feat: support destroy_execution_order_group

[romuloslv]

what

This pull request enables destroy_execution_order_group

why

To support reverse execution order during destroy operations atlantis plan/apply -- -destroy. Currently, Atlantis supports execution_order_group for both resource creation and destruction. However, when hierarchical dependencies orchestrated by Terragrunt are present, resource destruction must be performed in reverse order, ensuring that child resources are removed before their parent resources. The implementation adds automatic detection of the -destroy flag, calculates effective execution groups based on operation type, and maintains backward compatibility with existing configurations. Both destructive and non-destructive global plan/apply operations work correctly in the same PR - regular operations use execution_order_group while destroy operations use destroy_execution_order_group, allowing users to safely test both creation and destruction workflows before merging.

tests

Tests added in

• server/core/config/raw/project_test.go
• server/events/apply_command_runner_test.go
• server/events/plan_command_runner_test.go
• server/events/project_command_pool_executor_test.go

references

• atlantis + terragrunt: dependent modules can't be applied in one go #2243

[matheuslisboa-pp]

Very welcome contribution @romuloslv! looking forward to use it!!

[dawittbarbara]

This contribution is very important for various resources. RDS is very complex to destroy. It will certainly help many people.

Congratulations @romuloslv , may it be approved soon and go into production.

[lukemassa]

There has been some discussion of order groups vs depends on, and how we might want to try to collapse those two concepts into one, I'm not sure if/how that's relevant here, thoughts @jamengual ?

[jamengual]

yes, anything related to execution groups or sequence of executions needs to wait until we figure out the best approach.

[romuloslv]

@lukemassa, @jamengual

I agree regarding the integration between the two concepts execution_order_group/depends_on. Even though I understand that the intention is a 1:N relationship for one and 1:1 for the other, this can still create some difficulty for certain users.

Currently, for Terragrunt-based workflows, we can configure the following keys in atlantis.yaml:

• Only depends_on: Does not respect plan/apply ordering (everything starts at the same time).
• Only execution_order_group: Respects the group ordering 0,1,2. (Creation works, but destructive plan/apply does not, since it follows the same creation order.)
• Both execution_order_group and depends_on: Respects the group ordering 0,1,2. (The dependency is created, but Atlantis will not apply the dependent projects, always returning the message: Can't apply your project unless you apply its dependencies)

In an ideal scenario, I would like to define the key(s) in atlantis.yaml and successfully execute, within a PR, the following commands: atlantis plan, atlantis apply, atlantis plan -- -destroy, atlantis apply -- -destroy.

@jamengual you mentioned that not all maintainers are able to use Terragrunt for testing, and that PRs are welcome. I can contribute, including running tests, if there is any guidance on how we should handle dependency scenarios within Atlantis.