Selector: Use shallow document comparisons to avoid IE/Edge cras… (#459)

IE/Edge sometimes crash when comparing documents between frames using the strict
equality operator (`===` & `!==`). Funnily enough, shallow comparisons
(`==` & `!=`) work without crashing.

Fixes jquery/jquery#4441
Closes gh-459
Ref jquery/jquery#4471

Author: mgol

dist/sizzle.js

@@ -6,7 +6,7 @@
  * Released under the MIT license
  * https://js.foundation/
  *
- * Date: 2019-08-20
+ * Date: 2019-10-01
  */
 ( function( window ) {
 var i,
@@ -251,10 +251,7 @@ function Sizzle( selector, context, results, seed ) {
 
 	// Try to shortcut find operations (as opposed to filters) in HTML documents
 	if ( !seed ) {
-
-		if ( ( context ? context.ownerDocument || context : preferredDoc ) !== document ) {
-			setDocument( context );
-		}
+		setDocument( context );
 		context = context || document;
 
 		if ( documentIsHTML ) {
@@ -602,7 +599,11 @@ setDocument = Sizzle.setDocument = function( node ) {
 		doc = node ? node.ownerDocument || node : preferredDoc;
 
 	// Return early if doc is invalid or already selected
-	if ( doc === document || doc.nodeType !== 9 || !doc.documentElement ) {
+	// Support: IE 11+, Edge 17 - 18+
+	// IE/Edge sometimes throw a "Permission denied" error when strict-comparing
+	// two documents; shallow comparisons work.
+	// eslint-disable-next-line eqeqeq
+	if ( doc == document || doc.nodeType !== 9 || !doc.documentElement ) {
 		return document;
 	}
 
@@ -611,9 +612,13 @@ setDocument = Sizzle.setDocument = function( node ) {
 	docElem = document.documentElement;
 	documentIsHTML = !isXML( document );
 
-	// Support: IE 9-11, Edge
+	// Support: IE 9 - 11+, Edge 12 - 18+
 	// Accessing iframe documents after unload throws "permission denied" errors (jQuery #13936)
-	if ( preferredDoc !== document &&
+	// Support: IE 11+, Edge 17 - 18+
+	// IE/Edge sometimes throw a "Permission denied" error when strict-comparing
+	// two documents; shallow comparisons work.
+	// eslint-disable-next-line eqeqeq
+	if ( preferredDoc != document &&
 		( subWindow = document.defaultView ) && subWindow.top !== subWindow ) {
 
 		// Support: IE 11, Edge
@@ -928,7 +933,11 @@ setDocument = Sizzle.setDocument = function( node ) {
 		}
 
 		// Calculate position if both inputs belong to the same document
-		compare = ( a.ownerDocument || a ) === ( b.ownerDocument || b ) ?
+		// Support: IE 11+, Edge 17 - 18+
+		// IE/Edge sometimes throw a "Permission denied" error when strict-comparing
+		// two documents; shallow comparisons work.
+		// eslint-disable-next-line eqeqeq
+		compare = ( a.ownerDocument || a ) == ( b.ownerDocument || b ) ?
 			a.compareDocumentPosition( b ) :
 
 			// Otherwise we know they are disconnected
@@ -939,13 +948,20 @@ setDocument = Sizzle.setDocument = function( node ) {
 			( !support.sortDetached && b.compareDocumentPosition( a ) === compare ) ) {
 
 			// Choose the first element that is related to our preferred document
-			if ( a === document ||
-				a.ownerDocument === preferredDoc &&
+			// Support: IE 11+, Edge 17 - 18+
+			// IE/Edge sometimes throw a "Permission denied" error when strict-comparing
+			// two documents; shallow comparisons work.
+			// eslint-disable-next-line eqeqeq
+			if ( a == document || a.ownerDocument == preferredDoc &&
 				contains( preferredDoc, a ) ) {
 				return -1;
 			}
-			if ( b === document ||
-				b.ownerDocument === preferredDoc &&
+
+			// Support: IE 11+, Edge 17 - 18+
+			// IE/Edge sometimes throw a "Permission denied" error when strict-comparing
+			// two documents; shallow comparisons work.
+			// eslint-disable-next-line eqeqeq
+			if ( b == document || b.ownerDocument == preferredDoc &&
 				contains( preferredDoc, b ) ) {
 				return 1;
 			}
@@ -975,8 +991,14 @@ setDocument = Sizzle.setDocument = function( node ) {
 
 		// Parentless nodes are either documents or disconnected
 		if ( !aup || !bup ) {
-			return a === document ? -1 :
-				b === document ? 1 :
+
+			// Support: IE 11+, Edge 17 - 18+
+			// IE/Edge sometimes throw a "Permission denied" error when strict-comparing
+			// two documents; shallow comparisons work.
+			/* eslint-disable eqeqeq */
+			return a == document ? -1 :
+				b == document ? 1 :
+				/* eslint-enable eqeqeq */
 				aup ? -1 :
 				bup ? 1 :
 				sortInput ?
@@ -1009,8 +1031,13 @@ setDocument = Sizzle.setDocument = function( node ) {
 			siblingCheck( ap[ i ], bp[ i ] ) :
 
 			// Otherwise nodes in our document sort first
-			ap[ i ] === preferredDoc ? -1 :
-			bp[ i ] === preferredDoc ? 1 :
+			// Support: IE 11+, Edge 17 - 18+
+			// IE/Edge sometimes throw a "Permission denied" error when strict-comparing
+			// two documents; shallow comparisons work.
+			/* eslint-disable eqeqeq */
+			ap[ i ] == preferredDoc ? -1 :
+			bp[ i ] == preferredDoc ? 1 :
+			/* eslint-enable eqeqeq */
 			0;
 	};
 
@@ -1022,11 +1049,7 @@ Sizzle.matches = function( expr, elements ) {
 };
 
 Sizzle.matchesSelector = function( elem, expr ) {
-
-	// Set document vars if needed
-	if ( ( elem.ownerDocument || elem ) !== document ) {
-		setDocument( elem );
-	}
+	setDocument( elem );
 
 	if ( support.matchesSelector && documentIsHTML &&
 		!nonnativeSelectorCache[ expr + " " ] &&
@@ -1055,7 +1078,11 @@ Sizzle.matchesSelector = function( elem, expr ) {
 Sizzle.contains = function( context, elem ) {
 
 	// Set document vars if needed
-	if ( ( context.ownerDocument || context ) !== document ) {
+	// Support: IE 11+, Edge 17 - 18+
+	// IE/Edge sometimes throw a "Permission denied" error when strict-comparing
+	// two documents; shallow comparisons work.
+	// eslint-disable-next-line eqeqeq
+	if ( ( context.ownerDocument || context ) != document ) {
 		setDocument( context );
 	}
 	return contains( context, elem );
@@ -1064,7 +1091,11 @@ Sizzle.contains = function( context, elem ) {
 Sizzle.attr = function( elem, name ) {
 
 	// Set document vars if needed
-	if ( ( elem.ownerDocument || elem ) !== document ) {
+	// Support: IE 11+, Edge 17 - 18+
+	// IE/Edge sometimes throw a "Permission denied" error when strict-comparing
+	// two documents; shallow comparisons work.
+	// eslint-disable-next-line eqeqeq
+	if ( ( elem.ownerDocument || elem ) != document ) {
 		setDocument( elem );
 	}
 
@@ -2098,7 +2129,12 @@ function matcherFromGroupMatchers( elementMatchers, setMatchers ) {
 				len = elems.length;
 
 			if ( outermost ) {
-				outermostContext = context === document || context || outermost;
+
+				// Support: IE 11+, Edge 17 - 18+
+				// IE/Edge sometimes throw a "Permission denied" error when strict-comparing
+				// two documents; shallow comparisons work.
+				// eslint-disable-next-line eqeqeq
+				outermostContext = context == document || context || outermost;
 			}
 
 			// Add elements passing elementMatchers directly to results
@@ -2107,7 +2143,12 @@ function matcherFromGroupMatchers( elementMatchers, setMatchers ) {
 			for ( ; i !== len && ( elem = elems[ i ] ) != null; i++ ) {
 				if ( byElement && elem ) {
 					j = 0;
-					if ( !context && elem.ownerDocument !== document ) {
+
+					// Support: IE 11+, Edge 17 - 18+
+					// IE/Edge sometimes throw a "Permission denied" error when strict-comparing
+					// two documents; shallow comparisons work.
+					// eslint-disable-next-line eqeqeq
+					if ( !context && elem.ownerDocument != document ) {
 						setDocument( elem );
 						xml = !documentIsHTML;
 					}