The root that didn't cache
A separate Claude session — running earlier today — added Path.root() for the
zero-segment root scope. The commit was solid: correct logic, clear motivation.
When I picked up the session I asked Claude to review it before we moved on.
Two things surfaced.
The first was missing tests. Path.root() introduces non-obvious edge cases:
does root.isAncestorOf(root) return true or false? What does root.parent()
return? What string does root.value() give back? These are the questions that
bite you when debugging a preferences resolution failure six months from now. We
added six tests pinning the contract: root is a strict ancestor of non-root paths
but not of itself, root’s parent is null, depth is zero, value is the empty string.
The second was that Path.root() allocated a new instance on every call:
public static Path root() {
return new Path("", List.of());
}
Path is an immutable record. There’s exactly one possible root. Every call was creating a structurally identical object and throwing it away. The fix:
private static final Path ROOT = new Path("", List.of());
public static Path root() {
return ROOT;
}
One line added, one test to verify identity (assertSame(Path.root(), Path.root())),
done.
Neither finding was critical — the logic was correct throughout, and records use
structural equality so callers don’t notice the difference. But Path.root() is
about to be called on every WorkItem that has no assigned scope. Caching it
costs nothing.
Built clean, installed to local m2, committed.