Can Eleventy's incremental build safely roll back after a data‑schema change?

Answer

No – Eleventy’s --incremental flag does not record changes to external JSON or JavaScript data files, so a data‑schema modification will not trigger a rebuild of already‑generated pages. To roll back safely you must invalidate the dependency cache before resuming incremental builds.

Confirmed facts

• Eleventy’s incremental mode caches only template dependencies encountered during rendering.
• It does not track modifications to external data files; therefore a schema change leaves existing pages unchanged until a full rebuild or cache clear occurs.
• Plugins that add data via addGlobalData or similar see the same stale data until the cache is cleared.

Likely explanation

Because the dependency cache is unaware of data‑file alterations, the only way to guarantee that updated (or rolled‑back) data influences output is to force Eleventy to treat the next build as a full one. This is achieved by deleting the .eleventy-cache directory or using the --clean flag with an incremental build.

Steps to safely roll back after a data‑schema change

1. Stop any running eleventy --incremental --watch process.
2. Remove the cache: rm -rf .eleventy-cache (or run eleventy --incremental --clean).
3. Restart the incremental build (with or without watch mode). This will regenerate all pages, applying the new or reverted data schema.
4. Resume normal incremental development; subsequent changes to templates or data will again be cached efficiently.

Missing diagnostic detail

If you are using a custom data plugin that loads data from a source outside the project folder (e.g., a remote API), let me know whether the plugin bypasses Eleventy’s data cascade; that would affect whether clearing .eleventy-cache alone is sufficient.