Update Registry to respect provider aliases

[EvanBoyle]

Description

This change makes the provider registry aware of aliases. This allows provider aliases to work properly, ensuring that resources that use aliased providers don't get replaced unnecessarily.

Fixes #3979

Checklist

• I have added tests that prove my fix is effective or that my feature works

• I have updated the CHANGELOG-PENDING file with my change

[pgavlin]

It feels like this will behave subtly differently than other aliases, and I'm not sure that's what we want.

For other resource types, an alias just means "consider this resource to have the same identity as the resource in the old state". For providers, that identity influences a couple things:

1. Which provider instance is used for a particular resource, which is managed by the provider map
2. Whether or not resources that refer to the provider will be considered as requiring replacement due to a change in their provider

I think that your changes address (1)--updating the provider map ensures that resources in the old state will treat the new provider as having the same identity as their provider if it has been aliased--but I'm not sure that it addresses (2). I think that the referenced issue requires that (2) is fixed. Can you add a test for that scenario?

[EvanBoyle]

Just tested (2) out and you are correct, altering the provider results in it getting replaced but not the resources that depend on it.

Do have any suggestions on what layer to look at for addressing (2)?

[joeduffy]

Hey @EvanBoyle I was super excited to see you working on a fix for this. Any chance it will be landing soonish?

[EvanBoyle]

Update, it looks like the incorrect behavior for (2) in my test program is due to pulumi/pulumi-terraform-bridge#244

I'll write some lifecycle tests for (2) to verify.

[EvanBoyle]

@pgavlin I've added a passing test that covers those two scenarios, would you mind taking another look?