Staging can fail when one part exposes top-level `bin`/`lib` as `usr`-merge symlinks (as `base-files` does) and another part produces files under those paths, which is the shape behind the npm plugin failure. This change adds focused regression coverage for that interaction using a minimal reproducer. - **What this covers** - Exercises the stage-time collision path where: - one part provides `bin -> usr/bin` and `lib -> usr/lib` - another part is `usr`-merged and installs content through `bin/` and `lib/` - Verifies the combination stages successfully instead of reporting a directory/symlink conflict - **Test shape** - Adds an integration test in `tests/integration/executor/test_collisions.py` - Uses two `nil` parts to keep the reproducer minimal and local to collision handling: - a `base-files` stand-in that creates the symlinks - an app part with `build-attributes: [enable-usrmerge]` that writes files under `bin/` and `lib/` - **Assertions** - Confirms the staged tree preserves: - `bin -> usr/bin` - `lib -> usr/lib` - Confirms the app payload ends up under: - `usr/bin/www` - `usr/lib/app.js` ```yaml parts: base-files-part: plugin: nil override-build: | mkdir -p "${CRAFT_PART_INSTALL}/usr/bin" "${CRAFT_PART_INSTALL}/usr/lib" ln -s usr/bin "${CRAFT_PART_INSTALL}/bin" ln -s usr/lib "${CRAFT_PART_INSTALL}/lib" app-part: plugin: nil build-attributes: [enable-usrmerge] override-build: | mkdir -p "${CRAFT_PART_INSTALL}/bin" "${CRAFT_PART_INSTALL}/lib" touch "${CRAFT_PART_INSTALL}/bin/www" touch "${CRAFT_PART_INSTALL}/lib/app.js" ``` <!-- START COPILOT CODING AGENT SUFFIX --> - Fixes #1001