feat: remove empty unneeded runtime chunk

Author: JSerFeng

crates/rspack_plugin_esm_library/src/plugin.rs

@@ -37,6 +37,8 @@ pub static CONCATENATED_MODULES_MAP: LazyLock<
 pub static LINKS: LazyLock<RwLock<FxHashMap<u32, UkeyMap<ChunkUkey, ChunkLinkContext>>>> =
   LazyLock::new(Default::default);
 
+pub static RSPACK_ESM_RUNTIME_CHUNK: &str = "RSPACK_ESM_RUNTIME";
+
 #[plugin]
 #[derive(Debug, Default)]
 pub struct EsmLibraryPlugin {}
@@ -355,12 +357,25 @@ static RSPACK_ESM_CHUNK_PLACEHOLDER_RE: LazyLock<Regex> =
 #[plugin_hook(CompilationProcessAssets for EsmLibraryPlugin, stage = Compilation::PROCESS_ASSETS_STAGE_AFTER_OPTIMIZE_HASH)]
 async fn process_assets(&self, compilation: &mut Compilation) -> Result<()> {
   let mut replaced = vec![];
+  let mut removed = vec![];
 
   for (asset_name, asset) in compilation.assets() {
     if asset.get_info().javascript_module.unwrap_or_default() {
       let Some(source) = asset.get_source() else {
         continue;
       };
+
+      if asset
+        .get_info()
+        .extras
+        .contains_key(RSPACK_ESM_RUNTIME_CHUNK)
+        && source.source().trim().is_empty()
+      {
+        // remove empty runtime chunk
+        removed.push(asset_name.to_string());
+        continue;
+      }
+
       let mut replace_source = ReplaceSource::new(source.clone());
       let output_path = compilation.options.output.path.as_std_path();
       let mut self_path = output_path.join(asset_name);
@@ -425,6 +440,9 @@ async fn process_assets(&self, compilation: &mut Compilation) -> Result<()> {
       .expect("should have asset")
       .set_source(Some(Arc::new(replace_source)));
   }
+  for remove_name in removed {
+    compilation.assets_mut().remove(&remove_name);
+  }
 
   Ok(())
 }

crates/rspack_plugin_esm_library/src/render.rs

@@ -26,7 +26,7 @@ use swc_core::common::sync::Lazy;
 
 use crate::{
   chunk_link::{ChunkLinkContext, Ref},
-  plugin::{CONCATENATED_MODULES_MAP, LINKS},
+  plugin::{CONCATENATED_MODULES_MAP, LINKS, RSPACK_ESM_RUNTIME_CHUNK},
   runtime::RegisterModuleRuntime,
 };
 
@@ -186,6 +186,9 @@ impl EsmLibraryPlugin {
 
     // render webpack runtime
     if chunk.has_runtime(&compilation.chunk_group_by_ukey) {
+      asset_info
+        .extras
+        .insert(RSPACK_ESM_RUNTIME_CHUNK.into(), "true".into());
       // render chunk needs to render *all* runtimes in the whole tree
       let tree_runtime_requirements =
         ChunkGraph::get_tree_runtime_requirements(compilation, chunk_ukey);

tests/rspack-test/esmOutputCases/deconflict/deconflit-local/__snapshots__/esm.snap.txt

@@ -16,10 +16,4 @@ it('should have deconflicted symbol', () => {
 })
 
 
-```
-
-```mjs title=runtime.mjs
-
-
-
 ```

tests/rspack-test/esmOutputCases/deconflict/other-chunk-local/__snapshots__/esm.snap.txt

@@ -33,10 +33,4 @@ const value = foo_value
 
 export { value };
 
-```
-
-```mjs title=runtime.mjs
-
-
-
 ```

tests/rspack-test/esmOutputCases/dynamic-import/import-self/__snapshots__/esm.snap.txt

@@ -12,12 +12,6 @@ it('should have access to the value from the same file', async () => {
 })
 
 
-```
-
-```mjs title=runtime.mjs
-
-
-
 ```
 
 ```mjs title=value_js.mjs

tests/rspack-test/esmOutputCases/externals/externals-import-render/__snapshots__/esm.snap.txt

@@ -16,10 +16,4 @@ it('should compile', () => {
 })
 
 
-```
-
-```mjs title=runtime.mjs
-
-
-
 ```

tests/rspack-test/esmOutputCases/re-exports/deep-re-exports-esm/__snapshots__/esm.snap.txt

@@ -24,10 +24,4 @@ it('should re-export esm correctly', async () => {
 
 export { lib2_lib2 as lib2, lib3_lib3 as lib3, lib_lib as lib };
 
-```
-
-```mjs title=runtime.mjs
-
-
-
 ```

tests/rspack-test/esmOutputCases/re-exports/re-export-external/__snapshots__/esm.snap.txt

@@ -38,10 +38,4 @@ it('should compile and import success', async () => {
 export { external_fs_readFile as r, external_fs_readFile as readFile, fs_0 as fs, named, starExports };
 export * from "fs";
 
-```
-
-```mjs title=runtime.mjs
-
-
-
 ```