a large refactor to addrs.AbsProviderConfig, embedding the addrs.Provider instead of a Type string. I've added and updated tests, added some Legacy functions to support older state formats and shims, and added a normalization step when reading v4 (current) state files (not the added tests under states/statefile/roundtrip which work with both current and legacy-style AbsProviderConfig strings).
The remaining 'fixme' and 'todo' comments are mostly going to be addressed in a subsequent PR and involve looking up a given local provider config's FQN. This is fine for now as we are only working with default assumption.
The state refactoring command "terraform state mv" in Terraform 0.11 does
not update existing dependency addresses recorded in the state when it
moves objects around, and Terraform only updates the dependency addresses
in the state when it performs a full update on a resource instance, and
so it's a common problem for folks updating from Terraform 0.11 with
resource names that are not valid identifiers to run into state upgrade
errors even though they have followed the instructions produced by
"terraform 0.12checklist".
Dependencies are synced from config during every refresh walk anyway, so
in practice we can get away with just discarding invalid dependency
addresses and letting the refresh walk update them. In practice these
addresses are unlikely to be pointing at a resource that actually exists
anyway, because if so Terraform 0.12's configuration parser wouldn't be
able to interpret it.
Discarding invalid dependency addresses allows the state upgrade to
complete successfully in such cases and thus gives the refresh step an
opportunity to repair the problem.
Kristin Laemmert