Turbopack: Implement Server Actions (#53890)

### What?

This implements Server Actions inside the new Turbopack next-api bundles.

### How?

Server Actions requires:
1. A `.next/server/server-reference-manifest.json` manifest describing what loader module to import to invoke a server action
2. A "loader" entry point that then imports server actions from our internal chunk items
3. Importing the bundled `react-experimental` module instead of regular `react`
4. A little 🪄 pixie dust
5. A small change in the magic comment generated in modules that export server actions

I had to change the magic `__next_internal_action_entry_do_not_use__` comment generated by the server actions transformer. When I traverse the module graph to find all exported actions _after chunking_ has been performed, we no longer have access to the original file name needed to generate the server action's id hash. Adding the filename to comment allows me to recover this without overcomplicating our output pipeline.

Closes WEB-1279
Depends on vercel/turborepo#5705

Co-authored-by: Tim Neutkens <6324199+timneutkens@users.noreply.github.com>
Co-authored-by: Jiachi Liu <4800338+huozhi@users.noreply.github.com>

Cargo.toml

@@ -27,6 +27,7 @@ opt-level = 3
 next-api = { path = "packages/next-swc/crates/next-api", default-features = false }
 next-build = { path = "packages/next-swc/crates/next-build", default-features = false }
 next-core = { path = "packages/next-swc/crates/next-core", default-features = false }
+next-swc = { path = "packages/next-swc/crates/core" }
 next-transform-font = { path = "packages/next-swc/crates/next-transform-font" }
 next-transform-dynamic = { path = "packages/next-swc/crates/next-transform-dynamic" }
 next-transform-strip-page-exports = { path = "packages/next-swc/crates/next-transform-strip-page-exports" }

packages/next-swc/crates/core/src/server_actions.rs

@@ -1,4 +1,7 @@
-use std::convert::{TryFrom, TryInto};
+use std::{
+    collections::HashMap,
+    convert::{TryFrom, TryInto},
+};
 
 use hex::encode as hex_encode;
 use serde::Deserialize;
@@ -25,6 +28,9 @@ pub struct Config {
     pub enabled: bool,
 }
 
+/// A mapping of hashed action id to the action's exported function name.
+pub type ActionsMap = HashMap<String, String>;
+
 pub fn server_actions<C: Comments>(
     file_name: &FileName,
     config: Config,
@@ -33,7 +39,7 @@ pub fn server_actions<C: Comments>(
     as_folder(ServerActions {
         config,
         comments,
-        file_name: file_name.clone(),
+        file_name: file_name.to_string(),
         start_pos: BytePos(0),
         in_action_file: false,
         in_export_decl: false,
@@ -55,10 +61,40 @@ pub fn server_actions<C: Comments>(
     })
 }
 
+/// Parses the Server Actions comment for all exported action function names.
+///
+/// Action names are stored in a leading BlockComment prefixed by
+/// `__next_internal_action_entry_do_not_use__`.
+pub fn parse_server_actions<C: Comments>(program: &Program, comments: C) -> Option<ActionsMap> {
+    let byte_pos = match program {
+        Program::Module(m) => m.span.lo,
+        Program::Script(s) => s.span.lo,
+    };
+    comments.get_leading(byte_pos).and_then(|comments| {
+        comments.iter().find_map(|c| {
+            c.text
+                .split_once("__next_internal_action_entry_do_not_use__")
+                .and_then(|(_, actions)| match serde_json::from_str(actions) {
+                    Ok(v) => Some(v),
+                    Err(_) => None,
+                })
+        })
+    })
+}
+
+/// Serializes the Server Actions into a magic comment prefixed by
+/// `__next_internal_action_entry_do_not_use__`.
+fn generate_server_actions_comment(actions: ActionsMap) -> String {
+    format!(
+        " __next_internal_action_entry_do_not_use__ {} ",
+        serde_json::to_string(&actions).unwrap()
+    )
+}
+
 struct ServerActions<C: Comments> {
     #[allow(unused)]
     config: Config,
-    file_name: FileName,
+    file_name: String,
     comments: C,
 
     start_pos: BytePos,
@@ -216,7 +252,7 @@ impl<C: Comments> ServerActions<C> {
                     .cloned()
                     .map(|id| Some(id.as_arg()))
                     .collect(),
-                self.file_name.to_string(),
+                &self.file_name,
                 export_name.to_string(),
                 Some(action_ident.clone()),
             );
@@ -317,7 +353,7 @@ impl<C: Comments> ServerActions<C> {
                     .cloned()
                     .map(|id| Some(id.as_arg()))
                     .collect(),
-                self.file_name.to_string(),
+                &self.file_name,
                 export_name.to_string(),
                 Some(action_ident.clone()),
             );
@@ -923,8 +959,7 @@ impl<C: Comments> VisitMut for ServerActions<C> {
                 let ident = Ident::new(id.0.clone(), DUMMY_SP.with_ctxt(id.1));
 
                 if !self.config.is_server {
-                    let action_id =
-                        generate_action_id(self.file_name.to_string(), export_name.to_string());
+                    let action_id = generate_action_id(&self.file_name, export_name);
 
                     if export_name == "default" {
                         let export_expr = ModuleItem::ModuleDecl(ModuleDecl::ExportDefaultExpr(
@@ -973,7 +1008,7 @@ impl<C: Comments> VisitMut for ServerActions<C> {
                         &mut self.annotations,
                         ident.clone(),
                         Vec::new(),
-                        self.file_name.to_string(),
+                        &self.file_name,
                         export_name.to_string(),
                         None,
                     );
@@ -1037,26 +1072,22 @@ impl<C: Comments> VisitMut for ServerActions<C> {
         }
 
         if self.has_action {
+            let actions = if self.in_action_file {
+                self.exported_idents.iter().map(|e| e.1.clone()).collect()
+            } else {
+                self.export_actions.clone()
+            };
+            let actions = actions
+                .into_iter()
+                .map(|name| (generate_action_id(&self.file_name, &name), name))
+                .collect::<ActionsMap>();
             // Prepend a special comment to the top of the file.
             self.comments.add_leading(
                 self.start_pos,
                 Comment {
                     span: DUMMY_SP,
                     kind: CommentKind::Block,
-                    // Append a list of exported actions.
-                    text: format!(
-                        " __next_internal_action_entry_do_not_use__ {} ",
-                        if self.in_action_file {
-                            self.exported_idents
-                                .iter()
-                                .map(|e| e.1.to_string())
-                                .collect::<Vec<_>>()
-                                .join(",")
-                        } else {
-                            self.export_actions.join(",")
-                        }
-                    )
-                    .into(),
+                    text: generate_server_actions_comment(actions).into(),
                 },
             );
 
@@ -1162,7 +1193,7 @@ fn collect_pat_idents(pat: &Pat, closure_idents: &mut Vec<Id>) {
     }
 }
 
-fn generate_action_id(file_name: String, export_name: String) -> String {
+fn generate_action_id(file_name: &str, export_name: &str) -> String {
     // Attach a checksum to the action using sha1:
     // $$id = sha1('file_name' + ':' + 'export_name');
     let mut hasher = Sha1::new();
@@ -1178,7 +1209,7 @@ fn annotate_ident_as_action(
     annotations: &mut Vec<Stmt>,
     ident: Ident,
     bound: Vec<Option<ExprOrSpread>>,
-    file_name: String,
+    file_name: &str,
     export_name: String,
     maybe_orig_action_ident: Option<Ident>,
 ) {
@@ -1188,7 +1219,7 @@ fn annotate_ident_as_action(
         // $$id
         ExprOrSpread {
             spread: None,
-            expr: Box::new(generate_action_id(file_name, export_name).into()),
+            expr: Box::new(generate_action_id(file_name, &export_name).into()),
         },
         // myAction.$$bound = [arg1, arg2, arg3];
         // or myAction.$$bound = null; if there are no bound values.

packages/next-swc/crates/napi/Cargo.toml

@@ -13,7 +13,13 @@ default = ["rustls-tls"]
 # when build (i.e napi --build --features plugin), same for the wasm as well.
 # this is due to some of transitive dependencies have features cannot be enabled at the same time
 # (i.e wasmer/default vs wasmer/js-default) while cargo merges all the features at once.
-plugin = ["turbopack-binding/__swc_core_binding_napi_plugin", "turbopack-binding/__swc_core_binding_napi_plugin_filesystem_cache", "turbopack-binding/__swc_core_binding_napi_plugin_shared_runtime",  "next-swc/plugin", "next-core/plugin"]
+plugin = [
+  "turbopack-binding/__swc_core_binding_napi_plugin",
+  "turbopack-binding/__swc_core_binding_napi_plugin_filesystem_cache",
+  "turbopack-binding/__swc_core_binding_napi_plugin_shared_runtime",
+  "next-swc/plugin",
+  "next-core/plugin",
+]
 sentry_native_tls = ["sentry", "sentry/native-tls", "native-tls"]
 sentry_rustls = ["sentry", "sentry/rustls", "rustls-tls"]
 
@@ -24,9 +30,7 @@ image-avif = ["next-core/image-avif"]
 # Enable all the available image codec support.
 # Currently this is identical to `image-webp`, as we are not able to build
 # other codecs easily yet.
-image-extended = [
-  "image-webp",
-]
+image-extended = ["image-webp"]
 
 # Enable dhat profiling allocator for heap profiling.
 __internal_dhat-heap = ["dhat"]
@@ -47,7 +51,7 @@ napi = { version = "2", default-features = false, features = [
   "error_anyhow",
 ] }
 napi-derive = "2"
-next-swc = { version = "0.0.0", path = "../core" }
+next-swc = { workspace = true }
 next-api = { workspace = true }
 next-build = { workspace = true }
 next-core = { workspace = true }
@@ -73,9 +77,7 @@ turbopack-binding = { workspace = true, features = [
 ] }
 
 [target.'cfg(not(all(target_os = "linux", target_env = "musl", target_arch = "aarch64")))'.dependencies]
-turbopack-binding = { workspace = true, features = [
-  "__turbo_tasks_malloc"
-] }
+turbopack-binding = { workspace = true, features = ["__turbo_tasks_malloc"] }
 
 # There are few build targets we can't use native-tls which default features rely on,
 # allow to specify alternative (rustls) instead via features.
@@ -94,6 +96,4 @@ serde = "1"
 serde_json = "1"
 # It is not a mistake this dependency is specified in dep / build-dep both.
 shadow-rs = { workspace = true }
-turbopack-binding = { workspace = true, features = [
-  "__turbo_tasks_build"
-]}
+turbopack-binding = { workspace = true, features = ["__turbo_tasks_build"] }

packages/next-swc/crates/next-api/Cargo.toml

@@ -11,12 +11,17 @@ bench = false
 
 [features]
 default = ["custom_allocator"]
-custom_allocator = ["turbopack-binding/__turbo_tasks_malloc", "turbopack-binding/__turbo_tasks_malloc_custom_allocator"]
+custom_allocator = [
+  "turbopack-binding/__turbo_tasks_malloc",
+  "turbopack-binding/__turbo_tasks_malloc_custom_allocator",
+]
 
 [dependencies]
 anyhow = { workspace = true, features = ["backtrace"] }
 futures = { workspace = true }
+next-swc = { workspace = true }
 indexmap = { workspace = true }
+indoc = { workspace = true }
 next-core = { workspace = true }
 once_cell = { workspace = true }
 serde = { workspace = true }
@@ -35,14 +40,12 @@ turbopack-binding = { workspace = true, features = [
   "__turbopack_cli_utils",
   "__turbopack_node",
   "__turbopack_dev_server",
-]}
+] }
 turbo-tasks = { workspace = true }
 tracing = { workspace = true }
 tracing-subscriber = { workspace = true, features = ["env-filter", "json"] }
 
 [build-dependencies]
 # It is not a mistake this dependency is specified in dep / build-dep both.
 shadow-rs = { workspace = true }
-turbopack-binding = { workspace = true, features = [
-  "__turbo_tasks_build"
-]}
+turbopack-binding = { workspace = true, features = ["__turbo_tasks_build"] }

packages/next-swc/crates/next-api/src/app.rs

@@ -54,6 +54,7 @@ use turbopack_binding::{
 use crate::{
     project::Project,
     route::{Endpoint, Route, Routes, WrittenEndpoint},
+    server_actions::create_server_actions_manifest,
     server_paths::all_server_paths,
 };
 
@@ -685,6 +686,26 @@ impl AppEndpoint {
                     bail!("Entry module must be evaluatable");
                 };
                 evaluatable_assets.push(evaluatable);
+
+                let (loader, manifest) = create_server_actions_manifest(
+                    app_entry.rsc_entry,
+                    node_root,
+                    &app_entry.pathname,
+                    &app_entry.original_name,
+                    NextRuntime::Edge,
+                    Vc::upcast(this.app_project.edge_rsc_module_context()),
+                    Vc::upcast(chunking_context),
+                    this.app_project
+                        .project()
+                        .next_config()
+                        .enable_server_actions(),
+                )
+                .await?;
+                server_assets.push(manifest);
+                if let Some(loader) = loader {
+                    evaluatable_assets.push(loader);
+                }
+
                 let files = chunking_context.evaluated_chunk_group(
                     app_entry
                         .rsc_entry
@@ -783,6 +804,28 @@ impl AppEndpoint {
                 }
             }
             NextRuntime::NodeJs => {
+                let mut evaluatable_assets =
+                    this.app_project.rsc_runtime_entries().await?.clone_value();
+
+                let (loader, manifest) = create_server_actions_manifest(
+                    app_entry.rsc_entry,
+                    node_root,
+                    &app_entry.pathname,
+                    &app_entry.original_name,
+                    NextRuntime::NodeJs,
+                    Vc::upcast(this.app_project.rsc_module_context()),
+                    Vc::upcast(this.app_project.project().rsc_chunking_context()),
+                    this.app_project
+                        .project()
+                        .next_config()
+                        .enable_server_actions(),
+                )
+                .await?;
+                server_assets.push(manifest);
+                if let Some(loader) = loader {
+                    evaluatable_assets.push(loader);
+                }
+
                 let rsc_chunk = this
                     .app_project
                     .project()
@@ -793,7 +836,7 @@ impl AppEndpoint {
                             original_name = app_entry.original_name
                         )),
                         app_entry.rsc_entry,
-                        this.app_project.rsc_runtime_entries(),
+                        Vc::cell(evaluatable_assets),
                     );
                 server_assets.push(rsc_chunk);
 
@@ -816,8 +859,10 @@ impl AppEndpoint {
                     client_assets: Vc::cell(client_assets),
                 }
             }
-        };
-        Ok(endpoint_output.cell())
+        }
+        .cell();
+
+        Ok(endpoint_output)
     }
 }
 

packages/next-swc/crates/next-api/src/lib.rs

@@ -8,6 +8,7 @@ mod middleware;
 mod pages;
 pub mod project;
 pub mod route;
+mod server_actions;
 pub mod server_paths;
 mod versioned_content_map;
 

packages/next-swc/crates/next-api/src/project.rs

@@ -476,6 +476,7 @@ impl Project {
             self.env(),
             self.server_addr(),
             this.define_env.nodejs(),
+            self.next_config(),
         ))
     }