d/aws_subnet: use Tags field from DescribeSubnets response

[jar-b]

Description

This change modifies the transparent tagging configuration for this data source to use the Tags field from the DescribeSubnets response, rather than making an additional call to the DescribeTags API. As a side effect, this data source will no longer require the calling principal to have the ec2:DescribeTags IAM permission, fixing a regression introduced in v5.73.0.

---

As additional confirmation that this change no longer results in calls to the DescribeTags API I created a simple configuration with the following subnet data source.

data "aws_subnet" "by_id" {
  id = aws_subnet.test.id
}

After the initial infrastructure is provisioned, this data source is read on every plan operation. By searching the debug logs for a plan operation with v5.76.0 (latest release) and a build from this release branch, it can be confirmed that the data source is no longer making the additional API call.

v5.76.0:

% TF_LOG=debug terraform plan &> plan-old.out
% rg "Action\=DescribeTags" plan-old.out
514:  | Action=DescribeTags&Filter.1.Name=resource-id&Filter.1.Value.1=subnet-0ae0a93e8c9560290&Version=2016-11-15

This branch:

% TF_LOG=debug TF_CLI_CONFIG_FILE=dev.tfrc terraform plan &> plan.out
% rg "Action\=DescribeTags" plan.out
(no results)

Relations

Closes #40104

Output from Acceptance Testing

% make testacc PKG=ec2 TESTS=TestAccVPCSubnetDataSource_
make: Verifying source code with gofmt...
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go1.23.2 test ./internal/service/ec2/... -v -count 1 -parallel 20 -run='TestAccVPCSubnetDataSource_'  -timeout 360m
2024/11/15 10:06:55 Initializing Terraform AWS Provider...

=== NAME  TestAccVPCSubnetDataSource_enableLniAtDeviceIndex
    vpc_subnet_data_source_test.go:197: skipping since no Outposts found
--- SKIP: TestAccVPCSubnetDataSource_enableLniAtDeviceIndex (0.79s)
--- PASS: TestAccVPCSubnetDataSource_tags_EmptyMap (19.23s)
--- PASS: TestAccVPCSubnetDataSource_tags (19.64s)
--- PASS: TestAccVPCSubnetDataSource_tags_NullMap (19.64s)
--- PASS: TestAccVPCSubnetDataSource_tags_IgnoreTags_Overlap_DefaultTag (19.73s)
--- PASS: TestAccVPCSubnetDataSource_tags_DefaultTags_nonOverlapping (19.74s)
--- PASS: TestAccVPCSubnetDataSource_basic (20.45s)
--- PASS: TestAccVPCSubnetDataSource_tags_IgnoreTags_Overlap_ResourceTag (20.92s)
--- PASS: TestAccVPCSubnetDataSource_ipv6ByIPv6CIDRBlock (36.98s)
--- PASS: TestAccVPCSubnetDataSource_ipv6ByIPv6Filter (37.00s)
PASS
ok      github.com/hashicorp/terraform-provider-aws/internal/service/ec2        42.238s

[github-actions]

Community Note

Voting for Prioritization

• Please vote on this pull request by adding a 👍 reaction to the original post to help the community and maintainers prioritize this pull request.
• Please see our prioritization guide for information on how we prioritize.
• Please do not leave "+1" or other comments that do not add relevant new information or questions, they generate extra noise for issue followers and do not help prioritize the request.

For Submitters

• Review the contribution guide relating to the type of change you are making to ensure all of the necessary steps have been taken.
• For new resources and data sources, use skaff to generate scaffolding with comments detailing common expectations.
• Whether or not the branch has been rebased will not impact prioritization, but doing so is always a welcome surprise.

[johnsonaj]

LGTM 🚀

[github-actions]

This functionality has been released in v5.77.0 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 pull request 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 related to this change, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.