Sortable: Allow 0-height containers to be sortable as in 1.12.1

Note that container specific events will not fire when the dragged element
is interacting with zero height containers.

Fixes gh-1998
Closes gh-2008

Co-authored-by: A. Wells <borgboyone@users.noreply.github.com>

tests/unit/sortable/core.js

@@ -42,4 +42,57 @@ QUnit.test( "ui-sortable-handle applied to appropriate element", function( asser
 	assert.equal( el.find( ".ui-sortable-handle" ).length, 0, "class name removed on destroy" );
 } );
 
+// gh-1998
+QUnit.test( "drag & drop works with a zero-height container", function( assert ) {
+	var ready = assert.async();
+	assert.expect( 3 );
+
+	var el = $( "<ul class='list-gh-1998'>\n" +
+		"	<style>" +
+		"		.list-gh-1998 {\n" +
+		"			margin: 0;\n" +
+		"			padding: 0;\n" +
+		"		}\n" +
+		"		.list-item-gh-1998 {\n" +
+		"			float: left;\n" +
+		"			display: block;\n" +
+		"			width: 100px;\n" +
+		"			height: 100px;\n" +
+		"		}\n" +
+		"	</style>\n" +
+		"	<li class='list-item-gh-1998'>Item 1</li>\n" +
+		"	<li class='list-item-gh-1998'>Item 2</li>\n" +
+		"	<li class='list-item-gh-1998'>Item 3</li>\n" +
+		"</ul>" )
+		.sortable()
+		.appendTo( "#qunit-fixture" );
+
+	function step1() {
+		el.find( "li" ).eq( 0 ).simulate( "drag", {
+			dx: 100,
+			dy: 3,
+			moves: 3
+		} );
+		setTimeout( step2 );
+	}
+
+	function step2() {
+		el.find( "li" ).eq( 2 ).simulate( "drag", {
+			dx: -200,
+			dy: -3,
+			moves: 3
+		} );
+		setTimeout( step3 );
+	}
+
+	function step3() {
+		assert.equal( el.find( "li" ).eq( 0 ).text(), "Item 3" );
+		assert.equal( el.find( "li" ).eq( 1 ).text(), "Item 2" );
+		assert.equal( el.find( "li" ).eq( 2 ).text(), "Item 1" );
+		ready();
+	}
+
+	step1();
+} );
+
 } );

ui/widgets/sortable.js

@@ -421,11 +421,6 @@ return $.widget( "ui.sortable", $.ui.mouse, {
 			this.helper[ 0 ].style.top = this.position.top + "px";
 		}
 
-		//Post events to containers
-		this._contactContainers( event );
-
-		if ( this.innermostContainer !== null ) {
-
 		//Do scrolling
 		if ( o.scroll ) {
 			if ( this._scroll( event ) !== false ) {
@@ -492,7 +487,9 @@ return $.widget( "ui.sortable", $.ui.mouse, {
 				break;
 			}
 		}
-		}
+
+		//Post events to containers
+		this._contactContainers( event );
 
 		//Interconnect with droppables
 		if ( $.ui.ddmanager ) {
@@ -888,9 +885,7 @@ return $.widget( "ui.sortable", $.ui.mouse, {
 			this.options.axis === "x" || this._isFloating( this.items[ 0 ].item ) :
 			false;
 
-		if ( this.innermostContainer !== null ) {
 		this._refreshItemPositions( fast );
-		}
 
 		var i, p;
 
@@ -1038,8 +1033,6 @@ return $.widget( "ui.sortable", $.ui.mouse, {
 
 		}
 
-		this.innermostContainer = innermostContainer;
-
 		// If no intersecting containers found, return
 		if ( !innermostContainer ) {
 			return;