feat: pretty print diffs coming from cause (#5660)

packages/utils/src/error.ts

@@ -94,7 +94,7 @@ function normalizeErrorMessage(message: string) {
   return message.replace(/__(vite_ssr_import|vi_import)_\d+__\./g, '')
 }
 
-export function processError(err: any, diffOptions?: DiffOptions) {
+export function processError(err: any, diffOptions?: DiffOptions, seen = new WeakSet()) {
   if (!err || typeof err !== 'object')
     return { message: err }
   // stack is not serialized in worker communication
@@ -121,9 +121,16 @@ export function processError(err: any, diffOptions?: DiffOptions) {
   try {
     if (typeof err.message === 'string')
       err.message = normalizeErrorMessage(err.message)
+  }
+  catch {}
 
-    if (typeof err.cause === 'object' && typeof err.cause.message === 'string')
-      err.cause.message = normalizeErrorMessage(err.cause.message)
+  // some Error implementations may not allow rewriting cause
+  // in most cases, the assignment will lead to "err.cause = err.cause"
+  try {
+    if (!seen.has(err) && typeof err.cause === 'object') {
+      seen.add(err)
+      err.cause = processError(err.cause, diffOptions, seen)
+    }
   }
   catch {}
 

test/core/test/error.test.ts

@@ -35,3 +35,28 @@ test('Can correctly process error where actual and expected contains non writabl
 
   expect(() => processError(err)).not.toThrow(TypeError)
 })
+
+test('Can correctly process error where cause is a non writable property', () => {
+  const err = new Error('My error')
+
+  Object.defineProperty(err, 'cause', {
+    value: new Error('My cause'),
+    writable: false,
+    enumerable: true,
+  })
+
+  expect(() => processError(err)).not.toThrow(TypeError)
+})
+
+test('Can correctly process error where cause leads to an infinite recursion', () => {
+  const err = new Error('My error')
+
+  Object.defineProperty(err, 'cause', {
+    value: err,
+    writable: true,
+    enumerable: true,
+    configurable: true,
+  })
+
+  expect(() => processError(err)).not.toThrow()
+})

test/core/test/jest-expect.test.ts

@@ -879,6 +879,19 @@ it('correctly prints diff', () => {
   }
 })
 
+it('correctly prints diff for the cause', () => {
+  try {
+    expect({ a: 1 }).toEqual({ a: 2 })
+    expect.unreachable()
+  }
+  catch (err) {
+    setupColors(getDefaultColors())
+    const error = processError(new Error('wrapper', { cause: err }))
+    expect(error.cause.diff).toContain('-   "a": 2')
+    expect(error.cause.diff).toContain('+   "a": 1')
+  }
+})
+
 it('correctly prints diff with asymmetric matchers', () => {
   try {
     expect({ a: 1, b: 'string' }).toEqual({