Quick perf mitigation: precompute NamespaceURL.href

It’s a little bit surprising that the biggest perf hit on this branch comes from `NamespaceURL`! This commit mitigates the biggest hit I see in profiling. After this I’m going to do a brief timeboxed spike into using branded types rather than runtime to clearly distinguish between the inherent pair of nullable strings (namespace URI, prefix). If another commit doesn’t follow this one on the PR, safe to assume I didn’t ultimately pursue that direction (at least for now).

Author: eyelidlessness

packages/xforms-engine/src/lib/names/NamespaceURL.ts

@@ -31,10 +31,14 @@ export class NamespaceURL extends URL {
 			return null;
 		}
 
-		return new this(namespaceURI);
+		return new this(String(namespaceURI));
 	}
 
-	private constructor(namespaceURI: NamespaceURL | string) {
-		super(namespaceURI);
+	override readonly href: string;
+
+	private constructor(href: string) {
+		super(href);
+
+		this.href = href;
 	}
 }