Systematic Type Migration

Overview

When refactoring components to new type-safe implementations, use this systematic workflow to prevent "works in isolation but broken integration" bugs.

Core principle: Integration test FIRST → file-by-file migration → incremental verification → cleanup

The Problem

Recurring issue during major refactoring:

• Old component definitions remain in the codebase
• Some files spawn entities with old types
• Other files query for new types
• Systems become disconnected (queries find zero entities)
• User functionality breaks despite all systems being "properly registered"

Example: After introducing type-safe MovementState enum, if setup.rs spawns entities with the old MovementState but planning.rs queries for the new MovementState, queries will silently fail.