feat: add ExportsKind::None (#315)

<!-- Thank you for contributing! -->

### Description

<!-- Please insert your description here and provide especially info about the "what" this PR is solving -->

### Test Plan

<!-- e.g. is there anything you'd like reviewers to focus on? -->

---

crates/rolldown/src/bundler/module_loader/normal_module_task.rs

@@ -104,7 +104,7 @@ impl<'task, T: FileSystem + Default + 'static> NormalModuleTask<'task, T> {
       star_exports: Some(star_exports),
       default_export_symbol: export_default_symbol_id,
       scope: Some(scope),
-      exports_kind,
+      exports_kind: Some(exports_kind),
       namespace_symbol: Some(namespace_symbol),
       module_type: self.module_type,
       is_entry: self.is_entry,

crates/rolldown/src/bundler/module_loader/runtime_normal_module_task.rs

@@ -1,6 +1,6 @@
 use index_vec::IndexVec;
 use oxc::{ast::Visit, span::SourceType};
-use rolldown_common::{ModuleId, ModuleType, ResourceId, SymbolRef};
+use rolldown_common::{ExportsKind, ModuleId, ModuleType, ResourceId, SymbolRef};
 use rolldown_error::BuildError;
 use rolldown_oxc::{OxcCompiler, OxcProgram};
 
@@ -43,12 +43,12 @@ impl RuntimeNormalModuleTask {
       named_imports,
       named_exports,
       stmt_infos,
-      import_records: _,
       star_exports,
       export_default_symbol_id,
       imports,
-      exports_kind,
       unique_name,
+      import_records: _,
+      exports_kind: _,
     } = scan_result;
 
     builder.id = Some(self.module_id);
@@ -65,7 +65,7 @@ impl RuntimeNormalModuleTask {
     builder.default_export_symbol = export_default_symbol_id;
     builder.import_records = Some(IndexVec::default());
     builder.scope = Some(scope);
-    builder.exports_kind = exports_kind;
+    builder.exports_kind = Some(ExportsKind::Esm);
     builder.namespace_symbol = Some(namespace_symbol);
     builder.pretty_path = Some("<runtime>".to_string());
 

crates/rolldown/src/bundler/stages/link_stage.rs

@@ -57,7 +57,7 @@ impl LinkStage {
     }
   }
 
-  pub fn sort_modules(&mut self) {
+  fn sort_modules(&mut self) {
     let mut stack = self.entries.iter().map(|(_, m)| Action::Enter(*m)).rev().collect::<Vec<_>>();
     // The runtime module should always be the first module to be executed
     stack.push(Action::Enter(self.runtime.id()));

crates/rolldown/src/bundler/visitors/scanner.rs

@@ -29,7 +29,7 @@ pub struct ScanResult {
   pub star_exports: Vec<ImportRecordId>,
   pub export_default_symbol_id: Option<SymbolId>,
   pub imports: FxHashMap<Span, ImportRecordId>,
-  pub exports_kind: Option<ExportsKind>,
+  pub exports_kind: ExportsKind,
 }
 
 pub struct Scanner<'a> {
@@ -92,15 +92,15 @@ impl<'a> Scanner<'a> {
 
   fn set_exports_kind(&mut self) {
     if self.esm_export_keyword.is_some() {
-      self.result.exports_kind = Some(ExportsKind::Esm);
+      self.result.exports_kind = ExportsKind::Esm;
     } else if self.cjs_export_keyword.is_some() {
-      self.result.exports_kind = Some(ExportsKind::CommonJs);
+      self.result.exports_kind = ExportsKind::CommonJs;
     } else if self.module_type.is_esm() {
-      self.result.exports_kind = Some(ExportsKind::Esm);
+      self.result.exports_kind = ExportsKind::Esm;
     } else if self.module_type.is_commonjs() {
-      self.result.exports_kind = Some(ExportsKind::CommonJs);
+      self.result.exports_kind = ExportsKind::CommonJs;
     } else {
-      self.result.exports_kind = Some(ExportsKind::Esm);
+      self.result.exports_kind = ExportsKind::Esm;
     }
   }
 

crates/rolldown_common/src/exports_kind.rs

@@ -2,4 +2,11 @@
 pub enum ExportsKind {
   Esm,
   CommonJs,
+  None,
+}
+
+impl Default for ExportsKind {
+  fn default() -> Self {
+    Self::None
+  }
 }