Allow data resource that lookup sets of items to return empty sets.

[bcsgh]

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Description

data resource that exist to generate a list of items should (or should be able to) return an empty list when no resource match the filters used.

New or Affected Resource(s)

More or less any data resource ending in a plural, a few of many that likely exhibit this issue:

• aws_autoscaling_groups
• aws_instances
• aws_subnet_ids
• ...

Potential Terraform Configuration

I need to create a resource for_each of some other thing. Things that exists outside TF's control.

data "aws_things" "lookup" {
  ...
}

resource "aws_other_thing" "make" {
  for_each = data.aws_things.lookup.ids

  ...
  build_from_thing = each.key
}

(note this is only one of several patterns that run into this problem, but in my experience the most common.)

Right now this works, but only when something is actually found.
When the possibility exist that in, non error condition, there may be zero of those things, making things work is much more complex.
All (or most) data resource that lookup sets of things issue an error when they find nothing.

Attempted Solutions

The general workaround is to use a wider query that is assured to always return something and lookup enough about each of those results to manually filter that in terraform.
Besides being much more complex and requiring many more data requests, this has many other issues that I shouldn't need to go into.

References

hashicorp/terraform#27712

[ewbankkit]

Related:

• docs/contributing: Add Data Sources section to Provider Design page #17546
• Feature Request: Allow data sources searching tags/filters to return empty results #8302
• Fix data source aws_vpc_peering_connections #17382
• Data source aws_vpcs should not fail if no VPCs are found #13951
• [READY] fix: vpcs datasource returns empty list when no vpcs #13982
• Feature Request: Allow data source aws_ec2_spot_price to return empty results #17446

(and probably others).

[bcsgh]

Glad to see that. It looks like other more specific issues predate this one. I'll leave it up to you to decide if having a totally general issues open is worth while. If not I'm find with this being marked as a duplicate.

Keep up the good work!

p.s. could someone please acknowledge hashicorp/terraform#13022 ?

[bflad]

We have now documented in our Provider Design documentation that plural data sources should return zero, one, or multiple results without error. Singular data sources should still return an error when the remote component is not found.

We can go back through any non-conformant plural data sources to fix them up, but this might want to wait until our next major release since it is a behavior change for the existing cases. I'm going to mark it with that milestone for tracking for now, but it might be done sooner depending on some further investigation work to determine if it was previously possible to rely on the error in configurations (e.g. with try()).

p.s. could someone please acknowledge hashicorp/terraform#13022 ?

The maintainers for this project are separate. We cannot influence any prioritization efforts upstream. The product manager for Terraform CLI is fairly open to meeting with folks to discuss things, so that is a potential option there.

[zpriddy]

I was wondering if there are any updates on this or #13951 ?

[anGie44]

List of Affected Data Sources:

• aws_vpc_peering_connections (Fix data source aws_vpc_peering_connections #17382)
• aws_cognito_user_pools
• aws_ec2_coip_pools
• aws_ebs_volumes
• aws_ec2_local_gateway_route_tables
• aws_ec2_local_gateway_virtual_interface_groups
• aws_ec2_local_gateways
• aws_instances
• aws_network_acls
• aws_network_interfaces
• aws_route_tables
• aws_security_groups
• aws_subnet_ids Deprecated in v4.0.0: d/aws_subnet_ids: Deprecate #22743
• aws_ec2_transit_gateway_route_tables
• aws_vpcs (Data source aws_vpcs should not fail if no VPCs are found #13951)
• aws_efs_access_points
• aws_emr_release_labels
• aws_inspector_rules_packages
• aws_ip_ranges
• aws_db_event_categories
• aws_ssoadmin_instances

[github-actions]

This functionality has been released in v4.0.0 of the Terraform AWS Provider. Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading.

For further feature requests or bug reports with this functionality, please create a new GitHub issue following the template. Thank you!

[github-actions]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.
If you have found a problem that seems similar to this, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.