"commander.opts" function gets overwritten with string "test/mocha.opts" in grunt-mocha-istanbul

[wluu]

I did file an issue against grunt-mocha-istanbul and was able to find a workaround for it: pocesar/grunt-mocha-istanbul#67

However, the purpose of this issue is to see if there's a legitimate fix on this side.

Environment:

• Node: 4.7.3
• NPM: 3.10.10
• OS: macOS Sierra 10.12.3
• Mocha: 3.2.0

Steps to reproduce:

1. Download and unzip sandbox3.zip
2. Run npm install && npm test

Observed behavior:

Running "mocha_istanbul:coverage" (mocha_istanbul) task


  commander
    1) exposes extension functions


  0 passing (9ms)
  1 failing

  1) commander exposes extension functions:
     AssertionError: expected 'test/mocha.opts' to be a function
    expected 'test/mocha.opts' to have type function
        expected 'string' to be 'function'
      at Assertion.fail (node_modules/should/cjs/should.js:258:17)
      at Assertion.Object.defineProperty.value [as Function] (node_modules/should/cjs/should.js:335:19)
      at Context.<anonymous> (commander_test.js:9:463)

Notes:

• If we run our unit test with mocha@3.2.0 as a standalone, then our assertion passes.
• If we run the above sample attachment with mocha@2.5.3, then our assertion passes.
• If we run the above sample attachment with any mocha version starting at 3.0.0 and higher, then we get the above error.
• Here is the workaround specified in "commander.opts" function gets overwritten with string "test/mocha.opts" pocesar/grunt-mocha-istanbul#67:

var program = null,
      should = require('should');

describe('commander', function () {
	before(function () {
		delete require.cache[require.resolve('commander')];
		program = require('commander');
	});

	it('exposes extension functions', function () {
		program.parse.should.be.a.Function();
		program.opts.should.be.a.Function();
	});
});

[ScottFreeCode]

•If we run the above sample attachment with mocha@2.5.3 , then our assertion passes.

Only by coincidence -- Mocha 2 has an earlier version of Commander, which results in it getting a separate instance of the package. If you use Mocha 2 but remove its copy of Commander, the issue occurs.

•If we run our unit test with mocha@3.2.0 as a standalone, then our assertion passes.

If I run node_modules/.bin/mocha commander_test.js I still get the issue, so it isn't being directly caused by any Grunt plugins. Maybe you were running global Mocha, which would also have used its own instance/copy of Commander? (Grunt, on the other hand, may be running the local Mocha even if Grunt is called globally. We haven't got around to making Mocha do that, but we really should, because it surprises a lot of people that Mocha might not do what they expect if they have a global copy installed.)

Working on digging into the issue itself...

[ScottFreeCode]

As far as I can tell, ultimately this comes down to Commander modifying the module export, which is basically a global variable in effect.

There is a Commander issue about program.opts specifically: tj/commander.js#584

However, in principle you're always going to have problems (or at least a high risk of problems) using Commander in the same process as it's already been used, since the results of the previous usage will still be on the module export. To really eliminate these sorts of issues, Commander would have to be changed such that the argument processing does not modify the module export.

[wluu]

@ScottFreeCode Correct, I was using global Mocha to run commander_test.js for the standalone scenario.

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