Migration — Cleanup and Rollback

Final step of ../SKILL.md → Recommended Order, plus the rollback recipe. Run this once per slice, only after the new slice passes tests and the UI flows have been verified.

Remove Old Store Files

Delete the old store file only after tests and UI checks pass. Verify zero references with targeted searches such as grep -rn "{old-store}.store" src/ and grep -rn "from.*stores/{old-store}" src/; both must return no results.

Do not replace the deleted store with a barrel, re-export, or proxy module that keeps the old import path alive. After a migration or refactor, the old module path must be removed, inlined into the new owner, or explicitly kept as a compatibility shim.

Pass-Through Wrapper Guard

Check every old path touched by the migration, not only the .store.svelte.ts file. Thin wrappers include:

• export { ... } from "new/path" or export * from "new/path"
• imports from the new file followed by identical exports
• functions/classes whose only behavior is calling the new implementation

Intentional shims must be rare and documented next to the shim with:

1. The compatibility consumer or release window that still imports the old path
2. The sunset/removal condition
3. The new import path callers should use

Verifier output must say either “no pass-through wrappers” or list each documented compatibility shim and its removal condition.

Rollback Strategy

Keep migrations in small, independently verifiable technical increments. Retain the old store until the replacement is verified, and preserve a recoverable baseline through the active workflow before deleting it. Follow Workflow ownership below for any branch, commit, PR, or history operation.

Workflow ownership

Branching, commits, PR sizing, and rollback commands are governed by the active user/task/repository instructions. This skill does not require a branch, commit, or PR per store and does not authorize destructive history changes. Technical rollback scope remains the complete migrated owner and its consumers.

Reverting a migration

When rollback is authorized, restore the old store and affected consumers from the approved baseline; remove the replacement slice, matching reducer constructor entry, and matching store.runSaga(sagaFn) startup call as one technical unit. Re-run affected tests and UI checks so there is only one active owner.

Minimizing risk

• Run all existing tests after each store migration
• Manually test affected UI flows before handoff
• Keep technical increments small; use Workflow ownership for VCS policy
• Verify zero references to the old store before deleting it: grep -rn "{old-store}" src/ --include="*.ts" --include="*.svelte"

Final Checklist Per Slice

• Reducer registered in the configured Store constructor map
• Any app saga explicitly started with owned cancellation, per ../../store/SKILL.md → App saga lifetime
• All consuming components updated (see ../component-migration/SKILL.md)
• All tests pass
• Manual UI verification done on affected flows
• Old .store.svelte.ts file deleted
• grep confirms zero references to the old store path
• Old module paths checked for one-line re-export/proxy/delegate leftovers
• Any remaining compatibility shim documents the reason and sunset/removal condition
• Handoff identifies the migrated slice and follows Workflow ownership

Cleanup Examples

Document a temporary compatibility shim

/**
 * Compatibility shim for plugin-cart@2.x until that plugin releases its
 * cart selector migration. Remove after plugin-cart >= 3.0 is required.
 * New callers must import from "$lib/store/slices/cart/cart-selectors".
 */
export { selectCartTotal } from "$lib/store/slices/cart/cart-selectors";

Record per-slice cleanup evidence

Record actual search queries/results, consumer import replacements, tests, UI flows, and wrapper/shim findings together. This example is a report shape, not proof of a run: only delete when tests/UI pass and old-path searches are empty. If Header.svelte or Checkout.svelte still imports the old store, deletion is unsafe regardless of whether the replacement itself passes tests.

export const cartCleanupReport = {
  slice: "cart",
  removedStoreFiles: ["src/lib/stores/cart.store.svelte.ts"],
  searches: [
    { query: "cart.store.svelte", matches: [] },
    { query: "from.*stores/cart", matches: [] },
  ],
  importReplacements: [{
    consumer: "src/routes/cart/CartSummary.svelte",
    removedImport: "$lib/stores/cart.store.svelte",
    addedImports: [
      "$lib/store/slices/cart/cart-selectors",
      "$lib/store/slices/cart/cart-slice",
      "$lib/store/store",
    ],
  }],
  passThroughWrappers: [],
  documentedShims: [],
  verification: ["cart reducer tests", "cart saga tests", "cart checkout manual flow"],
};