Only allow node runtime in proxy

crates/next-api/src/middleware.rs

@@ -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/project.rs

@@ -153,7 +153,7 @@
     /// E.g. `/home/user/projects/my-repo`.
     pub root_path: RcStr,
 
     /// A path which contains the app/pages directories, relative to [`Project::root_path`], always
     /// Unix path. E.g. `apps/my-app`
     pub project_path: RcStr,
 
@@ -1437,28 +1437,6 @@
         )))
     }
 
-    #[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 @@
             .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-core/src/middleware.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/segment_config.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 =

packages/next/errors.json

@@ -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."
 }