JSON reporter doesn't work (no output)

[sakovias]

The issue occur to me on mocha v3.0.2 and node v5.8.0 on Mac OS X. Here's my test file

'use strict';
var app = require('./app');

describe('Converting strings.', function() {

  it('Can convert a string with one space', function() {
    var result = app.convertString('hello world');
    result.should.eql('hello-world');
  });

  it('Replaces two spaces with one dash', function() {
    app.convertString('hello  world').should.eql('hello-world');
  });
});

and the code I'm testing

function convertString(str) {
  return str.split(' ').join('-');
}

module.exports = {
  convertString: convertString
};

With json-stream reporter everything works fine:

$ mocha --require should --reporter json-stream test.js
["start",{"total":2}]
["pass",{"title":"Can convert a string with one space","fullTitle":"Converting strings. Can convert a string with one space","duration":2,"currentRetry":0}]
["fail",{"title":"Replaces two spaces with one dash","fullTitle":"Converting strings. Replaces two spaces with one dash","duration":0,"currentRetry":0,"err":"expected 'hello--world' to equal 'hello-world'","stack":"AssertionError: expected 'hello--world' to equal 'hello-world'\n    at Assertion.fail (node_modules/should/cjs/should.js:205:17)\n    at Assertion.Object.defineProperty.value (node_modules/should/cjs/should.js:277:19)\n    at Context.<anonymous> (test.js:12:46)"}]
["end",{"suites":1,"tests":2,"passes":1,"pending":0,"failures":1,"start":"2016-08-12T15:34:45.144Z","end":"2016-08-12T15:34:45.155Z","duration":11}]

but with the json reporter nothing comes out:

$ mocha --require should --reporter json test.js  # No output!

Am I doing something wrong?

[gurdiga]

It looks like should.js has a circular reference in its assertion object, and this gets Mocha’s json reporter in trouble when it tries to serialize it. 😶

Mocha (by default) catches and collects the uncaught exceptions, but at the time when this one is thrown, the reporter’s output is already prepared, and so this particular error is lost. 😑

One way to fix this is I guess to watch and cut the circular references in the json reporter. Maybe there are better ways, I’m open to advice. 🤓

[sakovias]

Good catch! Thank you for your work @gurdiga. I don't see a reason not to merge you fix 😄

That's exactly what I was noticing on my Linux distro (with slightly older mocha and node) where JSON reporter was blowing up on circular references. With newer mocha and node on Mac OS, the reporter was just going silent.

As a workaround on old Mocha folks can use json-stream reporter. It doesn't have this issue for some reason.

[boneskull]

The ./lib/utils module has a method jsonStringify() which is circular-reference safe. Would accept PR to JSON reporter to use it.

[boneskull]

as noted in #2559, I was wrong about the function (my bad)