fix: correctly create snapshot for rejected errors

packages/vitest/src/integrations/snapshot/chai.ts

@@ -10,15 +10,27 @@ export function getSnapshotClient(): SnapshotClient {
   return _client
 }
 
-const getErrorString = (expected: () => void) => {
+const getErrorMessage = (err: unknown) => {
+  if (err instanceof Error)
+    return err.message
+
+  return err
+}
+
+const getErrorString = (expected: () => void | Error, promise: string | undefined) => {
+  if (typeof expected !== 'function') {
+    if (!promise)
+      throw new Error(`expected must be a function, received ${typeof expected}`)
+
+    // when "promised", it receives thrown error
+    return getErrorMessage(expected)
+  }
+
   try {
     expected()
   }
   catch (e) {
-    if (e instanceof Error)
-      return e.message
-
-    return e
+    return getErrorMessage(e)
   }
 
   throw new Error('snapshot function didn\'t threw')
@@ -81,9 +93,10 @@ export const SnapshotPlugin: ChaiPlugin = (chai, utils) => {
     function (this: Record<string, unknown>, message?: string) {
       const expected = utils.flag(this, 'object')
       const test = utils.flag(this, 'vitest-test')
+      const promise = utils.flag(this, 'promise') as string | undefined
       const errorMessage = utils.flag(this, 'message')
       getSnapshotClient().assert({
-        received: getErrorString(expected),
+        received: getErrorString(expected, promise),
         test,
         message,
         errorMessage,
@@ -97,9 +110,10 @@ export const SnapshotPlugin: ChaiPlugin = (chai, utils) => {
       const expected = utils.flag(this, 'object')
       const error = utils.flag(this, 'error')
       const test = utils.flag(this, 'vitest-test')
+      const promise = utils.flag(this, 'promise') as string | undefined
       const errorMessage = utils.flag(this, 'message')
       getSnapshotClient().assert({
-        received: getErrorString(expected),
+        received: getErrorString(expected, promise),
         test,
         message,
         inlineSnapshot,

test/core/test/__snapshots__/snapshot.test.ts.snap

@@ -36,6 +36,8 @@ exports[`throwing 3`] = `
 }
 `;
 
+exports[`throwing 4`] = `"omega"`;
+
 exports[`with big array 1`] = `
 {
   "this": {

test/core/test/snapshot-inline.test.ts

@@ -59,7 +59,7 @@ test('template literal', () => {
   `)
 })
 
-test('throwing inline snapshots', () => {
+test('throwing inline snapshots', async () => {
   expect(() => {
     throw new Error('omega')
   }).toThrowErrorMatchingInlineSnapshot('"omega"')
@@ -99,6 +99,16 @@ test('throwing inline snapshots', () => {
     with
     newlines"
   `)
+
+  await expect(async () => {
+    throw new Error('omega')
+  }).rejects.toThrowErrorMatchingInlineSnapshot('"omega"')
+})
+
+test('throwing expect should be a function', async () => {
+  expect(() => {
+    expect(new Error('omega')).toThrowErrorMatchingInlineSnapshot()
+  }).toThrow(/expected must be a function/)
 })
 
 test('properties inline snapshot', () => {

test/core/test/snapshot.test.ts

@@ -30,7 +30,7 @@ test('with big string', () => {
   }).toMatchSnapshot()
 })
 
-test('throwing', () => {
+test('throwing', async () => {
   expect(() => {
     throw new Error('omega')
   }).toThrowErrorMatchingSnapshot()
@@ -44,6 +44,16 @@ test('throwing', () => {
     // eslint-disable-next-line no-throw-literal
     throw { error: 'omega' }
   }).toThrowErrorMatchingSnapshot()
+
+  await expect(async () => {
+    throw new Error('omega')
+  }).rejects.toThrowErrorMatchingSnapshot()
+})
+
+test('throwing expect should be a function', async () => {
+  expect(() => {
+    expect(new Error('omega')).toThrowErrorMatchingSnapshot()
+  }).toThrow(/expected must be a function/)
 })
 
 test('properties snapshot', () => {