[WIP] helper/schema: GetOkExists always returns true on updates

[radeksimko]

This was discovered when debugging hashicorp/terraform-provider-aws#3642

Please note that this PR contains just a failing test, not the actual fix at this point (hence WIP). I felt it's useful to raise it, instead of trying to describe the problem in words in an issue.

cc @appilon

[apparentlymart]

GetOkExists was implemented with the knowledge that right now it wasn't going to be 100% effective, because the underlying model here doesn't preserve enough information to give an accurate answer all of the time. (See #15723, where I'd described this problem albeit in terms of boolean values rather than integers.)

Given how close we are to switching to using the HCL2 type system for the provider protocol, I'd suggest that we pause on this for now and then think about it when we port the GetOk and GetOkExists methods over to the new underlying model, and decide what is best for each of them to do here. It will probably take some testing to figure out how much room there is for adjusting the behavior here without violating existing expectations, so knowing a specific use-case in hashicorp/terraform-provider-aws#3642 will be helpful to give us something concrete to test with.

[radeksimko]

That makes sense to me. Feel free to either close or leave open. At least we have a test case we can come back to and discuss.

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

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