From a4421101fd6d9d7b0550210f8e8690641733dd9a Mon Sep 17 00:00:00 2001
From: =?utf8?q?Micha=C5=82=20Go=C5=82=C4=99biowski-Owczarek?=
 <m.goleb@gmail.com>
Date: Tue, 1 Sep 2020 10:42:03 +0200
Subject: [PATCH] Attributes: Drop the `toggleClass(boolean|undefined)`
 signature

The behavior of this signature is not intuitive, especially if classes are
manipulated via other ways between `toggleClass` calls.

Fixes gh-3388
Closes gh-4766
---
 src/attributes/classes.js | 56 ++++++++++-----------------------------
 test/unit/attributes.js   | 21 +--------------
 2 files changed, 15 insertions(+), 62 deletions(-)

diff --git a/src/attributes/classes.js b/src/attributes/classes.js
index dcd8ad059..796fbcc80 100644
--- a/src/attributes/classes.js
+++ b/src/attributes/classes.js
@@ -1,7 +1,6 @@
 import jQuery from "../core.js";
 import stripAndCollapse from "../core/stripAndCollapse.js";
 import rnothtmlwhite from "../var/rnothtmlwhite.js";
-import dataPriv from "../data/var/dataPriv.js";
 
 import "../core/init.js";
 
@@ -103,13 +102,6 @@ jQuery.fn.extend( {
 	},
 
 	toggleClass: function( value, stateVal ) {
-		var type = typeof value,
-			isValidValue = type === "string" || Array.isArray( value );
-
-		if ( typeof stateVal === "boolean" && isValidValue ) {
-			return stateVal ? this.addClass( value ) : this.removeClass( value );
-		}
-
 		if ( typeof value === "function" ) {
 			return this.each( function( i ) {
 				jQuery( this ).toggleClass(
@@ -119,45 +111,25 @@ jQuery.fn.extend( {
 			} );
 		}
 
+		if ( typeof stateVal === "boolean" ) {
+			return stateVal ? this.addClass( value ) : this.removeClass( value );
+		}
+
 		return this.each( function() {
 			var className, i, self, classNames;
 
-			if ( isValidValue ) {
-
-				// Toggle individual class names
-				i = 0;
-				self = jQuery( this );
-				classNames = classesToArray( value );
-
-				while ( ( className = classNames[ i++ ] ) ) {
-
-					// Check each className given, space separated list
-					if ( self.hasClass( className ) ) {
-						self.removeClass( className );
-					} else {
-						self.addClass( className );
-					}
-				}
-
-			// Toggle whole class name
-			} else if ( value === undefined || type === "boolean" ) {
-				className = getClass( this );
-				if ( className ) {
+			// Toggle individual class names
+			i = 0;
+			self = jQuery( this );
+			classNames = classesToArray( value );
 
-					// Store className if set
-					dataPriv.set( this, "__className__", className );
-				}
+			while ( ( className = classNames[ i++ ] ) ) {
 
-				// If the element has a class name or if we're passed `false`,
-				// then remove the whole classname (if there was one, the above saved it).
-				// Otherwise bring back whatever was previously saved (if anything),
-				// falling back to the empty string if nothing was stored.
-				if ( this.setAttribute ) {
-					this.setAttribute( "class",
-						className || value === false ?
-							"" :
-							dataPriv.get( this, "__className__" ) || ""
-					);
+				// Check each className given, space separated list
+				if ( self.hasClass( className ) ) {
+					self.removeClass( className );
+				} else {
+					self.addClass( className );
 				}
 			}
 		} );
diff --git a/test/unit/attributes.js b/test/unit/attributes.js
index 4b014bacc..d83375172 100644
--- a/test/unit/attributes.js
+++ b/test/unit/attributes.js
@@ -1415,7 +1415,7 @@ QUnit.test( "removeClass(undefined) is a no-op", function( assert ) {
 } );
 
 var testToggleClass = function( valueObj, assert ) {
-	assert.expect( 19 );
+	assert.expect( 11 );
 
 	var e = jQuery( "#firstp" );
 	assert.ok( !e.is( ".test" ), "Assert class not present" );
@@ -1443,25 +1443,6 @@ var testToggleClass = function( valueObj, assert ) {
 	assert.ok( ( e.is( ".testA.testC" ) && !e.is( ".testB" ) ), "Assert 1 class added, 1 class removed, and 1 class kept" );
 	e.toggleClass( valueObj( "testA testC" ) );
 	assert.ok( ( !e.is( ".testA" ) && !e.is( ".testB" ) && !e.is( ".testC" ) ), "Assert no class present" );
-
-	// toggleClass storage
-	e.toggleClass( true );
-	assert.ok( e[ 0 ].className === "", "Assert class is empty (data was empty)" );
-	e.addClass( "testD testE" );
-	assert.ok( e.is( ".testD.testE" ), "Assert class present" );
-	e.toggleClass();
-	assert.ok( !e.is( ".testD.testE" ), "Assert class not present" );
-	assert.ok( jQuery._data( e[ 0 ], "__className__" ) === "testD testE", "Assert data was stored" );
-	e.toggleClass();
-	assert.ok( e.is( ".testD.testE" ), "Assert class present (restored from data)" );
-	e.toggleClass( false );
-	assert.ok( !e.is( ".testD.testE" ), "Assert class not present" );
-	e.toggleClass( true );
-	assert.ok( e.is( ".testD.testE" ), "Assert class present (restored from data)" );
-	e.toggleClass();
-	e.toggleClass( false );
-	e.toggleClass();
-	assert.ok( e.is( ".testD.testE" ), "Assert class present (restored from data)" );
 };
 
 QUnit.test( "toggleClass(String|boolean|undefined[, boolean])", function( assert ) {
-- 
2.39.5