[BUGFIX release] Fix cyclic references on Array.prototype

[jacobq]

My first non-doc ember.js PR so please be kind :)

• Should detect the regression that causes v3.6.0-beta.3 JQuery.extend (recursively) is broken #17190
• Test currently fails (correctly) on master but passes on v3.5.1
• Not sure if the test is located in the right place or applied to the right object(s)
• Note: this only checks the first level (e.g. won't catch a nested reference)

[jacobq]

I am looking at this again as it seems to have failed to correctly identify the point in git commit history was introduced. (It appears to pass against 246435e although that seems to be where the regression happened)

[jacobq]

@rwjblue Thanks for taking this on. Could you help me understand something here? How come when I checkout 246435e and build it, running the script below in node shows the problem, but running the test that import NativeArray passes (seems that the for...in loop iterates zero times)?

Test by loading Ember in NodeJS

Script

global.EmberENV = {
  EXTEND_PROTOTYPES: false,
};

const Ember = require('./dist/ember.debug.js');

const isOK = (a, original) => {
  original = original || a;
  for (let p in a) {
    if (a[p] === a) {
      return false;
    }
    else if (typeof a === 'object') {
      try {
        if (!isOK(a[p], a)) {
          return false;
        }
      } catch(e) {
        console.warn(`Caught exception while attempting recursive call: ${e.message}`);
        return false;
      }
    }
  }
  return true;
}

const check = (klass) => {
  const a = new klass();
  const result = isOK(a);
  console.log(`  * ${klass.name} ${result ? 'is ok' : 'is NOT OK -- cycle detected!'}`); 
}

// Extend this instead of built-in Array to avoid pollution
class ExtendedArray extends Array {}
Ember.NativeArray.apply(ExtendedArray.prototype);

// Just for fun, check nested case:
class CyclicThing {
  constructor() {
    this.sneaky = {
      firstLevelProp: 'foo',
      bar: {
        baz: 'quux',
        cycleWillBeHere: null
      }
    }
    this.sneaky.bar.cycleWillBeHere = this.sneaky;
  }
}

[Array, ExtendedArray, CyclicThing].forEach(check);

Output

  * Array is ok
  * ExtendedArray is NOT OK -- cycle detected!
Caught exception while attempting recursive call: Maximum call stack size exceeded
  * CyclicThing is NOT OK -- cycle detected!

[jacobq]

Also, FWIW, there's an is-circular module that could be used instead of my home-made function.

[rwjblue]

Just pushed a commit fixing the issue (details in the comments and commit message).