fix: add next.js 16 compatibility for string nextConfig

.changeset/slow-groups-jump.md

@@ -0,0 +1,5 @@
+---
+"@lingo.dev/_compiler": patch
+---
+
+Fix Next.js 16 compatibility by handling string nextConfig parameters to prevent TypeError during webpack property assignment

packages/compiler/src/index.spec.ts

@@ -37,3 +37,19 @@ describe("compiler integration", () => {
     expect(out.plugins[0]).toBeDefined();
   });
 });
+
+it("next() handles string nextConfig (Next.js 16 compatibility)", () => {
+  // Test the problematic case from Next.js 16 where nextConfig is a string
+  const stringConfig = 'phase-production-build' as any;
+
+  const result = compiler.next({
+    sourceRoot: "src",
+    models: "lingo.dev",
+    turbopack: { enabled: false },
+  })(stringConfig);
+
+  // Should not throw an error and should return a valid NextConfig object
+  expect(typeof result).toBe("object");
+  expect(typeof result.webpack).toBe("function");
+});
+

packages/compiler/src/index.ts

@@ -184,6 +184,9 @@ export default {
       },
     ) =>
     (nextConfig: any = {}): NextConfig => {
+      if (typeof nextConfig !== 'object' || nextConfig === null) {
+    nextConfig = {};
+  }
       const mergedParams = _.merge(
         {},
         defaultParams,