postgresql_role trying to revoke when it shouldn't, and failing

This issue was originally opened by @waynejnicklin as hashicorp/terraform#26257. It was migrated here as a result of the provider split. The original body of the issue is below.

---

I'm trying to add roles to the postgresql admin user that is created when the postgresql server is created in Azure.

The "plan" step looks correct:

~ roles = [
"azure_pg_admin",
+ "gfp_aiq_adm",
+ "gfp_attributemanager_adm",
+ "gfp_gfdmmanager_adm",
+ "gfp_lightspark_adm",
+ "gfp_mdmrelay_adm",
+ "gfp_rcs_adm",
"gfp_ruleservice_adm",
]
So the plan is to leave the azure_pg_admin role untouched, and the gfp_ruleservice_adm role... correctly... and to add the additional roles that I specified in the Terraform.

However, when the "apply" step is run, the following error occurs:

2020-09-16T09:14:08.6061271Z �[1m�[31mError: �[0m�[0m�[1mcould not revoke role azure_pg_admin from postgresqldev: pq: must be superuser to perform revoke role azure_pg_admin on server owner�[0m

So the issue is that the "apply" is doing something different to what the "plan" is saying. It's trying to revoke a role (and failing because it's not a superuser), but it shouldn't be trying to revoke that role as there is no change for that role in the "plan" file.

[waynejnicklin]

When will this be merged and available to use? I tried it just now and get the error:
"The provider provider.postgresql does not support resource type "postgresql_grant_role"."

Thanks,
Wayne