Summary

Re-enables BuildModules under nodeLinker: hoisted. Slice 6 (#518) wired the hoisted install pipeline but skipped the build phase entirely because BuildModules walked virtual-store slot directories that don't exist under hoisted. Slice 7 routes the build phase through the slice 4 walker's per-node dir so postinstall scripts can run against the on-disk hoisted tree, with extra_bin_paths gathered from every ancestor node_modules/.bin up to the install root (npm-style ancestor resolution).

Changes

• BuildModules gains two fields:
  • pkg_root_by_key: Option<&HashMap<PackageKey, PathBuf>> — overrides the per-snapshot pkgRoot lookup. Populated by the hoisted linker from DependenciesGraphNode::dir. None for isolated (the VirtualStoreLayout::slot_dir path is used).
  • gather_ancestor_bin_paths: bool — switches extra_bin_paths to the new bin_dirs_in_all_parent_dirs helper, a port of upstream's binDirsInAllParentDirs.
• pkg_root_for_key helper routes between layout-based slot computation (isolated) and the override map (hoisted). Hoisted snapshots absent from the map (walker-dropped — pre-skipped, optional skip) take the same exit as the isolated !pkg_dir.exists() skip.
• InstallFrozenLockfile::run now builds a snapshot-key → first-recorded-dir map from walker_result.graph.values() and threads it (plus gather_ancestor_bin_paths: true) into BuildModules instead of skipping the phase. Multiple graph nodes with the same dep_path (a single physical package nested under siblings via version conflict) collapse to the first entry, matching upstream's pkgRoots[0] pick.
• HoistedLinkerOutput private struct bundles hoisted_locations and pkg_root_by_key so the hoisted-branch return doesn't trip clippy::type_complexity.

Out of scope

• MISSING_HOISTED_LOCATIONS — upstream's error fires when rebuild reads .modules.yaml.hoistedLocations and finds it absent. Pacquet has no rebuild command yet, so the install path always re-runs the walker and never consults the persisted field. Tracked as a follow-up for when pacquet rebuild lands.
• Workspace-aware hoisting (slice 9) and hoistingLimits / externalDependencies (slice 10) remain.

Side-effects-cache key shape is unchanged — it's keyed by pkg_id_with_patch_hash + dep-graph hash, both layout-independent (crates/graph-hasher/src/dep_state.rs).

Test plan

• just ready (1219 tests pass; lint, fmt, typos clean)
• just dylint (perfectionist) clean
• taplo format --check clean
• RUSTDOCFLAGS=\"-D warnings\" cargo doc -p pacquet-package-manager --no-deps clean
• New helper tests in crates/package-manager/src/build_modules/tests.rs:
  • bin_dirs_top_level_hoisted_pkg, bin_dirs_nested_hoisted_pkg, bin_dirs_scoped_pkg_pushes_every_step — pin the wire-format output of the upstream-mirroring helper.
  • pkg_root_for_key_isolated_uses_layout, pkg_root_for_key_hoisted_uses_override, pkg_root_for_key_hoisted_missing_returns_none — cover the isolated pass-through, the hoisted override hit, and the missing-snapshot short-circuit.

End-to-end coverage against the registry-mock with a real lifecycle-script package is left to a follow-up — same status as the slice 6 PR. The slice 6 wiring tests already prove the install-pipeline composition; the slice 7 helper tests prove the per-snapshot lookup contract.

Written by an agent (Claude Code, claude-opus-4-7).

Summary by CodeRabbit

• Bug Fixes

  • Improved hoisted package installation with enhanced package root resolution for lifecycle scripts.
  • Better bin-path discovery across package hierarchies during hoisted installs.
  • Fixed build module execution to correctly handle snapshot-specific configurations in hoisted environments.

• Tests

  • Added comprehensive unit tests for package path resolution and bin-directory discovery logic.