`TypeError: Cannot read properties of undefined (reading 'indexOf')` with `chai.expect(func).throws('boom!')` and `func` throws non error instance

[hi-ogawa]

Reproduction: https://stackblitz.com/edit/github-caqski-mt3prakv?file=repro.js

import * as chai from 'chai';

const func = () => {
  throw {
    body: {
      message: 'Custom error type',
    },
  };
};

chai.expect(() => func()).throws('boom!');

❯ node repro.js
TypeError: Cannot read properties of undefined (reading 'indexOf')
    at Object.compatibleMessage (file:///home/projects/github-caqski-bm1zja/node_modules/chai/index.js:102:29)
    at Proxy.assertThrows (file:///home/projects/github-caqski-bm1zja/node_modules/chai/index.js:2897:51)
    at Proxy.methodWrapper (file:///home/projects/github-caqski-bm1zja/node_modules/chai/index.js:1721:25)
    at eval (file:///home/projects/github-caqski-bm1zja/repro.js:36:19)
    at _0x49baf9 (https://githubcaqskibm1zja-23jp.w-credentialless-staticblitz.com/blitz.cf284e50.js:31:819814)
    at _0x464d1b.run (https://githubcaqskibm1zja-23jp.w-credentialless-staticblitz.com/blitz.cf284e50.js:31:820546)
    at _0x39c6d6 (https://githubcaqskibm1zja-23jp.w-credentialless-staticblitz.com/blitz.cf284e50.js:31:835720)
    at _0x3cd9a5._evaluate (https://githubcaqskibm1zja-23jp.w-credentialless-staticblitz.com/blitz.cf284e50.js:31:836069)
    at _0x3cd9a5.evaluate (https://githubcaqskibm1zja-23jp.w-credentialless-staticblitz.com/blitz.cf284e50.js:31:832499)

Node.js v20.19.1

For context, a related issue is reported on Vitest vitest-dev/vitest#4559 and I created a minimal repo here.

[43081j]

this is because check-error assumes you throw an Error or a string

i suppose we should basically do this inside compatibleMessage:

function compatibleMessage(thrown, errMatcher) {
   const comparisonString = typeof thrown === 'string' ? thrown : thrown.message;
+  // can't compare against arbitrary thrown objects
+  if (comparisonString === undefined) {
+    return false;
+  }
   if (isRegExp(errMatcher)) {
     return errMatcher.test(comparisonString);
   } else if (typeof errMatcher === 'string') {
     return comparisonString.indexOf(errMatcher) !== -1;
   }

   return false;
 }

[43081j]

have opened chaijs/check-error#66