Fix: compile closest() selectors once per document in the static scanner (#575) (#595)

StaticElement.closest() handed the raw selector string to css-select's
is() on every ancestor step, recompiling the same selector N times for
an element N levels deep. StaticDocument now caches one compiled
matcher per selector (failed compiles cached as rethrowers so bad
selectors still return null). Findings are byte-identical across the
fixture corpus; scan time drops to ~62% on the fixtures and ~7x faster
on deep-DOM pages.

Prepared with AI assistance (Cursor agent), directed by @abdulwahabone.

Co-authored-by: Cursor <cursoragent@cursor.com>

cli/engine/engines/static-html/css-cascade.mjs

@@ -835,10 +835,11 @@ class StaticElement {
     }
   }
   closest(selector) {
+    const matcher = this._doc.matcherFor(selector);
     let cur = this.node;
     while (cur && cur.type === 'tag') {
       try {
-        if (this._doc.is(cur, selector)) return this._doc.wrap(cur);
+        if (matcher(cur)) return this._doc.wrap(cur);
       } catch {
         return null;
       }
@@ -862,9 +863,10 @@ class StaticDocument {
     this.root = root;
     this.selectAll = modules.selectAll;
     this.selectOne = modules.selectOne;
-    this.is = modules.is;
+    this.compile = modules.compile;
     this.domutils = modules.domutils;
     this._wrappers = new WeakMap();
+    this._compiledSelectors = new Map();
     this._styleMap = new WeakMap();
     this._hoverStyleMap = new WeakMap();
     this._accentDashPseudo = new WeakSet();
@@ -882,6 +884,20 @@ class StaticDocument {
     }
     return wrapped;
   }
+  matcherFor(selector) {
+    let matcher = this._compiledSelectors.get(selector);
+    if (!matcher) {
+      try {
+        matcher = this.compile(selector);
+      } catch (err) {
+        // Cache the failure as a rethrower so a bad selector still reaches
+        // closest()'s catch on every call, first and repeat alike.
+        matcher = () => { throw err; };
+      }
+      this._compiledSelectors.set(selector, matcher);
+    }
+    return matcher;
+  }
   querySelectorAll(selector) {
     try {
       return this.selectAll(selector, this.root.children || []).map(node => this.wrap(node));

cli/engine/engines/static-html/detect-html.mjs

@@ -134,7 +134,7 @@ async function detectHtml(filePath, options = {}) {
         parseDocument: htmlparser2.parseDocument,
         selectAll: cssSelect.selectAll,
         selectOne: cssSelect.selectOne,
-        is: cssSelect.is,
+        compile: cssSelect.compile,
         csstree,
         domutils,
       };