r/db_instance: Fix bug introduced v3.29.0, name, snapshot conflicts

[anGie44]

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Closes #17712, closes #17722
Relates #17037, #17156

Output from acceptance testing:

--- PASS: TestAccAWSDBInstance_MySQL_SnapshotRestoreWithEngineVersion (1192.86s)

Notes

• changes here revert those originally introduced (RDS - Throw error when name or username supplied on DB snapshot restore #17156) to address RDS instance got recreated after another apply without any change #17037

[YakDriver]

Here is a sum up of what we've learned going through this.

Original issue #17037 resulted in fix #17156. However, #17037 did not include any configuration detailing how the problem occurred and merely that a problem had occurred. Unfortunately, the speculative fix in #17156 could not have fixed the issue. The #17037 op was concerned about a diff (ForceNew) and all that the #17156 fix did was throw new errors. Throwing errors cannot resolve erroneous diffs.

#17156 resulted in many kinds of problems noted in #17712 and #17722. For example, the ConflictsWith addition instantly errored configs with empty snapshot_identifiers but name. Next, when restoring from an instance with a name to an instance without name but with snapshot_identifier, you'd receive an error on the second apply because of the computed name. For example, the config below should be valid but #17156 checks caused the error:

resource "aws_db_instance" "db" {
  allocated_storage    = 5
  engine               = "mysql"
  engine_version       = "5.7"
  instance_class       = "db.t3.micro"
  deletion_protection  = false
  skip_final_snapshot  = true
  snapshot_identifier  = aws_db_snapshot.test.db_snapshot_identifier
  tags = {
    "foo" = "bar"
  }
  identifier         = "yakdriver-tf-acc-target"
  maintenance_window = "Sun:00:00-Sun:08:00"
}

resource "aws_db_instance" "source" {
  allocated_storage    = 5
  engine               = "mysql"
  engine_version       = "5.7"
  identifier           = "yakdriver-tf-acc-source"
  instance_class       = "db.t3.micro"
  name                 = "yakdrivertfaccdbtesst"
  password             = "avoid-plaintext-passwords"
  username             = "tfacctest"
  skip_final_snapshot  = true
}

resource "aws_db_snapshot" "test" {
  db_instance_identifier = aws_db_instance.source.id
  db_snapshot_identifier = "yakdriver-tf-acc-snap"
}

[YakDriver]

Looking good! 🎉

This is reverting a previous change that didn't include new acceptances tests so I'm using a random set of acceptance tests to ensure nothing went awry. (Daily tests will ensure the rest work as well.)

GovCloud:

--- PASS: TestAccAWSDBInstance_MinorVersion (330.86s)
--- PASS: TestAccAWSDBInstance_namePrefix (362.36s)
--- PASS: TestAccAWSDBInstance_DeletionProtection (399.23s)
--- PASS: TestAccAWSDBInstance_basic (448.55s)
--- PASS: TestAccAWSDBInstance_kmsKey (452.26s)
--- PASS: TestAccAWSDBInstance_EnabledCloudwatchLogsExports_Postgresql (470.55s)
--- PASS: TestAccAWSDBInstance_Password (474.81s)
--- PASS: TestAccAWSDBInstance_iamAuth (498.87s)
--- PASS: TestAccAWSDBInstance_IsAlreadyBeingDeleted (525.67s)
--- PASS: TestAccAWSDBInstance_DbSubnetGroupName (531.73s)
--- PASS: TestAccAWSDBInstance_DbSubnetGroupName_VpcSecurityGroupIds (531.89s)

us-west-2:

--- PASS: TestAccAWSDBInstance_CACertificateIdentifier (330.23s)
--- PASS: TestAccAWSDBInstance_generatedName (382.24s)
--- PASS: TestAccAWSDBInstance_DbSubnetGroupName_VpcSecurityGroupIds (489.53s)
--- PASS: TestAccAWSDBInstance_MaxAllocatedStorage (505.53s)
--- PASS: TestAccAWSDBInstance_optionGroup (530.20s)
--- PASS: TestAccAWSDBInstance_cloudwatchLogsExportConfiguration (564.96s)
--- PASS: TestAccAWSDBInstance_portUpdate (645.56s)
--- PASS: TestAccAWSDBInstance_EnabledCloudwatchLogsExports_MSSQL (677.47s)
--- PASS: TestAccAWSDBInstance_MonitoringRoleArn_RemovedToEnabled (724.28s)
--- PASS: TestAccAWSDBInstance_NoDeleteAutomatedBackups (737.83s)
--- PASS: TestAccAWSDBInstance_FinalSnapshotIdentifier_SkipFinalSnapshot (789.48s)
--- PASS: TestAccAWSDBInstance_FinalSnapshotIdentifier (832.39s)
--- PASS: TestAccAWSDBInstance_EnabledCloudwatchLogsExports_Oracle (832.94s)

[ghost]

This has been released in version 3.29.1 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 for triage. Thanks!

[ghost]

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 feel this issue should be reopened, we encourage creating a new issue linking back to this one for added context. Thanks!