Improve messaging for when a template is not found

Bug: T290140
Change-Id: Ie43c7e2bd72ed92a8a336f6d87a54e6d51cc3f17

extension.json

@@ -2227,6 +2227,9 @@
 				"visualeditor-dialog-transclusion-no-template-data-description",
 				"visualeditor-dialog-transclusion-no-template-description",
 				"visualeditor-dialog-transclusion-absent-template",
+				"visualeditor-dialog-transclusion-template-title-nonexistent",
+				"visualeditor-dialog-transclusion-template-title-modifier",
+				"visualeditor-dialog-transclusion-template-title-invalid",
 				"visualeditor-dialog-transclusion-options",
 				"visualeditor-dialog-transclusion-param-default",
 				"visualeditor-dialog-transclusion-param-example",

i18n/ve-mw/en.json

@@ -171,6 +171,9 @@
 	"visualeditor-dialog-template-title": "Template",
 	"visualeditor-dialog-transclusion-action-save": "Save",
 	"visualeditor-dialog-transclusion-absent-template": "The \"$1\" template doesn't yet exist.",
+	"visualeditor-dialog-transclusion-template-title-nonexistent": "This template doesn't exist.",
+	"visualeditor-dialog-transclusion-template-title-modifier": "Template documentation and [//www.mediawiki.org/wiki/Manual:Glossary#Parameter parameter] names (if existing) are not available when editing templates using modifiers, such as [//www.mediawiki.org/wiki/Help:Substitution subst].",
+	"visualeditor-dialog-transclusion-template-title-invalid": "This template can not exist since its name is invalid.",
 	"visualeditor-dialog-transclusion-add-content": "Add content",
 	"visualeditor-dialog-transclusion-add-wikitext": "Add wikitext",
 	"visualeditor-dialog-transclusion-add-param": "Add more information",

i18n/ve-mw/qqq.json

@@ -189,6 +189,9 @@
 	"visualeditor-dialog-template-title": "{{Identical|Template}}",
 	"visualeditor-dialog-transclusion-action-save": "Label for button that saves changes when editing an existing transclusion in the transclusion dialog.",
 	"visualeditor-dialog-transclusion-absent-template": "Message to user that the template they have selected does not exist on this wiki.\n\nParameters:\n* $1 - The title of the template.",
+	"visualeditor-dialog-transclusion-template-title-nonexistent": "Message to user that the template name they have provided does not exist on this wiki.",
+	"visualeditor-dialog-transclusion-template-title-modifier": "Message to user that the template name they have provided contains a modifier.",
+	"visualeditor-dialog-transclusion-template-title-invalid": "Message to user that the template name they have provided is invalid.",
 	"visualeditor-dialog-transclusion-add-content": "Label for button that adds parameter content to a transclusion.",
 	"visualeditor-dialog-transclusion-add-wikitext": "Label for button that adds parameter wikitext to a transclusion.",
 	"visualeditor-dialog-transclusion-add-param": "Label for button that adds a parameter to a transcluded template.",

modules/ve-mw/ui/pages/ve.ui.MWTemplatePage.js

@@ -67,12 +67,24 @@ ve.ui.MWTemplatePage = function VeUiMWTemplatePage( template, name, config ) {
 						)
 				);
 		} else if ( pageMissing ) {
+			var msg,
+				templateLabel = this.spec.getLabel();
+
+			if ( veConfig.transclusionDialogNewSidebar ) {
+				msg = mw.message(
+					templateLabel.match( /:/ ) ?
+						'visualeditor-dialog-transclusion-template-title-modifier' :
+						'visualeditor-dialog-transclusion-template-title-nonexistent'
+				);
+			} else {
+				msg = mw.message(
+					'visualeditor-dialog-transclusion-absent-template',
+					templateLabel
+				);
+			}
 			this.$description
 				.addClass( 've-ui-mwTemplatePage-description-missing' )
-				.append( mw.message(
+				.append( msg.parseDom() );
-					'visualeditor-dialog-transclusion-absent-template',
-					this.spec.getLabel()
-				).parseDom() );
 		} else if ( !veConfig.transclusionDialogNewSidebar || this.spec.isDocumented() ) {
 			this.$description
 				.addClass( 've-ui-mwTemplatePage-description-missing' )
@@ -82,6 +94,10 @@ ve.ui.MWTemplatePage = function VeUiMWTemplatePage( template, name, config ) {
 				).parseDom() );
 		}
 		ve.targetLinksToNewWindow( this.$description[ 0 ] );
+	} else if ( veConfig.transclusionDialogNewSidebar ) {
+		this.$description
+			.addClass( 've-ui-mwTemplatePage-description-missing' )
+			.append( mw.message( 'visualeditor-dialog-transclusion-template-title-invalid' ).parseDom() );
 	}
 	this.$description.find( 'a[href]' )
 		.on( 'click', function () {