Support provider aliases

[t0yv0]

Hello!

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Issue details

variable "another_uid" {
  default = "xxxx"
}
# Method 1: Use assume_role to operate resources in the target cen account, detail see https://registry.terraform.io/providers/aliyun/alicloud/latest/docs#assume-role
provider "alicloud" {
  region = "cn-hangzhou"
  alias  = "child_account"
  assume_role {
    role_arn = "acs:ram::${var.another_uid}:role/terraform-example-assume-role"
  }
}

# Method 2: Use the target cen account's access_key, secret_key
# provider "alicloud" {
#   region     = "cn-hangzhou"
#   access_key = "access_key"
#   secret_key = "secret_key"
#   alias      = "child_account"
# }

provider "alicloud" {
  alias = "your_account"
}
data "alicloud_account" "your_account" {
  provider = alicloud.your_account
}
data "alicloud_account" "child_account" {
  provider = alicloud.child_account
}
data "alicloud_regions" "default" {
  current = true
}

resource "alicloud_cen_instance" "example" {
  provider          = alicloud.your_account
  cen_instance_name = "tf_example"
  description       = "an example for cen"
}

resource "alicloud_vpc" "child_account" {
  provider   = alicloud.child_account
  vpc_name   = "terraform-example"
  cidr_block = "172.17.3.0/24"
}
resource "alicloud_cen_instance_grant" "child_account" {
  provider          = alicloud.child_account
  cen_id            = alicloud_cen_instance.example.id
  child_instance_id = alicloud_vpc.child_account.id
  cen_owner_id      = data.alicloud_account.your_account.id
}

resource "alicloud_cen_instance_attachment" "example" {
  provider                 = alicloud.your_account
  instance_id              = alicloud_cen_instance.example.id
  child_instance_id        = alicloud_cen_instance_grant.child_account.child_instance_id
  child_instance_type      = "VPC"
  child_instance_region_id = data.alicloud_regions.default.regions.0.id
  child_instance_owner_id  = data.alicloud_account.child_account.id
}

Converting this snippet yields:

warning: /Users/t0yv0/bugs/ci-mgmt-889/repro-comments/first-class-provider/ali_cen.tf:5,1-20: Provider alias not supported; Provider aliases are not supported, ignoring alicloud=child_account
warning: /Users/t0yv0/bugs/ci-mgmt-889/repro-comments/first-class-provider/ali_cen.tf:21,1-20: Provider alias not supported; Provider aliases are not supported, ignoring alicloud=your_account

Consider supporting.

Also as a side note, introducing the new converter removed comments here, so presumably comments are no longer supported; for this example it might be fine since comments have more TF in them that didn't get converted before. Regarding aliases, prior to the converter we had some incorrect Provider options generated but that's now gone so looks like an improvement. Thank you!

Affected area/feature