error code should preserve after stitching (#75929)

crates/next-error-code-swc-plugin/README.md

@@ -4,7 +4,7 @@
 
 This plugin transforms Next.js source code by:
 
-- Rewriting `new Error` or `Error` to include an additional property: `Object.defineProperty(new Error(...), "__NEXT_ERROR_CODE", { value: $code, enumerable: false })`. The `enumerable: false` ensures the error code won't show up in console logs while still being accessible for telemetry.
+- Rewriting `new Error` or `Error` to include an additional property: `Object.defineProperty(new Error(...), "__NEXT_ERROR_CODE", { value: $code, enumerable: false, configurable: true })`. The `enumerable: false` ensures the error code won't show up in console logs while still being accessible for telemetry. The `configurable: true` ensures the error code can be overwritten, useful for transforming errors.
 - This enables anonymous error code reporting for user feedback while keeping the message private.
 
 ## Error Code Mapping
@@ -36,6 +36,7 @@ This plugin transforms Next.js source code by:
   - **Reason:** Pre-built artefacts simplify the build process (`pnpm build` runs without requiring `cargo`).
 
 - **Rebuild Script Example:**
+
   ```bash
   #!/usr/bin/env bash
   set -e
@@ -46,3 +47,5 @@ This plugin transforms Next.js source code by:
   mv "$NEXT_JS_ROOT/crates/next-error-code-swc-plugin/target/wasm32-wasip1/release/next_error_code_swc_plugin.wasm" "$NEXT_JS_ROOT/packages/next/"
   echo "✨ Successfully built and moved WASM plugin! 🚀"
   ```
+
+- **Testing:** Navigate to `/crates/next-error-code-swc-plugin` and run `cargo test` to test the plugin

crates/next-error-code-swc-plugin/src/lib.rs

@@ -223,6 +223,13 @@ impl VisitMut for TransformVisitor {
                                         value: false,
                                     }))),
                                 }))),
+                                PropOrSpread::Prop(Box::new(Prop::KeyValue(KeyValueProp {
+                                    key: PropName::Ident("configurable".into()),
+                                    value: Box::new(Expr::Lit(Lit::Bool(Bool {
+                                        span: new_error_expr.span,
+                                        value: true,
+                                    }))),
+                                }))),
                             ],
                         })), // { value: "$code", enumerable: false }
                     },
@@ -303,21 +310,24 @@ async function fetchUserData(userId) {
         if (!response.ok) {
             throw Object.defineProperty(new Error(`Failed to fetch user ${userId}: ${response.statusText}`), "__NEXT_ERROR_CODE", {
                 value: "E1",
-                enumerable: false
+                enumerable: false,
+                configurable: true
             });
         }
         return await response.json();
     } catch (err) {
         throw Object.defineProperty(new Error(`Request failed: ${err.message}`), "__NEXT_ERROR_CODE", {
             value: "E2",
-            enumerable: false
+            enumerable: false,
+            configurable: true
         });
     }
 }
 function test1() {
     throw Object.defineProperty(new Error("Generic error"), "__NEXT_ERROR_CODE", {
         value: "E3",
-        enumerable: false
+        enumerable: false,
+        configurable: true
     });
 }
 function test2() {
@@ -326,14 +336,16 @@ function test2() {
 function test3() {
     throw Object.defineProperty(new Error("Generic error"), "__NEXT_ERROR_CODE", {
         value: "E3",
-        enumerable: false
+        enumerable: false,
+        configurable: true
     });
 }
 function test4() {
     throw new Error();
     throw Object.defineProperty(new Error("Pattern should define hostname but found\n" + JSON.stringify(pattern)), "__NEXT_ERROR_CODE", {
         value: "E5",
-        enumerable: false
+        enumerable: false,
+        configurable: true
     });
 }
 "#

packages/next/src/client/components/errors/stitched-error.ts

@@ -1,5 +1,6 @@
 import React from 'react'
 import isError from '../../../lib/is-error'
+import { copyNextErrorCode } from '../../../lib/error-telemetry-utils'
 
 const REACT_ERROR_STACK_BOTTOM_FRAME = 'react-stack-bottom-frame'
 const REACT_ERROR_STACK_BOTTOM_FRAME_REGEX = new RegExp(
@@ -25,6 +26,7 @@ export function getReactStitchedError<T = unknown>(err: T): Error | T {
   const newError = new Error(originMessage)
   // Copy all enumerable properties, e.g. digest
   Object.assign(newError, err)
+  copyNextErrorCode(err, newError)
   newError.stack = newStack
 
   // Avoid duplicate overriding stack frames

packages/next/src/lib/error-telemetry-utils.ts

@@ -22,6 +22,21 @@ export const createDigestWithErrorCode = (
   return originalDigest
 }
 
+/**
+ * Copies the error code from one error to another by setting the __NEXT_ERROR_CODE property.
+ * This allows error codes to be preserved when wrapping or transforming errors.
+ */
+export const copyNextErrorCode = (source: unknown, target: unknown): void => {
+  const errorCode = extractNextErrorCode(source)
+  if (errorCode && typeof target === 'object' && target !== null) {
+    Object.defineProperty(target, '__NEXT_ERROR_CODE', {
+      value: errorCode,
+      enumerable: false,
+      configurable: true,
+    })
+  }
+}
+
 export const extractNextErrorCode = (error: unknown): string | undefined => {
   if (
     typeof error === 'object' &&