fix(esm-library): handle CSS modules in preserveModules (#13670)

CSS modules (native `experiments.css` or mini-css-extract) under
`output.library.preserveModules` caused either "chunk xxx should have at
least one file" or "Multiple assets emit different content to the same
filename". preserveModules set the JS filename_template on CSS chunks,
left chunks nameless so multiple CSS files collapsed onto `.css`, and
the ESM render phase emitted `import "__RSPACK_ESM_CHUNK_<id>"`
placeholders pointing at CSS-only chunks with no JS file.

Classify modules in preserve_modules by source_types and set
css_filename_template for CSS modules (preserving the `.css` extension
and source path), skip CSS-only modules/chunks in the ESM render paths
that emit JS-side requires / cross-chunk imports, and make
CssExtractRspackPlugin honor chunk.css_filename_template so preserveModules
can override its per-chunk filename.

Author: JSerFeng

crates/rspack_core/src/normal_module.rs

@@ -304,6 +304,14 @@ impl NormalModule {
   pub fn get_generator_options(&self) -> Option<&GeneratorOptions> {
     self.generator_options.as_ref()
   }
+
+  pub fn get_generator_options_mut(&mut self) -> Option<&mut GeneratorOptions> {
+    self.generator_options.as_mut()
+  }
+
+  pub fn set_generator_options(&mut self, generator_options: Option<GeneratorOptions>) {
+    self.generator_options = generator_options;
+  }
 }
 
 impl Identifiable for NormalModule {

crates/rspack_core/src/options/module.rs

@@ -544,6 +544,22 @@ impl GeneratorOptions {
       .or_else(|| self.get_asset_resource().and_then(|x| x.filename.as_ref()))
   }
 
+  /// Sets the asset filename on `Asset` / `AssetResource` variants. Returns
+  /// `true` if the variant supports a per-module filename and it was set.
+  pub fn set_asset_filename(&mut self, filename: Filename) -> bool {
+    match self {
+      Self::Asset(opts) => {
+        opts.filename = Some(filename);
+        true
+      }
+      Self::AssetResource(opts) => {
+        opts.filename = Some(filename);
+        true
+      }
+      _ => false,
+    }
+  }
+
   pub fn asset_output_path(&self) -> Option<&Filename> {
     self
       .get_asset()
@@ -630,7 +646,7 @@ impl Default for AssetGeneratorImportMode {
 }
 
 #[cacheable]
-#[derive(Debug, Clone, MergeFrom)]
+#[derive(Debug, Clone, Default, MergeFrom)]
 pub struct AssetResourceGeneratorOptions {
   pub emit: Option<bool>,
   pub filename: Option<Filename>,
@@ -654,7 +670,7 @@ impl From<AssetGeneratorOptions> for AssetResourceGeneratorOptions {
 }
 
 #[cacheable]
-#[derive(Debug, Clone, MergeFrom)]
+#[derive(Debug, Clone, Default, MergeFrom)]
 pub struct AssetGeneratorOptions {
   pub emit: Option<bool>,
   pub filename: Option<Filename>,