block: add regression test

regression test for wikimedia-gadgets#2106

modules/twinkleblock.js

@@ -1899,13 +1899,14 @@ Twinkle.block.callback.issue_template = function twinkleblockCallbackIssueTempla
 	// "talk page" of an IP range (which does not exist)
 	const userTalkPage = 'User_talk:' + mw.config.get('wgRelevantUserName');
 
-	const params = $.extend(formData, {
-		messageData: Twinkle.block.blockPresetsInfo[formData.template],
-		reason: Twinkle.block.field_template_options.block_reason,
-		disabletalk: Twinkle.block.field_template_options.notalk,
-		noemail: Twinkle.block.field_template_options.noemail_template,
-		nocreate: Twinkle.block.field_template_options.nocreate_template
-	});
+	const params = Twinkle.block.callback.combineFormDataAndFieldTemplateOptions(
+		formData,
+		Twinkle.block.blockPresetsInfo[formData.template],
+		Twinkle.block.field_template_options.block_reason,
+		Twinkle.block.field_template_options.notalk,
+		Twinkle.block.field_template_options.noemail_template,
+		Twinkle.block.field_template_options.nocreate_template
+	);
 
 	Morebits.wiki.actionCompleted.redirect = userTalkPage;
 	Morebits.wiki.actionCompleted.notice = 'Actions complete, loading user talk page in a few seconds';
@@ -1915,6 +1916,16 @@ Twinkle.block.callback.issue_template = function twinkleblockCallbackIssueTempla
 	wikipedia_page.load(Twinkle.block.callback.main);
 };
 
+Twinkle.block.callback.combineFormDataAndFieldTemplateOptions = function(formData, messageData, reason, disabletalk, noemail, nocreate) {
+	return $.extend(formData, {
+		messageData: messageData,
+		reason: reason,
+		disabletalk: disabletalk,
+		noemail: noemail,
+		nocreate: nocreate
+	});
+};
+
 Twinkle.block.callback.getBlockNoticeWikitext = function(params) {
 	let text = '{{', settings = Twinkle.block.blockPresetsInfo[params.template];
 	if (!settings.nonstandard) {

tests/jest.setup.js

@@ -6,6 +6,7 @@ mw.config.set({
 
 require('../morebits.js');
 require('../twinkle.js');
+require('../modules/twinkleblock.js');
 require('../modules/twinklewarn.js');
 require('../modules/twinklexfd.js');
 global.Morebits = window.Morebits;

tests/twinkleblock.test.js

@@ -0,0 +1,15 @@
+describe('modules/twinkleblock', () => {
+	describe('callback.combineFormDataAndFieldTemplateOptions', () => {
+		// https://github.com/wikimedia-gadgets/twinkle/issues/2106
+		test('regression test: merging true and undefined should return true', () => {
+			const formData = {disabletalk: true};
+			const messageData = undefined;
+			const reason = undefined;
+			const disabletalk = undefined;
+			const noemail = undefined;
+			const nocreate = undefined;
+			const expected = {disabletalk: true};
+			expect(Twinkle.block.callback.combineFormDataAndFieldTemplateOptions(formData, messageData, reason, disabletalk, noemail, nocreate)).toStrictEqual(expected);
+		});
+	});
+});