Add an option for strict deepEqual (order of properties important)

Description

The ECMAScript 6 specification defines in which order the properties of an object should be traversed (See: http://www.2ality.com/2015/10/property-traversal-order-es6.html).

Therefore, in ES6, the following ought to be false:

const result = {
  stderr: '',
  stdout: 'Hello, World!\n',
  exitCode: 0
};

const expectedResult = {
  exitCode: 0,
  stderr: '',
  stdout: 'Hello, World!\n'
};

t.deepEqual(result, expectedResult);

The current (ava@0.18.1) behaviour is that deepEqual ignores the order of properties.

I suggest that deepEqual would perform strict (order aware) deepEqual by default and ask user to sort order properties of result object if property order is not important for the test.

Relevant Links

• Related discussion on ESLint (https://github.com/eslint/eslint/issues/7714)
• Previous discussion where this suggestion has been declined on the (false) grounds that order is not important (https://github.com/avajs/ava/issues/899)

Environment

Tell us which operating system you are using, as well as which versions of Node.js, npm, and AVA. Run the following to get it quickly:

Node.js v7.5.0
darwin 16.3.0
0.18.1
4.1.2

[jfmengels]

I agree with @novemberborn and @vadimdemedes. I’m starting to understand why the order can be important, but I think this only matters in pretty rare cases. I would prefer this to be implemented in a new package.

[vadimdemedes]

I wouldn’t want t.deepEqual to check for the order of keys. As for t.keyOrder, this feels like a “nice-to-have” feature, which generally we are against from. If someone absolutely has to check for the order of keys: t.deepEqual(Object.keys(obj)).