Fix Next 16.1 not including skipTrailingSlashRedirect

.changeset/whole-bats-sip.md

@@ -0,0 +1,5 @@
+---
+"@opennextjs/aws": patch
+---
+
+Fix for Next 16.1 config

packages/open-next/src/build/copyTracedFiles.ts

@@ -303,12 +303,13 @@ File ${serverPath} does not exist
       (fileOrDir) =>
         !statSync(path.join(standaloneNextDir, fileOrDir)).isDirectory(),
     )
-    .forEach((file) =>
+    .forEach((file) => {
       copyFileSync(
         path.join(standaloneNextDir, file),
         path.join(outputNextDir, file),
-      ),
-    );
+      );
+      tracedFiles.push(path.join(outputNextDir, file));
+    });
 
   // We then need to copy all the files at the root of server
 
@@ -320,12 +321,13 @@ File ${serverPath} does not exist
         !statSync(path.join(standaloneServerDir, fileOrDir)).isDirectory(),
     )
     .filter((file) => file !== "server.js")
-    .forEach((file) =>
+    .forEach((file) => {
       copyFileSync(
         path.join(standaloneServerDir, file),
         path.join(path.join(outputNextDir, "server"), file),
-      ),
-    );
+      );
+      tracedFiles.push(path.join(outputNextDir, "server", file));
+    });
 
   // Copy patch file
   copyPatchFile(path.join(outputDir, packagePath));

packages/open-next/src/build/createServerBundle.ts

@@ -207,6 +207,7 @@ async function generateBundle(
     patches.patchBackgroundRevalidation,
     patches.patchUseCacheForISR,
     patches.patchNodeEnvironment,
+    patches.patchNextConfig,
     ...additionalCodePatches,
   ]);
 

packages/open-next/src/build/patch/codePatcher.ts

@@ -33,6 +33,10 @@ export type PatchCodeFn = (args: {
    * Next.js manifests that are used by Next at runtime
    */
   manifests: ReturnType<typeof getManifests>;
+  /**
+   * OpenNext build options
+   */
+  buildOptions: buildHelper.BuildOptions;
 }) => Promise<string>;
 
 interface IndividualPatch {
@@ -168,6 +172,7 @@ export async function applyCodePatches(
           filePath,
           tracedFiles,
           manifests,
+          buildOptions,
         });
       }
       await fs.writeFile(filePath, patchedContent);

packages/open-next/src/build/patch/patches/index.ts

@@ -8,3 +8,4 @@ export {
 export { patchFetchCacheSetMissingWaitUntil } from "./patchFetchCacheWaitUntil.js";
 export { patchBackgroundRevalidation } from "./patchBackgroundRevalidation.js";
 export { patchNodeEnvironment } from "./patchNodeEnvironment.js";
+export { patchNextConfig } from "./patchNextConfig.js";

packages/open-next/src/build/patch/patches/patchNextConfig.ts

@@ -0,0 +1,62 @@
+import fs from "node:fs";
+import path from "node:path";
+import { buildSync } from "esbuild";
+import type { CodePatcher } from "../codePatcher";
+
+export const patchNextConfig: CodePatcher = {
+  name: "patch-next-config",
+  patches: [
+    {
+      pathFilter: /required\-server\-files\.json$/,
+      versions: ">=16.1.0",
+      patchCode: async ({ code, buildOptions }) => {
+        // Find the next.config file with any supported extension
+        const possibleExtensions = [".ts", ".mjs", ".js", ".cjs"];
+        let configPath: string | undefined;
+        let configExtension: string | undefined;
+
+        for (const ext of possibleExtensions) {
+          const testPath = path.join(buildOptions.appPath, `next.config${ext}`);
+          if (fs.existsSync(testPath)) {
+            configPath = testPath;
+            configExtension = ext;
+            break;
+          }
+        }
+
+        if (!configPath || !configExtension) {
+          throw new Error("Could not find next.config file");
+        }
+
+        let configToImport: string;
+
+        // Only compile if the extension is .ts
+        if (configExtension === ".ts") {
+          buildSync({
+            entryPoints: [configPath],
+            outfile: path.join(buildOptions.tempBuildDir, "next.config.mjs"),
+            bundle: true,
+            format: "esm",
+            platform: "node",
+          });
+          configToImport = path.join(
+            buildOptions.tempBuildDir,
+            "next.config.mjs",
+          );
+        } else {
+          // For .js, .mjs, .cjs, use the file directly
+          configToImport = configPath;
+        }
+
+        // In next 16.1+ we need to add `skipTrailingSlashRedirect` manually because next removes it from the config
+        const originalConfig = (await import(configToImport)).default;
+        const config = JSON.parse(code);
+        if (config.config.skipTrailingSlashRedirect === undefined) {
+          config.config.skipTrailingSlashRedirect =
+            originalConfig.skipTrailingSlashRedirect ?? false;
+        }
+        return JSON.stringify(config, null, 2);
+      },
+    },
+  ],
+};