Format modules defined in cfg_attr (#3604)

Author: topecongiro

src/attr.rs

@@ -488,3 +488,36 @@ fn attr_prefix(attr: &ast::Attribute) -> &'static str {
         ast::AttrStyle::Outer => "#",
     }
 }
+
+pub(crate) trait MetaVisitor<'ast> {
+    fn visit_meta_item(&mut self, meta_item: &'ast ast::MetaItem) {
+        match meta_item.node {
+            ast::MetaItemKind::Word => self.visit_meta_word(meta_item),
+            ast::MetaItemKind::List(ref list) => self.visit_meta_list(meta_item, list),
+            ast::MetaItemKind::NameValue(ref lit) => self.visit_meta_name_value(meta_item, lit),
+        }
+    }
+
+    fn visit_meta_list(
+        &mut self,
+        _meta_item: &'ast ast::MetaItem,
+        list: &'ast [ast::NestedMetaItem],
+    ) {
+        for nm in list {
+            self.visit_nested_meta_item(nm);
+        }
+    }
+
+    fn visit_meta_word(&mut self, _meta_item: &'ast ast::MetaItem) {}
+
+    fn visit_meta_name_value(&mut self, _meta_item: &'ast ast::MetaItem, _lit: &'ast ast::Lit) {}
+
+    fn visit_nested_meta_item(&mut self, nm: &'ast ast::NestedMetaItem) {
+        match nm {
+            ast::NestedMetaItem::MetaItem(ref meta_item) => self.visit_meta_item(meta_item),
+            ast::NestedMetaItem::Literal(ref lit) => self.visit_literal(lit),
+        }
+    }
+
+    fn visit_literal(&mut self, _lit: &'ast ast::Lit) {}
+}

src/formatting.rs

@@ -105,7 +105,7 @@ fn format_project<T: FormatHandler>(
     )
     .visit_crate(&krate)
     .map_err(|e| io::Error::new(io::ErrorKind::Other, e))?;
-    for (path, (module, _)) in files {
+    for (path, module) in files {
         let should_ignore = !input_is_stdin && ignore_path_set.is_match(&path);
         if (config.skip_children() && path != main_file) || should_ignore {
             continue;