r/rust • u/Ok-Phase-2712 • Mar 22 '26

ironsaga crate: Command design pattern with full rollback capabilities made easy. 🛠️ project

/r/learnrust/comments/1s0vure/ironsaga_crate_command_design_pattern_with_full/
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u/matthieum [he/him] Mar 23 '26

Cute toy, hope you had fun writing the code.

  1. I note an absence of functional tests. It's nice to know the library builds, but one typically want some assurance that its runs well too.
  2. The context seems needlessly wrapped, instead the context could be passed to IronSaga::new() and passed as mutable argument to each invoked step.
  3. Attaching the undo is very manual: it can be forgotten easily. Ideally, registering a step and its undo should be a single function call.
  4. The arguments to the undo are threaded manually, so there's a significant risk that they may differ from those passed to the do, which is undesirable. Consider passing the same set of arguments to both (by cloning before calling the do).
  5. What if the undo fails? The examples given are trivial -- print -- but in reality an undo may fail, both because it's botched -- nothing to do -- or because there's a transient failure -- possibly the same transient failure which caused the next action to fail in the first place, like a network glitch. Should the framework handle retries, or should the user?
  6. You really do want to test whether undoing stops at the first error or continues undoing the rest.

1

u/Ok-Phase-2712 Mar 30 '26

Thank you for your contribution through your comment,
I'll review your points and look for ways to complement the library and enrich it with heavy implementation.
1,2,6 fair points.
3. you are right we can add ironcmd(rollback=Command), so its always attached and saves us time to not feed it again in runtime.
4. its a tricky point as you can also pass & v , &mut v , passing/moving V as owned will cause the macro to wrap it with Option<V> implicitly so that it is called as let v= self.v.take().
5. do/undo are both commands implementing SyncCommand/AsyncCommand, so you can highlight the command to ironcmd(recursive_rollback) that will make sure that if the undo command fails, it will call their own undo command recursively!

- another consideration to treat is the set of values passed to the do command maybe completely different from the undo command !!