provider/aws: Add aws_availability_zones source

[jen20]

This pull request adds a data source with a single list, available, in the schema. The list is populated with the availability zones to which an account has access within the region for which the AWS provider is configured. The list is sorted alphabetically so should remain in a predictable order.

[stack72]

why use the time as the Id? Is it just to set something?

[jen20]

This is just the convention set by @apparentlymart. It's as good as anything else :-)

[stack72]

Looks awesome! Cannot wait to use it :) I currently use this: https://github.com/terraform-community-modules/tf_aws_availability_zones

[stack72]

@jen20 so, I'm REALLY impatient and I put this through some tests :)

data "aws_availability_zones" "zones" {}

output "azs" {
  value = "${data.aws_availability_zones.zones.available}"
}

I got the following:

Apply complete! Resources: 0 added, 0 changed, 0 destroyed.

Outputs:

azs = [
  us-west-2a
  us-west-2b
  us-west-2c
]

The only issue I currently see on this is on the destroy

data.aws_availability_zones.zones: Refreshing state...
data.aws_availability_zones.zones: Destroying...
Error applying plan:

1 error(s) occurred:

* data.aws_availability_zones.zones: unknown resource type: aws_availability_zones

[apparentlymart]

In a moment of brief forgetfulness I re-implemented this as part of #6819... so if this gets merged first I'll go back and tear that out of there.

@stack72 that issue you're seeing with "unknown resource type" is one that @jen20 saw first and I saw over the weekend too, on many different data sources. It seems like a bug in the core handling of data sources during destroy, but I didn't track it down yet.

[jen20]

I think we've decided on a "convention" of naming the list on singleton resources such as this instance. So it should read ${data.aws_availability_zones.instance}. I'll update the PR and merge this. I can't reproduce the core bug with all of @apparentlymart's patches applied, although I could reliably reproduce it previously, so I think we can consider this fixed unless we come up with a new repro (on a new issue!). I'll update this PR now to line up with the new convention.

[phinze]

Tested and it Just Works ™️ with multi-provider support:

provider "aws" {
  alias  = "east1"
  region = "us-east-1"
}

provider "aws" {
  alias  = "west2"
  region = "us-west-2"
}

data "aws_availability_zones" "east" {
  provider = "aws.east1"
}

data "aws_availability_zones" "west" {
  provider = "aws.west2"
}

output "east" {
  value = "${data.aws_availability_zones.east.instance}"
}

output "west" {
  value = "${data.aws_availability_zones.west.instance}"
}

COOL! 😍

LGTM

[ghost]

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