Blueprints: Support a landingPage value without the initial slash (#1227

)

Without this PR, a Blueprint like `{ "landingPage":
"wp-admin/plugins.php" }` won't work as there is no initial slash. This
PR adjusts the Playground API to prepend that slash as URLs without one
should be relative to the document root anyway.

 ## Testing instructions

Confirm the E2E tests passed

cc @bph  @dmsnell

packages/playground/remote/src/lib/boot-playground-remote.ts

@@ -130,6 +130,9 @@ export async function bootPlaygroundRemote() {
 			});
 		},
 		async goTo(requestedPath: string) {
+			if (!requestedPath.startsWith('/')) {
+				requestedPath = '/' + requestedPath;
+			}
 			/**
 			 * People often forget to type the trailing slash at the end of
 			 * /wp-admin/ URL and end up with wrong relative hrefs. Let's

packages/playground/website/cypress/e2e/blueprints.cy.ts

@@ -33,6 +33,15 @@ describe('Blueprints', () => {
 		cy.wordPressDocument().its('body').should('contain', 'Sample Page');
 	});
 
+	it('Landing page without the initial slash should work', () => {
+		const blueprint: Blueprint = {
+			landingPage: 'wp-admin/plugins.php',
+			login: true,
+		};
+		cy.visit('/#' + JSON.stringify(blueprint));
+		cy.wordPressDocument().its('body').should('contain.text', 'Plugins');
+	});
+
 	it('enableMultisite step should enable a multisite', () => {
 		const blueprint: Blueprint = {
 			landingPage: '/',