ImmutableObject should tolerate arrays at deeper levels and prevent mutation on them — Fails in Safari

[subtleGradient]

>> not ok 382 - utils/__tests__/ImmutableObject-test ImmutableObject should tolerate arrays at deeper levels and prevent mutation on them:DEV.

https://travis-ci.org/facebook/react/jobs/14942607#L3829

http://saucelabs.com/tests/e516f61322464a97aea25b226103ce0a

[plievone]

Offending test case is here: https://github.com/facebook/react/blob/4f57515/src/utils/__tests__/ImmutableObject-test.js#L233-L252
With webdriver-jasmine:saucelabs_ios5 it fails on both DEV and PROD.
That file has quite many if (window.callPhantom) { return; } lines, which always return success locally, instead of skipping them, so it may have invalid test cases?
ImmutableObject uses Object.freeze in DEV https://github.com/facebook/react/blob/4f57515/src/utils/ImmutableObject.js#L82 without checking availability (http://kangax.github.io/es5-compat-table/#Object.freeze), and es5-sham cannot shim it.

[jordwalke]

Thanks for catching this. We need to detect if Object.freeze is supported. If not, then we shouldn't freeze. Also, the action items to support Arrays are:

1. When "merging" (shallow or deep), simply move the entire array over, do not for-in them and do not recurse. Pete had ideas to be able to specify how arrays should be intelligently merged (appended, prepended, index-by-index replace).
2. Probably something else as well.

[zpao]

We should test for Object.freeze, but we should probably actually just remove this from the repo, we don't use it. Also tests could be updated to use Object.isFrozen instead of depending on throwing (which only happens in strict mode, so IE9 which supports freezing but not strict mode fails).