Complete fix for #8160, handle subclassed objects. Added test

[brucejo75]

@ManuelDeLeon, discovered a flaw with PR #8166 which is a fix for #8160. It did not work for sub-classes of an Array.

Changed all instances of checking the array to be seq instanceof Array || _.isArray(seq).

Passes all observe-sequence tests. Added a test that verifies this works for subclassed Arrays.

[brucejo75]

Also, I want to create another test that will verify it works for arrays created in a vm because that was the reason for the fix in the first place.

To add this test I need to add a vm-browserify as a node_module for observer_sequence_tests.js.

If someone can point me in the direction to do that, I can get it done. @abernix? @mitar?

[abernix]

I realize this sub-classing of a built-in is difficult, and it'll be ideal to remove eventually. I'm not sure if it would be sufficient for this test, but the following might be more succinct and work?

function ArraySubclass() {
  const Fp = Function.prototype;
  const inst = new (Fp.bind.apply(Array, [null].concat(Array.from(arguments))));
  inst.__proto__ = ArraySubclass.prototype;
  return inst;
}
ArraySubclass.prototype = Object.create(Array.prototype);

and then I believe the code below would be fine:

var seq = new ArraySubclass(1, 1, 2);

[brucejo75]

Thanks @abernix,

Much simpler, unfortunately, the class you provided returns true to _.isArray(seq). We need:

var seq = new ArraySubclass(1, 1, 2);

seq instanceof ArraySubclass === true
seq instanceof Array === true
_.isArray(seq) === false

I think @ManuelDeLeon took his code from the code generated by the Coffeescript extends. So it might be good to stick with it? As this will likely crop up for Coffeescript users.

Also, any thoughts on being able to test the vm issue? Can I add vm-browserify to the test?

[abernix]

Have you tried using vm directly in the tests.js? meteor-node-stubs provides vm-browserify itself.

[brucejo75]

Thanks @abernix, I just tried it.

vm is not a global
I cannot require('vm') - barfs on require
I cannot required('vm') - bars on required
I cannot Npm.required('vm') - barfs on Npm
I cannot import vm from 'vm'; - barfs on import
I cannot import {vm} from 'vm'; - barfs on import

Do you or @benjamn know how a test file can load a module? I do not see any require-like statements in the test files unless they are in node_modules installed under the .npm directory.

[brucejo75]

@abernix, @benjamn Any help?

[abernix]

After further consideration, my recommendation wouldn't have worked since meteor-node-stubs aren't available from the tool tests, though you should be able to write a similar test in your own app and have it work – assuming you have meteor-node-stubs installed.

[benjamn]

Can you declare a helper function in this file called isArray that has this implementation?

[brucejo75]

Sure thing, will implement:

function isArray(arr) { return seq instanceof Array || _.isArray(arr)}

Code changed to:

 } else if (isArray(seq)) {

[brucejo75]

• updated with @benjamn's change request.
• updated tests to include sub classed Arrays

I would still like to add a test for an array created in a vm. But I do not know how to include the vm-browserify package into the tests.

[abernix]

Despite the inability to add vm tests, from what I know about the way Array behaves in that environment, and further proven by your own testing, I'll sign off on this because the test you added should accurately catch any regression with this in the future.

I realize that's not the best answer since it fails to implement a test for the exact circumstance that caused this originally but instead tests for it "in spirit", but making the test work otherwise is currently not simple and this change is obviously important.

[brucejo75]

Unfortunate. All of the tests pass if _.isArray(arr) removed from the isArray function. It is vm that needs _.isArray(arr).

[abernix]

Just as a sanity check for what might be a change that happens in the near future: does Array.isArray work for catching the vm Array.prototype as well, in the same way as Underscore's _.isArray does right now?

(I ask because Lodash is coming to Meteor and _.isArray is a direct mapping to Array.isArray in Lodash)

[brucejo75]

Array.isArray works fine. Also, I already checked lodash's implementation against vm created arrays. So no issues with that.

[brucejo75]

I was able to trim down the vm-browserify code enough that it made a reasonable function to include in the test file. Now I have tests for a vm generated array. To Summarize:

• Made simple code change to test arrays via seq instanceof Array || _.isArray(seq). Implemented as function per @benjamn request.
• Verified that this will work if _.isArray(seq) is switched to lodash, which is Array.isArray(seq)
• Added a test for subclassed objects, reduced the ArraySubClass code size a little bit.
• Added a test for "vm generated arrays"

I ran the tests with all combinations of seq instanceof Array and _.isArray(seq) and verified the tests fail as expected.

Should be complete.

[abernix]

Thanks for taking care of this, @brucejo75! Looks good.

I made one more commit (eb45830) to fix some formatting before merging this however you didn't have a branch on your account aside from your devel branch so when I pushed to it, this PR was disassociated with it. In the future, make sure you do development work on a branch within your project and not directly on the devel branch so merging works without us having to push to your main branch.

Alternatively, I guess you could disable "Allow contributors to make changes" when opening the PR, and then we'll just do it on our own branch instead of yours. Typically though, if you have branched it wouldn't be a problem.

Thanks again!

[brucejo75]

Thanks for the tip! I was unaware of it. I will try to improve next time. Thanks!

[abernix]

This should be fixed in Meteor 1.4.3.2. You can try the latest 1.4.3.2 beta and help confirm by running:

meteor update --release 1.4.3.2-beta.0

Please report back if you encounter any problems, and thanks for taking care of this!

[brucejo75]

Verified works for my test: ArraySubclassed & VM test. @ManuelDeLeon you might want to check it for your case too.