Selector: Patch & warn against legacy selector pseudos

src/jquery/core.js

@@ -102,12 +102,6 @@ migratePatchAndWarnFunc( jQuery, "holdReady", jQuery.holdReady,
 migratePatchAndWarnFunc( jQuery, "unique", jQuery.uniqueSort,
 	"unique", "jQuery.unique is deprecated; use jQuery.uniqueSort" );
 
-// Now jQuery.expr.pseudos is the standard incantation
-migrateWarnProp( jQuery.expr, "filters", jQuery.expr.pseudos, "expr-pre-pseudos",
-	"jQuery.expr.filters is deprecated; use jQuery.expr.pseudos" );
-migrateWarnProp( jQuery.expr, ":", jQuery.expr.pseudos, "expr-pre-pseudos",
-	"jQuery.expr[':'] is deprecated; use jQuery.expr.pseudos" );
-
 // Prior to jQuery 3.1.1 there were internal refs so we don't warn there
 if ( jQueryVersionSince( "3.1.1" ) ) {
 	migratePatchAndWarnFunc( jQuery, "trim", function( text ) {

src/jquery/selector.js

@@ -0,0 +1,69 @@
+import { migratePatchFunc, migrateWarnProp, migrateWarn } from "../main.js";
+
+// Now jQuery.expr.pseudos is the standard incantation
+migrateWarnProp( jQuery.expr, "filters", jQuery.expr.pseudos, "expr-pre-pseudos",
+	"jQuery.expr.filters is deprecated; use jQuery.expr.pseudos" );
+migrateWarnProp( jQuery.expr, ":", jQuery.expr.pseudos, "expr-pre-pseudos",
+	"jQuery.expr[':'] is deprecated; use jQuery.expr.pseudos" );
+
+function markFunction( fn ) {
+	fn[ jQuery.expando ] = true;
+	return fn;
+}
+
+migratePatchFunc( jQuery.expr.filter, "PSEUDO", function( pseudo, argument ) {
+
+	// pseudo-class names are case-insensitive
+	// https://www.w3.org/TR/selectors/#pseudo-classes
+	// Prioritize by case sensitivity in case custom pseudos are added with uppercase letters
+	// Remember that setFilters inherits from pseudos
+	var args,
+		fn = jQuery.expr.pseudos[ pseudo ] ||
+			jQuery.expr.setFilters[ pseudo.toLowerCase() ] ||
+			jQuery.error( "Syntax error, unrecognized expression: unsupported pseudo: " + pseudo );
+
+	// The user may use createPseudo to indicate that
+	// arguments are needed to create the filter function
+	// just as jQuery does
+	if ( fn[ jQuery.expando ] ) {
+		return fn( argument );
+	}
+
+	// But maintain support for old signatures
+	if ( fn.length > 1 ) {
+		migrateWarn( "legacy-custom-pseudos",
+			"Pseudos with multiple arguments are deprecated; " +
+				"use jQuery.expr.createPseudo()" );
+		args = [ pseudo, pseudo, "", argument ];
+		return jQuery.expr.setFilters.hasOwnProperty( pseudo.toLowerCase() ) ?
+			markFunction( function( seed, matches ) {
+				var idx,
+					matched = fn( seed, argument ),
+					i = matched.length;
+				while ( i-- ) {
+					idx = Array.prototype.indexOf.call( seed, matched[ i ] );
+					seed[ idx ] = !( matches[ idx ] = matched[ i ] );
+				}
+			} ) :
+			function( elem ) {
+				return fn( elem, 0, args );
+			};
+	}
+
+	return fn;
+}, "legacy-custom-pseudos" );
+
+if ( typeof Proxy !== "undefined" ) {
+	jQuery.each( [ "pseudos", "setFilters" ], function( _, api ) {
+		jQuery.expr[ api ] = new Proxy( jQuery.expr[ api ], {
+			set: function( _target, _prop, fn ) {
+				if ( typeof fn === "function" && !fn[ jQuery.expando ] && fn.length > 1 ) {
+					migrateWarn( "legacy-custom-pseudos",
+						"Pseudos with multiple arguments are deprecated; " +
+							"use jQuery.expr.createPseudo()" );
+				}
+				return Reflect.set.apply( this, arguments );
+			}
+		} );
+	} );
+}

src/migrate.js

@@ -2,6 +2,7 @@ import "./version.js";
 import "./compareVersions.js";
 import "./main.js";
 import "./jquery/core.js";
+import "./jquery/selector.js";
 import "./jquery/ajax.js";
 import "./jquery/attributes.js";
 import "./jquery/css.js";

test/data/testinit.js

@@ -64,13 +64,14 @@
 				"unit/jquery/attributes.js",
 				"unit/jquery/css.js",
 				"unit/jquery/data.js",
+				"unit/jquery/deferred.js",
 				"unit/jquery/effects.js",
 				"unit/jquery/event.js",
 				"unit/jquery/manipulation.js",
 				"unit/jquery/offset.js",
+				"unit/jquery/selector.js",
 				"unit/jquery/serialize.js",
-				"unit/jquery/traversing.js",
-				"unit/jquery/deferred.js"
+				"unit/jquery/traversing.js"
 			];
 
 		testFiles.forEach( function( testFile ) {

test/runner/flags/modules.js

@@ -5,11 +5,12 @@ export const modules = [
 	"attributes",
 	"css",
 	"data",
+	"deferred",
 	"effects",
 	"event",
 	"manipulation",
 	"offset",
+	"selector",
 	"serialize",
-	"traversing",
-	"deferred"
+	"traversing"
 ];

test/unit/jquery/core.js

@@ -315,35 +315,6 @@ QUnit.test( "jQuery.unique", function( assert ) {
 	} );
 } );
 
-QUnit.test( "jQuery.expr.pseudos aliases", function( assert ) {
-	assert.expect( 7 );
-
-	expectWarning( assert, "jQuery.expr.filters", function() {
-		jQuery.expr.filters.mazda = function( elem ) {
-			return elem.style.zoom === "3";
-		};
-	} );
-
-	expectWarning( assert, "jQuery.expr[':']", function() {
-		jQuery.expr[ ":" ].marginal = function( elem ) {
-			return parseInt( elem.style.marginLeftWidth ) > 20;
-		};
-	} );
-
-	expectNoWarning( assert, "jQuery.expr.pseudos", function() {
-		var fixture = jQuery( "#qunit-fixture" ).prepend( "<p>hello</p>" );
-
-		assert.ok( jQuery.expr.pseudos.mazda, "filters assigned" );
-		assert.ok( jQuery.expr.pseudos.marginal, "[':'] assigned" );
-		fixture.find( "p" ).first().css( "marginLeftWidth", "40px" );
-		assert.equal( fixture.find( "p:marginal" ).length, 1, "One marginal element" );
-		assert.equal( fixture.find( "div:mazda" ).length, 0, "No mazda elements" );
-		delete jQuery.expr.pseudos.mazda;
-		delete jQuery.expr.pseudos.marginal;
-	} );
-
-} );
-
 QUnit.test( "jQuery.holdReady (warn only)", function( assert ) {
 	assert.expect( 1 );