[jeffwidman]

Skip the no-op body of named-edge refresh for nodes with no outgoing dependencies and no children.

Why

While constructing a virtual dependency tree, adding or moving a package refreshes named edges through existing descendants. An empty leaf cannot have an edge to refresh or a descendant to visit, yet it still performs a case-insensitive lookup and enters both child loops.

Return immediately only when edgesOut, children, and fsChildren are all empty. This does not cache emptiness: later dependency or child additions remain visible. Nodes without outgoing dependencies but with package or filesystem children must still be traversed.

The traversal still calls the method for empty leaves; this skips its unnecessary body rather than changing the algorithm's asymptotic complexity. There is no new cache, index, deferred resolution, or intended public API/output change.

Regression tests verify that an empty leaf performs no edge lookup, that adding dependencies later restores normal refresh behavior, and that dependency-free parents still refresh both package and filesystem descendants when targets are added or removed.

Performance

In an offline large-workspace native npm benchmark:

Flow	Median CPU, before -> after	Median wall, before -> after
Lockfile writer	6.389 -> 5.815 s (9.0% lower)	5.325 -> 4.675 s (12.2% lower)
Dry-run checker	5.712 -> 5.063 s (11.4% lower)	4.724 -> 4.022 s (14.9% lower)

The baseline already contains runtime adaptations of #10127, #10128, npm/hosted-git-info#347, and #10130; the candidate adds only this early return. This branch is independently based on latest, not stacked on those PRs.

Method: Node 24.22.0, npm 11.17.0 / Arborist 9.8.0, networking disabled, 4 CPUs / 12 GB, one excluded warmup per arm and three alternating measured pairs. Writer uses --package-lock-only --force --ignore-scripts; checker uses --package-lock-only --dry-run=true --ignore-scripts; both additionally disable audit/funding and use --offline --timing.

All compared manifests, lockfiles (including the writer's hidden lockfile), configuration files, and normalized logs were identical. Separate instrumentation avoided 3,997,148 empty-leaf map lookups, reducing total map gets from 9,439,354 to 5,442,206. A public synthetic tree with 128 dependency-free packages reduced map gets from 8,512 to 256, with the same children and inventory.

Savings overlap the canonical-ASCII map normalization fast path in #10132. A separate five-pair comparison after that fast path still measured:

• Writer CPU 5.375 -> 5.231 s (2.7% lower); wall 4.223 -> 4.022 s (4.8% lower).
• Checker CPU 4.679 -> 4.440 s (5.1% lower); wall 3.672 -> 3.421 s (6.8% lower).

Do not add the standalone percentages together. Tiny seven-pair controls were roughly neutral (standalone CPU -1.5%, wall +0.1%; after the ASCII fast path CPU -0.9%, wall -0.4%). These are workload-specific native-command measurements, not a universal regression-free claim or complete Dependabot job savings.

Validation

On this standalone branch, based on npm 12.2.0 / Arborist 10.0.3, using existing development dependencies:

• node bin/npm-cli.js test --workspace=@npmcli/arborist --ignore-scripts -- --jobs=4 — passed all 59 test files; 100% statements, branches, functions, and lines.
• eslint workspaces/arborist/lib/node.js workspaces/arborist/test/node.js — passed.
• git diff --check — passed.

No snapshots were changed. During the preceding investigation, an additional 24-command offline workspace/lockfile-version matrix passed with this optimization and the ASCII fast path together; the full suite above was rerun with this optimization alone.

The full npm CLI suite and Windows/macOS runs were not performed.

References

Related independent native-work reductions: #10127, #10128, npm/hosted-git-info#347, #10130.

The related normalization fast path is proposed independently in #10132. Neither PR depends on the other.

[Copilot]

🟡 Changes recommended

The test can pass with a stale empty-leaf cache because it never verifies that the leaf’s edge resolves to a new foo inserted under root after detachment.

1 open issue

• Test named-edge refresh after reinserting a detached dependency · New

What changed in this PR

Optimizes Arborist’s named-edge refresh by skipping unnecessary work for empty leaves while preserving traversal through nodes with children.

Changes:

• Return early only when outgoing dependencies, package children, and filesystem children are all empty.
• Add regression tests for skipped lookups, later dependency additions, and descendant updates.

File	Description
workspaces/​arborist/​test/​node.js	Adds empty-leaf and descendant-refresh regression tests.
workspaces/​arborist/​lib/​node.js	Adds the empty-leaf early return to named-edge refresh.

_{Review effort: Max}

[nkolev92]

LGTM.
Copilot's suggested for the test make sense if you'd like to address it.

[Copilot]

🟢 Approval recommended

No active review issues are reported for the empty-leaf refresh optimization.

No open issues 🎉

1 resolved since last review

• Test named-edge refresh after reinserting a detached dependency

_{Review effort: Max}