prevent-generated-code-duplication

name	prevent-generated-code-duplication
description	Detect and refactor duplicate logic introduced by generated code, including overlaps between generated artifacts and existing project code.

Goal

Prevent divergence and maintenance risk by consolidating duplicated logic created by code generation or by mixing generated and hand-written code.

When to Use

• New generated files duplicate logic already present in the project.
• Generated output duplicates existing generated modules.
• Generated code and hand-written code implement equivalent validation/parsing/mapping/error handling.
• Reviews identify repeated blocks after schema/code generation.

Rules

1. Treat generated-vs-existing duplication as high-priority technical debt and resolve in the same change when feasible.
2. Prefer extraction to shared runtime modules (helpers/utilities/services), not copy-paste edits across multiple generated files.
3. Keep codegen outputs thin: delegate behavior to shared functions where possible.
4. If generator templates are available, fix duplication at template/source level first.
5. If template-level fix is not feasible, add a small shared abstraction and route both generated and existing code through it.
6. Preserve behavior and public interfaces; avoid broad architecture changes unless required.
7. Validate with lint, typecheck, and relevant tests after deduplication.

Workflow

1. Identify duplicate blocks and classify:
   • generated <-> generated
   • generated <-> hand-written
2. Pick dedup strategy:
   • template fix (preferred)
   • shared helper/module extraction
3. Refactor call sites to shared implementation.
4. Remove duplicated code paths.
5. Run verification (lint + typecheck + tests).
6. Document the dedup decision in change summary.

Output Pattern

1. Duplicates found (files + intent).
2. Chosen dedup strategy and why.
3. Refactored shared location.
4. Verification results.