feat(css/parser): Support new nesting spec (#6337)

crates/swc_css_ast/src/base.rs

@@ -4,7 +4,7 @@ use swc_common::{ast_node, EqIgnoreSpan, Span};
 use crate::{
     AlphaValue, AtRule, CalcSum, CmykComponent, Color, ComplexSelector, DashedIdent, Delimiter,
     Dimension, Hue, Ident, Integer, KeyframeBlock, LayerName, Number, Percentage, Ratio,
-    SelectorList, Str, TokenAndSpan, UnicodeRange, Url,
+    RelativeSelectorList, SelectorList, Str, TokenAndSpan, UnicodeRange, Url,
 };
 
 #[ast_node("Stylesheet")]
@@ -38,10 +38,12 @@ pub struct QualifiedRule {
 #[ast_node]
 #[derive(Eq, Hash, Is, EqIgnoreSpan)]
 pub enum QualifiedRulePrelude {
-    #[tag("ListOfComponentValues")]
-    ListOfComponentValues(ListOfComponentValues),
     #[tag("SelectorList")]
     SelectorList(SelectorList),
+    #[tag("RelativeSelectorList")]
+    RelativeSelectorList(RelativeSelectorList),
+    #[tag("ListOfComponentValues")]
+    ListOfComponentValues(ListOfComponentValues),
 }
 
 #[ast_node]

crates/swc_css_codegen/src/lib.rs

@@ -93,6 +93,10 @@ where
                 emit!(self, n);
                 formatting_space!(self);
             }
+            QualifiedRulePrelude::RelativeSelectorList(n) => {
+                emit!(self, n);
+                formatting_space!(self);
+            }
             QualifiedRulePrelude::ListOfComponentValues(n) => {
                 emit!(
                     &mut *self.with_ctx(Ctx {

crates/swc_css_codegen/tests/fixture/style-blocks-contents/basic/output.css

@@ -24,8 +24,7 @@
 .foo {
   color: red;
   @media (min-width: 480px) {
-    & h1, 
-    & h2 {
+    & h1, & h2 {
       color: blue;
     }
   }

crates/swc_css_codegen/tests/fixture/style-blocks-contents/hacks/output.css

@@ -83,8 +83,8 @@ body:first-of-type .selector {}
   $property: value;color: red;
 }
 .selector {
-  color: red;
-  &property: value;}
+  &property: value;color: red;
+}
 .selector {
   *property: value;color: red;
 }