fix: should not tree shaking used ident accidentally in composes (#9161)

fix: should not remove ident in composes

Author: JSerFeng

crates/rspack_plugin_css/src/parser_and_generator/mod.rs

@@ -24,7 +24,7 @@ use rspack_error::{
   miette::Diagnostic, IntoTWithDiagnosticArray, Result, RspackSeverity, TWithDiagnosticArray,
 };
 use rspack_util::ext::DynHash;
-use rustc_hash::FxHashSet;
+use rustc_hash::{FxHashMap, FxHashSet};
 
 use crate::{
   dependency::CssSelfReferenceLocalIdentDependency,
@@ -87,6 +87,7 @@ pub struct CssParserAndGenerator {
   pub es_module: bool,
   #[cacheable(with=AsOption<AsMap<AsCacheable, AsVec>>)]
   pub exports: Option<CssExports>,
+  pub local_names: Option<FxHashMap<String, String>>,
   pub hot: bool,
 }
 
@@ -243,6 +244,10 @@ impl ParserAndGenerator for CssParserAndGenerator {
               },
             );
           }
+
+          let local_names = self.local_names.get_or_insert_default();
+          local_names.insert(name.into_owned(), local_ident.clone());
+
           dependencies.push(Box::new(CssLocalIdentDependency::new(
             local_ident,
             convention_names,
@@ -315,6 +320,10 @@ impl ParserAndGenerator for CssParserAndGenerator {
               },
             );
           }
+
+          let local_names = self.local_names.get_or_insert_default();
+          local_names.insert(name.into_owned(), local_ident.clone());
+
           dependencies.push(Box::new(CssLocalIdentDependency::new(
             local_ident.clone(),
             convention_names,
@@ -355,6 +364,7 @@ impl ParserAndGenerator for CssParserAndGenerator {
               vec![],
             )));
           }
+
           let exports = self.exports.get_or_insert_default();
           for name in names {
             for local_class in local_classes.iter() {
@@ -494,8 +504,16 @@ impl ParserAndGenerator for CssParserAndGenerator {
           let mut concate_source = ConcatSource::default();
           if let Some(ref exports) = self.exports {
             let mg = generate_context.compilation.get_module_graph();
-            let unused_exports =
-              get_unused_local_ident(exports, module.identifier(), generate_context.runtime, &mg);
+            let unused_exports = get_unused_local_ident(
+              exports,
+              self
+                .local_names
+                .as_ref()
+                .expect("local names must be set when self.exports is set"),
+              module.identifier(),
+              generate_context.runtime,
+              &mg,
+            );
             generate_context.data.insert(unused_exports);
             let exports =
               get_used_exports(exports, module.identifier(), generate_context.runtime, &mg);
@@ -522,8 +540,16 @@ impl ParserAndGenerator for CssParserAndGenerator {
             ("", "", "")
           };
           if let Some(exports) = &self.exports {
-            let unused_exports =
-              get_unused_local_ident(exports, module.identifier(), generate_context.runtime, &mg);
+            let unused_exports = get_unused_local_ident(
+              exports,
+              self
+                .local_names
+                .as_ref()
+                .expect("local names must be set when self.exports is set"),
+              module.identifier(),
+              generate_context.runtime,
+              &mg,
+            );
             generate_context.data.insert(unused_exports);
 
             let exports =
@@ -625,6 +651,7 @@ pub struct CodeGenerationDataUnusedLocalIdent {
 
 fn get_unused_local_ident(
   exports: &CssExports,
+  local_names: &FxHashMap<String, String>,
   identifier: ModuleIdentifier,
   runtime: Option<&RuntimeSpec>,
   mg: &ModuleGraph,
@@ -641,11 +668,7 @@ fn get_unused_local_ident(
           false
         }
       })
-      .flat_map(|(_, exports)| {
-        exports
-          .iter()
-          .map(|export| unescape(&export.ident).into_owned())
-      })
+      .filter_map(|(export_name, _)| local_names.get(export_name).cloned())
       .collect(),
   }
 }

crates/rspack_plugin_css/src/plugin/impl_plugin_for_css_plugin.rs

@@ -425,6 +425,7 @@ impl Plugin for CssPlugin {
           .expect("should have CssGeneratorOptions");
         Box::new(CssParserAndGenerator {
           exports: None,
+          local_names: None,
           convention: None,
           local_ident_name: None,
           exports_only: g.exports_only.expect("should have exports_only"),
@@ -445,6 +446,7 @@ impl Plugin for CssPlugin {
           .expect("should have CssModuleGeneratorOptions");
         Box::new(CssParserAndGenerator {
           exports: None,
+          local_names: None,
           convention: Some(
             g.exports_convention
               .expect("should have exports_convention"),
@@ -472,6 +474,7 @@ impl Plugin for CssPlugin {
           .expect("should have CssAutoGeneratorOptions");
         Box::new(CssParserAndGenerator {
           exports: None,
+          local_names: None,
           convention: Some(
             g.exports_convention
               .expect("should have exports_convention"),

packages/rspack-test-tools/tests/configCases/css/minify-lightning-css-remove-unused-local-idents/index.js

@@ -4,12 +4,14 @@ it("should remove unused local idents", async () => {
 	const fs = __non_webpack_require__("fs");
 	const path = __non_webpack_require__("path");
 	expect(styles.a).toBe("./style.module-a");
-	expect(styles['local/used']).toBe("./style.module-local/used");
+	expect(styles["local/used"]).toBe("./style.module-local/used");
+	expect(styles["composed-local"]).toBe("./style.module-composed-local");
 
 	if (!EXPORTS_ONLY) {
 		const css = await fs.promises.readFile(path.resolve(__dirname, "./bundle0.css"), "utf-8");
 		expect(css).not.toContain(".module-b")
 		expect(css).toContain("local\\/used")
 		expect(css).not.toContain("local\\/unused")
+		expect(css).toContain("composed-local")
 	}
 })

packages/rspack-test-tools/tests/configCases/css/minify-lightning-css-remove-unused-local-idents/style.module.css

@@ -13,3 +13,11 @@
 .local\/unused {
   color: blue
 }
+
+.compose {
+  composes: composed-local;
+}
+
+.composed-local {
+  background-color: green;
+}