Diff doesn't be displayed when object has Symbol value

[ryym]

When I assert an object that has a Symbol value, the test doesn't display diff even if it fails. For example, the following test fails without generating diff.

// test.js
const assert = require('assert');

it('should generate diff', () => {
  const obj = { type: Symbol('foo') };
  assert.deepEqual(obj, { type: null });
});

result:

Then I found the stringify function in lib/utils throws a following error when the argument object has a Symbol value.

TypeError: Cannot convert a Symbol value to a string

environment:

• mocha: v2.4.5
• node: v4.2.2

[glenjamin]

I just ran into this, the json-stream and tap reports seem to hand this ok, so it's definitely a reporter problem - although the lack of an error is slightly more worrying

[ryym]

It seems the reporters like dot and spec which use this function cause this problem. The function generates diff by util.stringify() to convert Symbol to string and throws the error.
I sent PR for this issue :)

[glenjamin]

Good stuff, is it possible to fix the black-holed error too?

[ryym]

is it possible to fix the black-holed error too?

Hmm, I don't know how to fix this. My PR just adds handling of Symbol values, so it does nothing about the black-holed error. But as you say, it should be fixed too.

[glenjamin]

I've created a draft PR which attempts to solve the swallowed-error problem: #2096

[ryym]

Great!