Only allow node runtime in proxy (#85139)

This PR is the initiative of deprecating the edge runtime. Proxy will
default to Node.js runtime, and will not allow runtime config. If the
users want to use the edge runtime, they should stay on the Middleware,
though we recommend starting the migration.

---------

Co-authored-by: devjiwonchoi <devjiwonchoi@gmail.com>
Co-authored-by: JJ Kasper <jj@jjsweb.site>

Author: 3 people

Cargo.lock

@@ -6,8 +6,7 @@ use next_core::{
     middleware::get_middleware_module,
     next_edge::entry::wrap_edge_entry,
     next_manifests::{EdgeFunctionDefinition, MiddlewaresManifestV2, ProxyMatcher, Regions},
-    parse_segment_config_from_source,
-    segment_config::ParseSegmentMode,
+    segment_config::NextSegmentConfig,
     util::{MiddlewareMatcherKind, NextRuntime},
 };
 use tracing::Instrument;
@@ -49,6 +48,8 @@ pub struct MiddlewareEndpoint {
     source: ResolvedVc<Box<dyn Source>>,
     app_dir: Option<FileSystemPath>,
     ecmascript_client_reference_transition_name: Option<RcStr>,
+    config: ResolvedVc<NextSegmentConfig>,
+    runtime: NextRuntime,
 }
 
 #[turbo_tasks::value_impl]
@@ -60,13 +61,17 @@ impl MiddlewareEndpoint {
         source: ResolvedVc<Box<dyn Source>>,
         app_dir: Option<FileSystemPath>,
         ecmascript_client_reference_transition_name: Option<RcStr>,
+        config: ResolvedVc<NextSegmentConfig>,
+        runtime: NextRuntime,
     ) -> Vc<Self> {
         Self {
             project,
             asset_context,
             source,
             app_dir,
             ecmascript_client_reference_transition_name,
+            config,
+            runtime,
         }
         .cell()
     }
@@ -81,20 +86,20 @@ impl MiddlewareEndpoint {
             )
             .module();
 
+        let userland_path = userland_module.ident().path().await?;
+        let is_proxy = userland_path.file_stem() == Some("proxy");
+
         let module = get_middleware_module(
             *self.asset_context,
             self.project.project_path().owned().await?,
             userland_module,
+            is_proxy,
         );
 
-        let runtime = parse_segment_config_from_source(*self.source, ParseSegmentMode::Base)
-            .await?
-            .runtime
-            .unwrap_or(NextRuntime::Edge);
-
-        if matches!(runtime, NextRuntime::NodeJs) {
+        if matches!(self.runtime, NextRuntime::NodeJs) {
             return Ok(module);
         }
+
         Ok(wrap_edge_entry(
             *self.asset_context,
             self.project.project_path().owned().await?,
@@ -152,10 +157,7 @@ impl MiddlewareEndpoint {
     #[turbo_tasks::function]
     async fn output_assets(self: Vc<Self>) -> Result<Vc<OutputAssets>> {
         let this = self.await?;
-
-        let config =
-            parse_segment_config_from_source(*self.await?.source, ParseSegmentMode::Base).await?;
-        let runtime = config.runtime.unwrap_or(NextRuntime::Edge);
+        let config = this.config.await?;
 
         let next_config = this.project.next_config();
         let i18n = next_config.i18n().await?;
@@ -223,7 +225,7 @@ impl MiddlewareEndpoint {
             }]
         };
 
-        if matches!(runtime, NextRuntime::NodeJs) {
+        if matches!(this.runtime, NextRuntime::NodeJs) {
             let chunk = self.node_chunk().to_resolved().await?;
             let mut output_assets = vec![chunk];
             if this.project.next_mode().await?.is_production() {

crates/next-api/src/middleware.rs

@@ -1437,28 +1437,6 @@ impl Project {
         )))
     }
 
-    #[turbo_tasks::function]
-    async fn middleware_context(self: Vc<Self>) -> Result<Vc<Box<dyn AssetContext>>> {
-        let edge_module_context = self.edge_middleware_context();
-
-        let middleware = self.find_middleware();
-        let FindContextFileResult::Found(fs_path, _) = &*middleware.await? else {
-            return Ok(edge_module_context);
-        };
-        let source = Vc::upcast(FileSource::new(fs_path.clone()));
-
-        let runtime = parse_segment_config_from_source(source, ParseSegmentMode::Base)
-            .await?
-            .runtime
-            .unwrap_or(NextRuntime::Edge);
-
-        if matches!(runtime, NextRuntime::NodeJs) {
-            Ok(self.node_middleware_context())
-        } else {
-            Ok(edge_module_context)
-        }
-    }
-
     #[turbo_tasks::function]
     async fn find_middleware(self: Vc<Self>) -> Result<Vc<FindContextFileResult>> {
         Ok(find_context_file(
@@ -1483,14 +1461,34 @@ impl Project {
             .as_ref()
             .map(|_| AppProject::client_transition_name());
 
-        let middleware_asset_context = self.middleware_context();
+        let is_proxy = fs_path.file_stem() == Some("proxy");
+        let config = parse_segment_config_from_source(
+            source,
+            if is_proxy {
+                ParseSegmentMode::Proxy
+            } else {
+                ParseSegmentMode::Base
+            },
+        );
+        let runtime = config.await?.runtime.unwrap_or(if is_proxy {
+            NextRuntime::NodeJs
+        } else {
+            NextRuntime::Edge
+        });
+
+        let middleware_asset_context = match runtime {
+            NextRuntime::NodeJs => self.node_middleware_context(),
+            NextRuntime::Edge => self.edge_middleware_context(),
+        };
 
         Ok(Vc::upcast(MiddlewareEndpoint::new(
             self,
             middleware_asset_context,
             source,
             app_dir.clone(),
             ecmascript_client_reference_transition_name,
+            config,
+            runtime,
         )))
     }
 

crates/next-api/src/project.rs

@@ -32,12 +32,12 @@ pub async fn get_middleware_module(
     asset_context: Vc<Box<dyn AssetContext>>,
     project_root: FileSystemPath,
     userland_module: ResolvedVc<Box<dyn Module>>,
+    is_proxy: bool,
 ) -> Result<Vc<Box<dyn Module>>> {
     const INNER: &str = "INNER_MIDDLEWARE_MODULE";
 
     // Determine if this is a proxy file by checking the module path
     let userland_path = userland_module.ident().path().await?;
-    let is_proxy = userland_path.file_stem() == Some("proxy");
     let (file_type, function_name, page_path) = if is_proxy {
         ("Proxy", "proxy", "/proxy")
     } else {
@@ -91,11 +91,7 @@ pub async fn get_middleware_module(
     let source = load_next_js_template(
         "middleware.js",
         project_root,
-        &[
-            ("VAR_USERLAND", INNER),
-            ("VAR_DEFINITION_PAGE", page_path),
-            ("VAR_MODULE_RELATIVE_PATH", userland_path.path.as_str()),
-        ],
+        &[("VAR_USERLAND", INNER), ("VAR_DEFINITION_PAGE", page_path)],
         &[],
         &[],
     )

crates/next-core/src/middleware.rs

@@ -289,6 +289,8 @@ pub enum ParseSegmentMode {
     Base,
     // Disallows "use client + generateStatic" and ignores/warns about `export const config`
     App,
+    // Disallows config = { runtime: "edge" }
+    Proxy,
 }
 
 /// Parse the raw source code of a file to get the segment config local to that file.
@@ -667,21 +669,35 @@ async fn parse_config_value(
                             .await;
                         };
 
-                        config.runtime =
-                            match serde_json::from_value(Value::String(val.to_string())) {
-                                Ok(runtime) => Some(runtime),
-                                Err(err) => {
-                                    return invalid_config(
-                                        source,
-                                        "config",
-                                        span,
-                                        format!("`runtime` has an invalid value: {err}.").into(),
-                                        Some(value),
-                                        IssueSeverity::Error,
-                                    )
-                                    .await;
-                                }
-                            };
+                        let runtime = match serde_json::from_value(Value::String(val.to_string())) {
+                            Ok(runtime) => Some(runtime),
+                            Err(err) => {
+                                return invalid_config(
+                                    source,
+                                    "config",
+                                    span,
+                                    format!("`runtime` has an invalid value: {err}.").into(),
+                                    Some(value),
+                                    IssueSeverity::Error,
+                                )
+                                .await;
+                            }
+                        };
+
+                        if mode == ParseSegmentMode::Proxy && runtime == Some(NextRuntime::Edge) {
+                            invalid_config(
+                                source,
+                                "config",
+                                span,
+                                rcstr!("Proxy does not support Edge runtime."),
+                                Some(value),
+                                IssueSeverity::Error,
+                            )
+                            .await?;
+                            continue;
+                        }
+
+                        config.runtime = runtime
                     }
                     "matcher" => {
                         config.middleware_matcher =

crates/next-core/src/segment_config.rs

@@ -901,5 +901,6 @@
   "900": "Both %s file \"./%s\" and %s file \"./%s\" are detected. Please use \"./%s\" only. Learn more: https://nextjs.org/docs/messages/middleware-to-proxy",
   "901": "Invalid \"cacheHandlers\" provided, expected an object e.g. { default: '/my-handler.js' }, received %s",
   "902": "Invalid handler fields configured for \"cacheHandlers\":\\n%s",
-  "903": "The file \"%s\" must export a function, either as a default export or as a named \"%s\" export.\\nThis function is what Next.js runs for every request handled by this %s.\\n\\nWhy this happens:\\n%s- The file exists but doesn't export a function.\\n- The export is not a function (e.g., an object or constant).\\n- There's a syntax error preventing the export from being recognized.\\n\\nTo fix it:\\n- Ensure this file has either a default or \"%s\" function export.\\n\\nLearn more: https://nextjs.org/docs/messages/middleware-to-proxy"
+  "903": "The file \"%s\" must export a function, either as a default export or as a named \"%s\" export.\\nThis function is what Next.js runs for every request handled by this %s.\\n\\nWhy this happens:\\n%s- The file exists but doesn't export a function.\\n- The export is not a function (e.g., an object or constant).\\n- There's a syntax error preventing the export from being recognized.\\n\\nTo fix it:\\n- Ensure this file has either a default or \"%s\" function export.\\n\\nLearn more: https://nextjs.org/docs/messages/middleware-to-proxy",
+  "904": "The file \"%s\" must export a function, either as a default export or as a named \"%s\" export."
 }