Sema module dependency resolution: missing deterministic policy for circular imports

Deterministic Resolution in Sema

Sema does not currently provide configuration options to resolve circular dependencies deterministically. Because the resolver relies on a Directed Acyclic Graph (DAG) to establish build order, any circular import violates the fundamental structure required for a stable build sequence. Consequently, the resolver emits an error when a cycle is detected.

Analysis of Non-Deterministic Behavior

The perceived ambiguity in how Sema reacts to circular imports usually stems from the module discovery order. In the absence of a priority policy, the resolver may identify the "root" of the cycle based on the order in which files are traversed by the file system or the order of import statements. This means that while the build will fail consistently (it will not succeed), the specific error message or the module flagged as the cause of the cycle may shift if filenames are changed or if the environment's file-system traversal differs.

Best Practices for Deterministic Builds

To maintain reproducibility and eliminate non-deterministic failure modes, teams should adopt the following architectural patterns:

• Extract Shared Logic: Identify the common functionality causing the mutual dependency and move it into a new, lower-level module. Both original modules should then import this third module, transforming the cycle into a linear dependency chain.
• Interface Abstraction: Define an abstract interface or type definition in a separate leaf module. Have one module implement the interface and the other depend on the interface rather than the concrete implementation.
• Strict CI Validation: Treat any circular dependency error as a fatal build failure. Do not attempt to bypass these errors with custom loading scripts, as this can lead to partial initialization and undefined runtime behavior.

Future Outlook and Build Scripts

There is currently no documented roadmap for a deterministic "cycle-breaking" policy in future releases. Introducing such a policy would likely require a priority-based weighting system for modules. If implemented, existing build scripts would need to be updated to define these priorities to ensure that the resolution remains consistent across different developer environments.

Verification Step

To verify if your build is failing non-deterministically, rename one of the modules involved in the cycle. If the error message changes the identified "starting point" of the cycle, your environment is relying on discovery order rather than a deterministic policy.