comment() {
         check_diagnostics(

src/tools/rust-analyzer/crates/ide-diagnostics/src/lib.rs

@@ -76,8 +76,9 @@ mod handlers {
 #[cfg(test)]
 mod tests;
 
-use std::{collections::hash_map, sync::LazyLock};
+use std::{collections::hash_map, iter, sync::LazyLock};
 
+use either::Either;
 use hir::{db::ExpandDatabase, diagnostics::AnyDiagnostic, Crate, HirFileId, InFile, Semantics};
 use ide_db::{
     assists::{Assist, AssistId, AssistKind, AssistResolveStrategy},
@@ -92,7 +93,7 @@ use ide_db::{
 use itertools::Itertools;
 use syntax::{
     ast::{self, AstNode, HasAttrs},
-    AstPtr, Edition, SmolStr, SyntaxNode, SyntaxNodePtr, TextRange,
+    AstPtr, Edition, NodeOrToken, SmolStr, SyntaxKind, SyntaxNode, SyntaxNodePtr, TextRange, T,
 };
 
 // FIXME: Make this an enum
@@ -647,6 +648,7 @@ fn find_outline_mod_lint_severity(
     let mut result = None;
     let lint_groups = lint_groups(&diag.code);
     lint_attrs(
+        sema,
         ast::AnyHasAttrs::cast(module_source_file.value).expect("SourceFile always has attrs"),
         edition,
     )
@@ -763,7 +765,7 @@ fn fill_lint_attrs(
 
             if let Some(ancestor) = ast::AnyHasAttrs::cast(ancestor) {
                 // Insert this node's attributes into any outline descendant, including this node.
-                lint_attrs(ancestor, edition).for_each(|(lint, severity)| {
+                lint_attrs(sema, ancestor, edition).for_each(|(lint, severity)| {
                     if diag_severity.is_none() && lint_groups(&diag.code).contains(&&*lint) {
                         diag_severity = Some(severity);
                     }
@@ -793,7 +795,7 @@ fn fill_lint_attrs(
             cache_stack.pop();
             return diag_severity;
         } else if let Some(ancestor) = ast::AnyHasAttrs::cast(ancestor) {
-            lint_attrs(ancestor, edition).for_each(|(lint, severity)| {
+            lint_attrs(sema, ancestor, edition).for_each(|(lint, severity)| {
                 if diag_severity.is_none() && lint_groups(&diag.code).contains(&&*lint) {
                     diag_severity = Some(severity);
                 }
@@ -809,20 +811,27 @@ fn fill_lint_attrs(
     }
 }
 
-fn lint_attrs(
+fn lint_attrs<'a>(
+    sema: &'a Semantics<'a, RootDatabase>,
     ancestor: ast::AnyHasAttrs,
     edition: Edition,
-) -> impl Iterator<Item = (SmolStr, Severity)> {
+) -> impl Iterator<Item = (SmolStr, Severity)> + 'a {
     ancestor
         .attrs_including_inner()
         .filter_map(|attr| {
             attr.as_simple_call().and_then(|(name, value)| match &*name {
-                "allow" | "expect" => Some((Severity::Allow, value)),
-                "warn" => Some((Severity::Warning, value)),
-                "forbid" | "deny" => Some((Severity::Error, value)),
+                "allow" | "expect" => Some(Either::Left(iter::once((Severity::Allow, value)))),
+                "warn" => Some(Either::Left(iter::once((Severity::Warning, value)))),
+                "forbid" | "deny" => Some(Either::Left(iter::once((Severity::Error, value)))),
+                "cfg_attr" => {
+                    let mut lint_attrs = Vec::new();
+                    cfg_attr_lint_attrs(sema, &value, &mut lint_attrs);
+                    Some(Either::Right(lint_attrs.into_iter()))
+                }
                 _ => None,
             })
         })
+        .flatten()
         .flat_map(move |(severity, lints)| {
             parse_tt_as_comma_sep_paths(lints, edition).into_iter().flat_map(move |lints| {
                 // Rejoin the idents with `::`, so we have no spaces in between.
@@ -836,6 +845,58 @@ fn lint_attrs(
         })
 }
 
+fn cfg_attr_lint_attrs(
+    sema: &Semantics<'_, RootDatabase>,
+    value: &ast::TokenTree,
+    lint_attrs: &mut Vec<(Severity, ast::TokenTree)>,
+) {
+    let prev_len = lint_attrs.len();
+
+    let mut iter = value.token_trees_and_tokens().filter(|it| match it {
+        NodeOrToken::Node(_) => true,
+        NodeOrToken::Token(it) => !it.kind().is_trivia(),
+    });
+
+    // Skip the condition.
+    for value in &mut iter {
+        if value.as_token().is_some_and(|it| it.kind() == T![,]) {
+            break;
+        }
+    }
+
+    while let Some(value) = iter.next() {
+        if let Some(token) = value.as_token() {
+            if token.kind() == SyntaxKind::IDENT {
+                let severity = match token.text() {
+                    "allow" | "expect" => Some(Severity::Allow),
+                    "warn" => Some(Severity::Warning),
+                    "forbid" | "deny" => Some(Severity::Error),
+                    "cfg_attr" => {
+                        if let Some(NodeOrToken::Node(value)) = iter.next() {
+                            cfg_attr_lint_attrs(sema, &value, lint_attrs);
+                        }
+                        None
+                    }
+                    _ => None,
+                };
+                if let Some(severity) = severity {
+                    let lints = iter.next();
+                    if let Some(NodeOrToken::Node(lints)) = lints {
+                        lint_attrs.push((severity, lints));
+                    }
+                }
+            }
+        }
+    }
+
+    if prev_len != lint_attrs.len() {
+        if let Some(false) | None = sema.check_cfg_attr(value) {
+            // Discard the attributes when the condition is false.
+            lint_attrs.truncate(prev_len);
+        }
+    }
+}
+
 fn lint_groups(lint: &DiagnosticCode) -> &'static [&'static str] {
     match lint {
         DiagnosticCode::RustcLint(name) => {