Turbopack: split up server actions modules for better treeshaking (#76877)

Closes PACK-4074

We really need to look into getting e2e tests for correct sourcemaps: PACK-4142

Fix Turbopack server action tree shaking by explicitly splitting up that module

```js
/* __next_internal_action_entry_do_not_use__ {"00c18c215a6b7cdc64bf709f3a714ffdef1bf9651d":"default","70e10665baac148856374b2789aceb970f66fec33e":"myAction"} */ import { createServerReference, callServer, findSourceMapURL } from "private-next-rsc-action-client-wrapper";
export var foo = /*#__PURE__*/ createServerReference("70e10665baac148856374b2789aceb970f66fec33e", callServer, void 0, findSourceMapURL, "myAction");
export var bar = /*#__PURE__*/ createServerReference("00c18c215a6b7cdc64bf709f3a714ffdef1bf9651d", callServer, void 0, findSourceMapURL, "default");
```
->
```js
"use turbopack no side effects";
export { foo } from "data:text/javascript,%2F%2A%20__next_internal_action_entry_do_not_use__%20%7B%2200ab21efdafbe611287bc25c0462b1e0510d13e48b%22%3A%22foo%22%7D%20%2A%2F%22use%20turbopack%20no%20side%20effects%22%3Bimport%7BcreateServerReference%2CcallServer%2CfindSourceMapURL%7Dfrom%22private-next-rsc-action-client-wrapper%22%3Bexport%20var%20foo%3D%2F%2A%23__PURE__%2A%2FcreateServerReference%28%2200ab21efdafbe611287bc25c0462b1e0510d13e48b%22%2CcallServer%2Cvoid%200%2CfindSourceMapURL%2C%22foo%22%29%3B";
export { bar } from "data:text/javascript,%2F%2A%20__next_internal_action_entry_do_not_use__%20%7B%2200ac840dcaf5e8197cb02b7f3a43c119b7a770b272%22%3A%22bar%22%7D%20%2A%2F%22use%20turbopack%20no%20side%20effects%22%3Bimport%7BcreateServerReference%2CcallServer%2CfindSourceMapURL%7Dfrom%22private-next-rsc-action-client-wrapper%22%3Bexport%20var%20bar%3D%2F%2A%23__PURE__%2A%2FcreateServerReference%28%2200ac840dcaf5e8197cb02b7f3a43c119b7a770b272%22%2CcallServer%2Cvoid%200%2CfindSourceMapURL%2C%22bar%22%29%3B";
````

- [x] Keep [sourcemaps](https://github.com/vercel/next.js/blob/canary/test/development/app-dir/source-mapping/README.md#server-actions)

Author: mischnic

Cargo.lock

@@ -1287,7 +1287,7 @@ pub async fn get_source_map_rope(
     }
 
     if map.await?.is_none() {
-        bail!("chunk/module is missing a sourcemap");
+        bail!("chunk/module '{}' is missing a sourcemap", file_path);
     }
 
     Ok(Some(map))

crates/napi/src/next_api/project.rs

@@ -225,10 +225,11 @@ impl ServerActionsGraph {
             let actions = data
                 .iter()
                 .map(|(module, (layer, actions))| async move {
+                    let actions = actions.await?;
                     actions
-                        .await?
+                        .actions
                         .iter()
-                        .map(|(hash, name)| async move {
+                        .map(async |(hash, name)| {
                             Ok((
                                 hash.to_string(),
                                 (
@@ -237,7 +238,13 @@ impl ServerActionsGraph {
                                     if *layer == ActionLayer::Rsc {
                                         *module
                                     } else {
-                                        to_rsc_context(**module, rsc_asset_context).await?
+                                        to_rsc_context(
+                                            **module,
+                                            &actions.entry_path,
+                                            &actions.entry_query,
+                                            rsc_asset_context,
+                                        )
+                                        .await?
                                     },
                                 ),
                             ))

crates/next-api/src/module_graph.rs

@@ -203,10 +203,18 @@ async fn build_manifest(
 /// The ActionBrowser layer's module is in the Client context, and we need to
 /// bring it into the RSC context.
 pub async fn to_rsc_context(
-    module: Vc<Box<dyn Module>>,
+    client_module: Vc<Box<dyn Module>>,
+    entry_path: &str,
+    entry_query: &str,
     asset_context: Vc<Box<dyn AssetContext>>,
 ) -> Result<ResolvedVc<Box<dyn Module>>> {
-    let source = FileSource::new_with_query(module.ident().path(), module.ident().query());
+    // TODO a cleaner solution would something similar to the EcmascriptClientReferenceModule, as
+    // opposed to the following hack to construct the RSC module corresponding to this client
+    // module.
+    let source = FileSource::new_with_query(
+        client_module.ident().path().root().join(entry_path.into()),
+        Vc::cell(entry_query.into()),
+    );
     let module = asset_context
         .process(
             Vc::upcast(source),
@@ -227,7 +235,7 @@ pub async fn to_rsc_context(
 pub fn parse_server_actions(
     program: &Program,
     comments: &dyn Comments,
-) -> Option<BTreeMap<String, String>> {
+) -> Option<(BTreeMap<String, String>, String, String)> {
     let byte_pos = match program {
         Program::Module(m) => m.span.lo,
         Program::Script(s) => s.span.lo,
@@ -273,7 +281,8 @@ async fn parse_actions(module: Vc<Box<dyn Module>>) -> Result<Vc<OptionActionMap
         return Ok(Vc::cell(None));
     };
 
-    let Some(mut actions) = parse_server_actions(original, comments) else {
+    let Some((mut actions, entry_path, entry_query)) = parse_server_actions(original, comments)
+    else {
         return Ok(Vc::cell(None));
     };
 
@@ -294,7 +303,14 @@ async fn parse_actions(module: Vc<Box<dyn Module>>) -> Result<Vc<OptionActionMap
 
     let mut actions = FxIndexMap::from_iter(actions.into_iter());
     actions.sort_keys();
-    Ok(Vc::cell(Some(ResolvedVc::cell(actions))))
+    Ok(Vc::cell(Some(
+        ActionMap {
+            actions,
+            entry_path,
+            entry_query,
+        }
+        .resolved_cell(),
+    )))
 }
 
 fn all_export_names(program: &Program) -> Vec<Atom> {
@@ -395,8 +411,13 @@ impl AllActions {
 }
 
 /// Maps the hashed action id to the action's exported function name.
-#[turbo_tasks::value(transparent)]
-pub struct ActionMap(FxIndexMap<String, String>);
+#[turbo_tasks::value]
+#[derive(Debug)]
+pub struct ActionMap {
+    pub actions: FxIndexMap<String, String>,
+    pub entry_path: String,
+    pub entry_query: String,
+}
 
 /// An Option wrapper around [ActionMap].
 #[turbo_tasks::value(transparent)]

crates/next-api/src/server_actions.rs

@@ -86,13 +86,16 @@ fn match_js_extension(enable_mdx_rs: bool) -> Vec<RuleCondition> {
         RuleCondition::ResourcePathEndsWith(".tsx".to_string()),
         RuleCondition::ResourcePathEndsWith(".mjs".to_string()),
         RuleCondition::ResourcePathEndsWith(".cjs".to_string()),
+        RuleCondition::ContentTypeStartsWith("application/javascript".to_string()),
+        RuleCondition::ContentTypeStartsWith("text/javascript".to_string()),
     ];
 
     if enable_mdx_rs {
         conditions.append(
             vec![
                 RuleCondition::ResourcePathEndsWith(".md".to_string()),
                 RuleCondition::ResourcePathEndsWith(".mdx".to_string()),
+                RuleCondition::ContentTypeStartsWith("text/markdown".to_string()),
             ]
             .as_mut(),
         );

crates/next-core/src/next_shared/transforms/mod.rs

@@ -1,6 +1,8 @@
 use anyhow::Result;
 use async_trait::async_trait;
-use next_custom_transforms::transforms::server_actions::{server_actions, Config};
+use next_custom_transforms::transforms::server_actions::{
+    server_actions, Config, ServerActionsMode,
+};
 use swc_core::{common::FileName, ecma::ast::Program};
 use turbo_rcstr::RcStr;
 use turbo_tasks::{ResolvedVc, Vc};
@@ -12,7 +14,9 @@ use crate::{mode::NextMode, next_config::CacheKinds};
 
 #[derive(Debug)]
 pub enum ActionsTransform {
+    /// Browser and SSR
     Client,
+    /// RSC Server
     Server,
 }
 
@@ -57,6 +61,7 @@ impl CustomTransformer for NextServerActions {
     async fn transform(&self, program: &mut Program, ctx: &TransformContext<'_>) -> Result<()> {
         let actions = server_actions(
             &FileName::Real(ctx.file_path_str.into()),
+            Some(ctx.query_str.clone()),
             Config {
                 is_react_server_layer: matches!(self.transform, ActionsTransform::Server),
                 is_development: self.mode.is_development(),
@@ -65,7 +70,9 @@ impl CustomTransformer for NextServerActions {
                 cache_kinds: self.cache_kinds.owned().await?,
             },
             ctx.comments.clone(),
+            ctx.source_map.clone(),
             Default::default(),
+            ServerActionsMode::Turbopack,
         );
         program.mutate(actions);
         Ok(())

crates/next-core/src/next_shared/transforms/server_actions.rs

@@ -14,6 +14,7 @@ plugin = [
 workspace = true
 
 [dependencies]
+base64 = "0.21.0"
 chrono = "0.4"
 easy-error = "1.0.0"
 either = "1"
@@ -38,6 +39,7 @@ swc_core = { workspace = true, features = [
   "cached",
   "common_concurrent",
   "ecma_ast",
+  "ecma_codegen",
   "ecma_loader_lru",
   "ecma_loader_node",
   "ecma_minifier",
@@ -59,6 +61,7 @@ swc_emotion = { workspace = true }
 swc_relay = { workspace = true }
 turbopack-ecmascript-plugins = { workspace = true, optional = true }
 turbo-rcstr = { workspace = true }
+urlencoding = { workspace = true }
 
 react_remove_properties = "0.33.0"
 remove_console = "0.34.0"

crates/next-custom-transforms/Cargo.toml

@@ -27,6 +27,7 @@ use crate::{
         fonts::next_font_loaders,
         lint_codemod_comments::lint_codemod_comments,
         react_server_components,
+        server_actions::ServerActionsMode,
     },
 };
 
@@ -323,9 +324,12 @@ where
             match &opts.server_actions {
                 Some(config) => Either::Left(crate::transforms::server_actions::server_actions(
                     &file.name,
+                    None,
                     config.clone(),
                     comments.clone(),
+                    cm.clone(),
                     use_cache_telemetry_tracker,
+                    ServerActionsMode::Webpack,
                 )),
                 None => Either::Right(noop_pass()),
             },