[BUGFIX canary]: Remove the last Symbols

[dcyriller]

Description

This is an attempt at removing the last Symbols from master. The goal is to fix IE compatibility regarding Symbol support, as detailed in this issue: #6380.

It won't have to be backported. Indeed, the Identifier feature has been turned on in #6366 and included in a tag for the first time in v3.14.0-alpha.2.

Thank you for pointing me to that solution @rwjblue (#6389).

Concerns

With the implementation I've done, I'm concerned by the fact:

• it kind of changes the StableIdentifier interface
• the isStableIdentifier signature is modified

But as it is still on canary, it might be fine?

Is the symbol fix good enough? It has been suggested it could be replaced by the WeakMap fix every time symbol is used.

Tests

I've run the tests with the command: yarn test. Identifier feature flag being turned on, the test seemed to be fine. I'd be happy to add more if needed.

[dcyriller]

External Partner Travis is failing in Azure, but not in Travis.

[runspired]

The existing work is good however we will want to ensure that the identifier is removed from the WeakMap when removed from the identifiers cache here https://github.com/emberjs/data/blob/master/packages/store/addon/-private/identifiers/cache.ts#L376

(We should do this because although WeakMap's allow for key GC they don't guarantee it)

[rwjblue]

Ya, if there are for sure places where we know we can remove, we totally should.

[dcyriller]

we will want to ensure that the identifier is removed from the WeakMap when removed from the identifiers cache

It's added.

Also, I've added a naive unit test for is-stable-identifier module. But I've failed on the module's import statement:

Could not find module `@ember-data/store/addon/-private/identifiers/is-stable-identifier` imported from `dummy/tests/unit/identifiers/utils/is-stable-identifier-test`

What am I missing?

[dcyriller]

Whoo tests are passing. What do you think of the added test @runspired?

[runspired]

Overall looks good, I'd like to use getOrCreateRecordIdentifier as we're testing a resource-hash with a constant ID, and add one assertion.