Core:Selector: Move jQuery.contains from the selector to the core module

The `jQuery.contains` method is quite simple in jQuery 4+. On the other side,
it's a dependency of the core `isAttached` util which is not ideal; moving
it from the `selector` the `core` module resolves the issue.

Closes gh-5167

7 files changed, 70 insertions, 74 deletions

diff --git a/src/core.js b/src/core.js
index 4f5731ae1..16cd9a7c7 100644
--- a/src/core.js
+++ b/src/core.js
@@ -314,6 +314,20 @@ jQuery.extend( {
 		return !rhtmlSuffix.test( namespace || docElem && docElem.nodeName || "HTML" );
 	},
 
+	// Note: an element does not contain itself
+	contains: function( a, b ) {
+		var bup = b && b.parentNode;
+
+		return a === bup || !!( bup && bup.nodeType === 1 && (
+
+			// Support: IE 9 - 11+
+			// IE doesn't have `contains` on SVG.
+			a.contains ?
+				a.contains( bup ) :
+				a.compareDocumentPosition && a.compareDocumentPosition( bup ) & 16
+		) );
+	},
+
 	merge: function( first, second ) {
 		var len = +second.length,
 			j = 0,
diff --git a/src/core/isAttached.js b/src/core/isAttached.js
index 9c57a4741..72c7bbda4 100644
--- a/src/core/isAttached.js
+++ b/src/core/isAttached.js
@@ -1,8 +1,6 @@
 import jQuery from "../core.js";
 import documentElement from "../var/documentElement.js";
 
-import "../selector/contains.js"; // jQuery.contains
-
 var isAttached = function( elem ) {
 		return jQuery.contains( elem.ownerDocument, elem ) ||
 			elem.getRootNode( composed ) === elem.ownerDocument;
diff --git a/src/selector-native.js b/src/selector-native.js
index 0e2e48d81..7ca500515 100644
--- a/src/selector-native.js
+++ b/src/selector-native.js
@@ -30,7 +30,6 @@ import documentElement from "./var/documentElement.js";
 import whitespace from "./var/whitespace.js";
 
 // The following utils are attached directly to the jQuery object.
-import "./selector/contains.js";
 import "./selector/escapeSelector.js";
 import "./selector/uniqueSort.js";
 
diff --git a/src/selector.js b/src/selector.js
index a69e16556..e6ec6a326 100644
--- a/src/selector.js
+++ b/src/selector.js
@@ -12,7 +12,6 @@ import isIE from "./var/isIE.js";
 import support from "./selector/support.js";
 
 // The following utils are attached directly to the jQuery object.
-import "./selector/contains.js";
 import "./selector/escapeSelector.js";
 import "./selector/uniqueSort.js";
 
diff --git a/src/selector/contains.js b/src/selector/contains.js
deleted file mode 100644
index 137b54388..000000000
--- a/src/selector/contains.js
+++ /dev/null
@@ -1,15 +0,0 @@
-import jQuery from "../core.js";
-
-// Note: an element does not contain itself
-jQuery.contains = function( a, b ) {
-	var bup = b && b.parentNode;
-
-	return a === bup || !!( bup && bup.nodeType === 1 && (
-
-		// Support: IE 9 - 11+
-		// IE doesn't have `contains` on SVG.
-		a.contains ?
-			a.contains( bup ) :
-			a.compareDocumentPosition && a.compareDocumentPosition( bup ) & 16
-	) );
-};
diff --git a/test/unit/core.js b/test/unit/core.js
index b4bd5838c..49b7aa607 100644
--- a/test/unit/core.js
+++ b/test/unit/core.js
@@ -1557,3 +1557,59 @@ QUnit[ includesModule( "deferred" ) ? "test" : "skip" ]( "jQuery.readyException
 		throw new Error( "Error in jQuery ready" );
 	} );
 } );
+
+QUnit.test( "jQuery.contains", function( assert ) {
+	assert.expect( 16 );
+
+	var container = document.getElementById( "nonnodes" ),
+		element = container.firstChild,
+		text = element.nextSibling,
+		nonContained = container.nextSibling,
+		detached = document.createElement( "a" );
+	assert.ok( element && element.nodeType === 1, "preliminary: found element" );
+	assert.ok( text && text.nodeType === 3, "preliminary: found text" );
+	assert.ok( nonContained, "preliminary: found non-descendant" );
+	assert.ok( jQuery.contains( container, element ), "child" );
+	assert.ok( jQuery.contains( container.parentNode, element ), "grandchild" );
+	assert.ok( jQuery.contains( container, text ), "text child" );
+	assert.ok( jQuery.contains( container.parentNode, text ), "text grandchild" );
+	assert.ok( !jQuery.contains( container, container ), "self" );
+	assert.ok( !jQuery.contains( element, container ), "parent" );
+	assert.ok( !jQuery.contains( container, nonContained ), "non-descendant" );
+	assert.ok( !jQuery.contains( container, document ), "document" );
+	assert.ok( !jQuery.contains( container, document.documentElement ), "documentElement (negative)" );
+	assert.ok( !jQuery.contains( container, null ), "Passing null does not throw an error" );
+	assert.ok( jQuery.contains( document, document.documentElement ), "documentElement (positive)" );
+	assert.ok( jQuery.contains( document, element ), "document container (positive)" );
+	assert.ok( !jQuery.contains( document, detached ), "document container (negative)" );
+} );
+
+QUnit.test( "jQuery.contains in SVG (jQuery trac-10832)", function( assert ) {
+	assert.expect( 4 );
+
+	var svg = jQuery(
+		"<svg xmlns='http://www.w3.org/2000/svg' version='1.1' height='1' width='1'>" +
+		"<g><circle cx='1' cy='1' r='1' /></g>" +
+		"</svg>"
+	).appendTo( "#qunit-fixture" )[ 0 ];
+
+	assert.ok( jQuery.contains( svg, svg.firstChild ), "root child" );
+	assert.ok( jQuery.contains( svg.firstChild, svg.firstChild.firstChild ), "element child" );
+	assert.ok( jQuery.contains( svg, svg.firstChild.firstChild ), "root granchild" );
+	assert.ok( !jQuery.contains( svg.firstChild.firstChild, svg.firstChild ),
+		"parent (negative)" );
+} );
+
+QUnit.testUnlessIE( "jQuery.contains within <template/> doesn't throw (gh-5147)", function( assert ) {
+	assert.expect( 1 );
+
+	var template = jQuery( "<template><div><div class='a'></div></div></template>" ),
+		a = jQuery( template[ 0 ].content ).find( ".a" );
+
+	template.appendTo( "#qunit-fixture" );
+
+	jQuery.contains( a[ 0 ].ownerDocument, a[ 0 ] );
+
+	assert.ok( true, "Didn't throw" );
+} );
+
diff --git a/test/unit/selector.js b/test/unit/selector.js
index 720d2ddf5..0057fe57a 100644
--- a/test/unit/selector.js
+++ b/test/unit/selector.js
@@ -1853,61 +1853,6 @@ testIframe(
 	}
 );
 
-QUnit.test( "jQuery.contains", function( assert ) {
-	assert.expect( 16 );
-
-	var container = document.getElementById( "nonnodes" ),
-		element = container.firstChild,
-		text = element.nextSibling,
-		nonContained = container.nextSibling,
-		detached = document.createElement( "a" );
-	assert.ok( element && element.nodeType === 1, "preliminary: found element" );
-	assert.ok( text && text.nodeType === 3, "preliminary: found text" );
-	assert.ok( nonContained, "preliminary: found non-descendant" );
-	assert.ok( jQuery.contains( container, element ), "child" );
-	assert.ok( jQuery.contains( container.parentNode, element ), "grandchild" );
-	assert.ok( jQuery.contains( container, text ), "text child" );
-	assert.ok( jQuery.contains( container.parentNode, text ), "text grandchild" );
-	assert.ok( !jQuery.contains( container, container ), "self" );
-	assert.ok( !jQuery.contains( element, container ), "parent" );
-	assert.ok( !jQuery.contains( container, nonContained ), "non-descendant" );
-	assert.ok( !jQuery.contains( container, document ), "document" );
-	assert.ok( !jQuery.contains( container, document.documentElement ), "documentElement (negative)" );
-	assert.ok( !jQuery.contains( container, null ), "Passing null does not throw an error" );
-	assert.ok( jQuery.contains( document, document.documentElement ), "documentElement (positive)" );
-	assert.ok( jQuery.contains( document, element ), "document container (positive)" );
-	assert.ok( !jQuery.contains( document, detached ), "document container (negative)" );
-} );
-
-QUnit.test( "jQuery.contains in SVG (jQuery trac-10832)", function( assert ) {
-	assert.expect( 4 );
-
-	var svg = jQuery(
-		"<svg xmlns='http://www.w3.org/2000/svg' version='1.1' height='1' width='1'>" +
-		"<g><circle cx='1' cy='1' r='1' /></g>" +
-		"</svg>"
-	).appendTo( "#qunit-fixture" )[ 0 ];
-
-	assert.ok( jQuery.contains( svg, svg.firstChild ), "root child" );
-	assert.ok( jQuery.contains( svg.firstChild, svg.firstChild.firstChild ), "element child" );
-	assert.ok( jQuery.contains( svg, svg.firstChild.firstChild ), "root granchild" );
-	assert.ok( !jQuery.contains( svg.firstChild.firstChild, svg.firstChild ),
-		"parent (negative)" );
-} );
-
-QUnit.testUnlessIE( "jQuery.contains within <template/> doesn't throw (gh-5147)", function( assert ) {
-	assert.expect( 1 );
-
-	var template = jQuery( "<template><div><div class='a'></div></div></template>" ),
-		a = jQuery( template[ 0 ].content ).find( ".a" );
-
-	template.appendTo( "#qunit-fixture" );
-
-	jQuery.contains( a[ 0 ].ownerDocument, a[ 0 ] );
-
-	assert.ok( true, "Didn't throw" );
-} );
-
 QUnit.test( "find in document fragments", function( assert ) {
 	assert.expect( 1 );