From 33807c08b666d93d65fc010cb422a1559d520575 Mon Sep 17 00:00:00 2001
From: =?utf8?q?Bartosz=20Dziewo=C5=84ski?= <matma.rex@gmail.com>
Date: Tue, 17 Apr 2018 15:05:05 +0200
Subject: [PATCH] mw.widgets.UsersMultiselectWidget: Compat with
 mw.special.preferences.confirmClose

Replace `<input type="hidden">` with a `<textarea>` hidden using
`display: none`, because the former does not have separate 'value'
and 'defaultValue' properties, and the Special:Preferences script to
enable/disable the "Save" button depends on them to work correctly.
We use a similar approach in OOUI (RadioSelectInputWidget).

Also correct a code comment (we need to trigger a 'change' event for
any kind of input, not just `<input type="hidden">`).

Bug: T192147
Change-Id: I2351bc752f9cf25a607f4b197c132062d52ecb1e
---
 .../mw.widgets.UsersMultiselectWidget.js         | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/resources/src/mediawiki.widgets/mw.widgets.UsersMultiselectWidget.js b/resources/src/mediawiki.widgets/mw.widgets.UsersMultiselectWidget.js
index d250ad8533..f0ad0565d9 100644
--- a/resources/src/mediawiki.widgets/mw.widgets.UsersMultiselectWidget.js
+++ b/resources/src/mediawiki.widgets/mw.widgets.UsersMultiselectWidget.js
@@ -42,15 +42,17 @@
 		this.limit = config.limit;
 
 		if ( 'name' in config ) {
-			// If used inside HTML form, then create hidden input, which will store
-			// the results.
-			this.hiddenInput = $( '<input>' )
-				.attr( 'type', 'hidden' )
+			// Use this instead of <input type="hidden">, because hidden inputs do not have separate
+			// 'value' and 'defaultValue' properties. The script on Special:Preferences
+			// (mw.special.preferences.confirmClose) checks this property to see if a field was changed.
+			this.hiddenInput = $( '<textarea>' )
+				.addClass( 'oo-ui-element-hidden' )
 				.attr( 'name', config.name )
 				.appendTo( this.$element );
-
 			// Update with preset values
 			this.updateHiddenInput();
+			// Set the default value (it might be different from just being empty)
+			this.hiddenInput.prop( 'defaultValue', this.getSelectedUsernames().join( '\n' ) );
 		}
 
 		this.menu = this.getMenu();
@@ -152,8 +154,8 @@
 	mw.widgets.UsersMultiselectWidget.prototype.updateHiddenInput = function () {
 		if ( 'hiddenInput' in this ) {
 			this.hiddenInput.val( this.getSelectedUsernames().join( '\n' ) );
-			// Hidden inputs do not trigger onChange.
-			// @see https://developer.mozilla.org/en-US/docs/Web/HTML/Element/input/hidden
+			// Trigger a 'change' event as if a user edited the text
+			// (it is not triggered when changing the value from JS code).
 			this.hiddenInput.trigger( 'change' );
 		}
 	};
-- 
2.20.1