d/aws_default_tags: Fix regression with null vs. empty map

[ewbankkit]

Description

Fixes a v4.36.0 regression where the aws_default_tags data source returns null vs. an empty map ({}) when no default_tags are configured.

Relations

Closes #27372.
Relates #27221.

Output from Acceptance Testing

N.B. unset TF_CLI_CONFIG_FILE before running.

% make testacc TESTARGS='-run=TestAccMetaDefaultTagsDataSource_' PKG=meta 
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test ./internal/service/meta/... -v -count 1 -parallel 20  -run=TestAccMetaDefaultTagsDataSource_ -timeout 180m
=== RUN   TestAccMetaDefaultTagsDataSource_basic
=== PAUSE TestAccMetaDefaultTagsDataSource_basic
=== RUN   TestAccMetaDefaultTagsDataSource_empty
=== PAUSE TestAccMetaDefaultTagsDataSource_empty
=== RUN   TestAccMetaDefaultTagsDataSource_multiple
=== PAUSE TestAccMetaDefaultTagsDataSource_multiple
=== RUN   TestAccMetaDefaultTagsDataSource_ignore
=== PAUSE TestAccMetaDefaultTagsDataSource_ignore
=== CONT  TestAccMetaDefaultTagsDataSource_basic
=== CONT  TestAccMetaDefaultTagsDataSource_multiple
=== CONT  TestAccMetaDefaultTagsDataSource_ignore
=== CONT  TestAccMetaDefaultTagsDataSource_empty
--- PASS: TestAccMetaDefaultTagsDataSource_basic (9.45s)
--- PASS: TestAccMetaDefaultTagsDataSource_multiple (9.46s)
--- PASS: TestAccMetaDefaultTagsDataSource_empty (9.55s)
--- PASS: TestAccMetaDefaultTagsDataSource_ignore (18.34s)
PASS
ok  	github.com/hashicorp/terraform-provider-aws/internal/service/meta	22.470s

After applying this configuration

provider "aws" {}

data "aws_default_tags" "test" {}

the Terraform state is

{
  "version": 4,
  "terraform_version": "1.0.9",
  "serial": 1,
  "lineage": "b136bdbf-dd55-0303-c702-7f5a900401d1",
  "outputs": {},
  "resources": [
    {
      "mode": "data",
      "type": "aws_default_tags",
      "name": "test",
      "provider": "provider[\"registry.terraform.io/hashicorp/aws\"]",
      "instances": [
        {
          "schema_version": 0,
          "attributes": {
            "id": "aws",
            "tags": {}
          },
          "sensitive_attributes": []
        }
      ]
    }
  ]
}

which matches the v4.35.0 version.
Unfortunately we can't test state migration as described in Migrating from SDK as the provider configuration has to be explictly defined for default_tags.

[github-actions]

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[jar-b]

$ make testacc TESTARGS='-run=TestAccMetaDefaultTagsDataSource_' PKG=meta
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test ./internal/service/meta/... -v -count 1 -parallel 20  -run=TestAccMetaDefaultTagsDataSource_ -timeout 180m
=== RUN   TestAccMetaDefaultTagsDataSource_basic
=== PAUSE TestAccMetaDefaultTagsDataSource_basic
=== RUN   TestAccMetaDefaultTagsDataSource_empty
=== PAUSE TestAccMetaDefaultTagsDataSource_empty
=== RUN   TestAccMetaDefaultTagsDataSource_multiple
=== PAUSE TestAccMetaDefaultTagsDataSource_multiple
=== RUN   TestAccMetaDefaultTagsDataSource_ignore
=== PAUSE TestAccMetaDefaultTagsDataSource_ignore
=== RUN   TestAccMetaDefaultTagsDataSource_MigrateFromPluginSDK_Empty
=== PAUSE TestAccMetaDefaultTagsDataSource_MigrateFromPluginSDK_Empty
=== CONT  TestAccMetaDefaultTagsDataSource_basic
=== CONT  TestAccMetaDefaultTagsDataSource_ignore
=== CONT  TestAccMetaDefaultTagsDataSource_MigrateFromPluginSDK_Empty
=== CONT  TestAccMetaDefaultTagsDataSource_multiple
=== CONT  TestAccMetaDefaultTagsDataSource_empty
--- PASS: TestAccMetaDefaultTagsDataSource_multiple (6.15s)
--- PASS: TestAccMetaDefaultTagsDataSource_basic (6.15s)
--- PASS: TestAccMetaDefaultTagsDataSource_empty (10.08s)
--- PASS: TestAccMetaDefaultTagsDataSource_ignore (13.40s)
--- PASS: TestAccMetaDefaultTagsDataSource_MigrateFromPluginSDK_Empty (24.20s)
PASS
ok      github.com/hashicorp/terraform-provider-aws/internal/service/meta       26.973s

Also verified a local build results in the <v4.35.0 behavior:

$ cat terraform.tfstate
{
  "version": 4,
  "terraform_version": "1.2.9",
  "serial": 3,
  "lineage": "d2c608b8-e9f3-fcf0-e08a-9cdf59522a3f",
  "outputs": {},
  "resources": [
    {
      "mode": "data",
      "type": "aws_default_tags",
      "name": "test",
      "provider": "provider[\"registry.terraform.io/hashicorp/aws\"]",
      "instances": [
        {
          "schema_version": 0,
          "attributes": {
            "id": "aws",
            "tags": {}
          },
          "sensitive_attributes": []
        }
      ]
    }
  ]
}

[jar-b]

LGTM ⚡

[github-actions]

This functionality has been released in v4.36.1 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]

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