Improve Explorer welcome view (fix microsoft#137414) (microsoft#137475)

* Improve Explorer welcome view (fix microsoft#137414)

* don't duplicate noFolder welcome help in the IsWebContext case

* simplify noFolderHelp when-clauses

Author: gjsjohnmurray

src/vs/workbench/contrib/files/browser/explorerViewlet.ts

@@ -298,10 +298,18 @@ viewsRegistry.registerViewWelcomeContent(EmptyView.ID, {
 	order: 1
 });
 
+viewsRegistry.registerViewWelcomeContent(EmptyView.ID, {
+	content: localize({ key: 'noFolderButEditorsHelp', comment: ['Please do not translate the word "commmand", it is part of our internal syntax which must not change'] },
+		"You have not yet opened a folder.\n[Open Folder](command:{0})\nOpening a folder will close all currently open editors. To keep them open, [add a folder](command:{1}) instead.", commandId, AddRootFolderAction.ID),
+	when: ContextKeyExpr.and(ContextKeyExpr.has('editorIsOpen'), ContextKeyExpr.or(ContextKeyExpr.and(WorkbenchStateContext.notEqualsTo('workspace'), RemoteNameContext.isEqualTo('')), ContextKeyExpr.and(WorkbenchStateContext.notEqualsTo('workspace'), IsWebContext))),
+	group: ViewContentGroups.Open,
+	order: 1
+});
+
 viewsRegistry.registerViewWelcomeContent(EmptyView.ID, {
 	content: localize({ key: 'noFolderHelp', comment: ['Please do not translate the word "commmand", it is part of our internal syntax which must not change'] },
 		"You have not yet opened a folder.\n[Open Folder](command:{0})", commandId),
-	when: ContextKeyExpr.or(ContextKeyExpr.and(WorkbenchStateContext.notEqualsTo('workspace'), RemoteNameContext.isEqualTo('')), ContextKeyExpr.and(WorkbenchStateContext.notEqualsTo('workspace'), IsWebContext)),
+	when: ContextKeyExpr.and(ContextKeyExpr.has('editorIsOpen')?.negate(), ContextKeyExpr.or(ContextKeyExpr.and(WorkbenchStateContext.notEqualsTo('workspace'), RemoteNameContext.isEqualTo('')), ContextKeyExpr.and(WorkbenchStateContext.notEqualsTo('workspace'), IsWebContext))),
 	group: ViewContentGroups.Open,
 	order: 1
 });