un-monkey-patch OpenElementStack to avoid leaks

A monkey-patch as modified by commit 75a921e
maintains a reference to the most recent JSDOMParse5Adapter (and all its
options) through the push/pop closures. Because the monkey-patches are
never cleaned up, there is always a reference to the most recent
JSDOMParse5Adapter and its related objects.

This fixes jestjs/jest#9507
This may fix jsdom#2757

lib/jsdom/browser/parser/html.js

@@ -16,6 +16,34 @@ const OpenElementStack = require("parse5/lib/parser/open-element-stack");
 const OpenElementStackOriginalPop = OpenElementStack.prototype.pop;
 const OpenElementStackOriginalPush = OpenElementStack.prototype.push;
 
+// Horrible monkey-patch to implement https://github.com/inikulin/parse5/issues/237
+function wrapOpenElementStack(adapter) {
+  OpenElementStack.prototype.push = function (...args) {
+    OpenElementStackOriginalPush.apply(this, args);
+    adapter._currentElement = this.current;
+
+    const after = this.items[this.stackTop];
+    if (after._pushedOnStackOfOpenElements) {
+      after._pushedOnStackOfOpenElements();
+    }
+  };
+  OpenElementStack.prototype.pop = function (...args) {
+    const before = this.items[this.stackTop];
+
+    OpenElementStackOriginalPop.apply(this, args);
+    adapter._currentElement = this.current;
+
+    if (before._poppedOffStackOfOpenElements) {
+      before._poppedOffStackOfOpenElements();
+    }
+  };
+}
+
+function unwrapOpenElementStack() {
+  OpenElementStack.prototype.pop = OpenElementStackOriginalPop;
+  OpenElementStack.prototype.push = OpenElementStackOriginalPush;
+}
+
 class JSDOMParse5Adapter {
   constructor(documentImpl) {
     this._documentImpl = documentImpl;
@@ -24,28 +52,6 @@ class JSDOMParse5Adapter {
     // Since the createElement hook doesn't provide the parent element, we keep track of this using _currentElement:
     // https://github.com/inikulin/parse5/issues/285
     this._currentElement = undefined;
-
-    // Horrible monkey-patch to implement https://github.com/inikulin/parse5/issues/237
-    const adapter = this;
-    OpenElementStack.prototype.push = function (...args) {
-      OpenElementStackOriginalPush.apply(this, args);
-      adapter._currentElement = this.current;
-
-      const after = this.items[this.stackTop];
-      if (after._pushedOnStackOfOpenElements) {
-        after._pushedOnStackOfOpenElements();
-      }
-    };
-    OpenElementStack.prototype.pop = function (...args) {
-      const before = this.items[this.stackTop];
-
-      OpenElementStackOriginalPop.apply(this, args);
-      adapter._currentElement = this.current;
-
-      if (before._poppedOffStackOfOpenElements) {
-        before._poppedOffStackOfOpenElements();
-      }
-    };
   }
 
   _ownerDocument() {
@@ -165,15 +171,25 @@ function parseFragment(markup, contextElement) {
     treeAdapter: new JSDOMParse5Adapter(ownerDocument)
   });
 
-  return parse5.parseFragment(contextElement, markup, config);
+  wrapOpenElementStack(config.treeAdapter);
+  try {
+    return parse5.parseFragment(contextElement, markup, config);
+  } finally {
+    unwrapOpenElementStack();
+  }
 }
 
 function parseIntoDocument(markup, ownerDocument) {
   const config = Object.assign({}, ownerDocument._parseOptions, {
     treeAdapter: new JSDOMParse5Adapter(ownerDocument)
   });
 
-  return parse5.parse(markup, config);
+  wrapOpenElementStack(config.treeAdapter);
+  try {
+    return parse5.parse(markup, config);
+  } finally {
+    unwrapOpenElementStack();
+  }
 }
 
 module.exports = {