fix: avoid breaking ssrFixStacktrace (vitejs/vite#21269)

packages/vike/utils/getBetterError.spec.ts

@@ -272,20 +272,25 @@ describe('getBetterError', () => {
   })
 
   describe('getOriginalError', () => {
-    it('returns the original error when no chain exists', () => {
+    it('returns a clone of the original error when no chain exists', () => {
       const error = new Error('Test')
       const result = getBetterError(error, {})
 
-      expect(result.getOriginalError()).toBe(error)
+      const originalError = result.getOriginalError()
+      // getOriginalError returns a clone, not the same reference
+      expect(originalError).not.toBe(error)
+      // But it has the same message
+      expect(originalError.message).toBe(error.message)
     })
 
     it('preserves getOriginalError chain', () => {
       const firstError = new Error('First error')
       const secondError = getBetterError(firstError, { message: 'Second error' })
       const thirdError = getBetterError(secondError, { message: 'Third error' })
 
-      expect(thirdError.getOriginalError()).toBe(firstError)
-      expect(secondError.getOriginalError()).toBe(firstError)
+      // Both should return clones with the original message
+      expect(thirdError.getOriginalError().message).toBe('First error')
+      expect(secondError.getOriginalError().message).toBe('First error')
     })
 
     it('chains through multiple transformations', () => {
@@ -294,23 +299,24 @@ describe('getBetterError', () => {
       const withAppend = getBetterError(withPrepend, { message: { append: ' [2]' } })
       const withReplace = getBetterError(withAppend, { message: 'Replaced' })
 
-      expect(withReplace.getOriginalError()).toBe(original)
+      expect(withReplace.getOriginalError().message).toBe('Original')
     })
   })
 
-  describe('structuredClone behavior', () => {
-    it('only preserves message and stack from Error objects', () => {
+  describe('error mutation behavior', () => {
+    it('preserves custom properties on Error objects', () => {
       const customError = new Error('Custom error')
       customError.code = 'E_CUSTOM'
       customError.statusCode = 500
 
       const result = getBetterError(customError, {})
 
-      // structuredClone only preserves message and stack from Error objects
+      // Custom properties are preserved because we mutate the error instead of cloning
+      // (to avoid breaking Vite's ssrFixStacktrace() internal rewroteStacktraces.has(err) check)
       expect(result.message).toBe('Custom error')
       expect(result.stack).toBeDefined()
-      expect(result.code).toBeUndefined()
-      expect(result.statusCode).toBeUndefined()
+      expect(result.code).toBe('E_CUSTOM')
+      expect(result.statusCode).toBe(500)
     })
   })
 

packages/vike/utils/getBetterError.ts

@@ -9,24 +9,29 @@ export { getBetterError }
 import { isObject } from './isObject.js'
 import { assertIsNotBrowser } from './assertIsNotBrowser.js'
 import { objectAssign } from './objectAssign.js'
+import { shallowClone } from './shallowClone.js'
 assertIsNotBrowser()
 
 function getBetterError(
   err: unknown,
   modifications: { message?: string | { prepend?: string; append?: string }; stack?: string; hideStack?: true },
 ) {
+  const errOriginal = shallowClone(err)
+
   let errBetter: { message: string; stack: string; hideStack?: true }
 
   // Normalize
   if (!isObject(err)) {
-    warnMalformed(err)
+    warnMalformed(errOriginal)
     errBetter = new Error(String(err)) as Required<Error>
   } else {
-    errBetter = structuredClone(err) as any
+    // We mutate instead of structuredClone(err) to avoid breaking Vite's ssrFixStacktrace() internal rewroteStacktraces.has(err) check
+    // https://github.com/vitejs/vite/blob/dafd726032daa98d0e614f97aebe9d4dbffe2ea7/packages/vite/src/node/ssr/ssrStacktrace.ts#L95
+    errBetter = err as any
   }
   errBetter.message ??= ''
   if (!errBetter.stack) {
-    warnMalformed(err)
+    warnMalformed(errOriginal)
     errBetter.stack = new Error(errBetter.message).stack!
   }
 
@@ -48,7 +53,7 @@ function getBetterError(
       const stack = errBetter.stack.slice(messagePrevIdx + messagePrev.length)
       errBetter.stack = messageNext + stack
     } else {
-      warnMalformed(err)
+      warnMalformed(errOriginal)
     }
   } else {
     if (modsMessage?.append) {
@@ -65,12 +70,12 @@ function getBetterError(
   }
 
   // Enable users to retrieve the original error
-  objectAssign(errBetter, { getOriginalError: () => (err as any)?.getOriginalError?.() ?? err })
+  objectAssign(errBetter, { getOriginalError: () => (errOriginal as any)?.getOriginalError?.() ?? errOriginal })
 
   return errBetter
 }
 
 // TO-DO/eventually: think about whether logging this warning is a good idea
-function warnMalformed(err: unknown) {
-  console.warn('Malformed error: ', err)
+function warnMalformed(errOriginal: unknown) {
+  console.warn('Malformed error: ', errOriginal)
 }

packages/vike/utils/shallowClone.ts

@@ -0,0 +1,12 @@
+export { shallowClone }
+
+import { isObject } from './isObject.js'
+
+// - AFAICT it's the most accurate.
+// - The structuredClone() built-in isn't usable: https://www.typescriptlang.org/play/?ssl=7&ssc=1&pln=9&pc=1#code/G4QwTgBApmkLwQHZQO4QKKwPZgBQHIBhAVwGcAXLAW2mzHwEoIRTnEBPAKAh95jAB0AYywATKBAT50AfUIBVAMoAVAPIBZfN149+AiiHJlCYiQgCsABkucRiCrTCEANlmSjJECmGJCjYKFEXNyhcfgZOAHpIiAAZLABzVgADYkRxADMAS3dk2zdSLGcoAVcEgn5g92FTfAAaRyrAmvEIqJjlAAswLBRWEERHHE5vX39AptwAby9qKAAxNKFcJimAXzWGIA
+function shallowClone<Obj>(obj: Obj): Obj {
+  if (!isObject(obj)) return obj
+  const clone = Object.create(Object.getPrototypeOf(obj))
+  Object.defineProperties(clone, Object.getOwnPropertyDescriptors(obj))
+  return clone
+}