[FIX] LocatorResourcePool: Wait for resources in prepare step (#719)

Issue was introduced with #695.

lib/lbt/resources/LocatorResourcePool.js

@@ -10,7 +10,7 @@ class LocatorResourcePool extends ResourcePool {
 				if (!moduleName) {
 					moduleName = resource.getPath().slice("/resources/".length);
 				}
-				this.addResource(new LocatorResource(this, resource, moduleName));
+				return this.addResource(new LocatorResource(this, resource, moduleName));
 			}).filter(Boolean)
 		);
 	}

test/lib/lbt/resources/LocatorResourcePool.js

@@ -1,8 +1,24 @@
 const test = require("ava");
 const LocatorResourcePool = require("../../../../lib/lbt/resources/LocatorResourcePool");
+const Resource = require("@ui5/fs").Resource;
 
 test("getIgnoreMissingModules", async (t) => {
 	const resourcePool = new LocatorResourcePool({ignoreMissingModules: true});
 	t.true(resourcePool.getIgnoreMissingModules(), "ignoreMissingModules is true");
 });
 
+test("wait for resources to finish prepare", async (t) => {
+	let promiseResolved = false;
+	const promise = new Promise((resolve) => {
+		setTimeout(() => {
+			promiseResolved = true;
+			resolve();
+		}, 10);
+	});
+	const resourcePool = new LocatorResourcePool();
+	resourcePool.addResource = () => promise;
+	return resourcePool.prepare([new Resource({path: "mypath"})]).then(() => {
+		t.true(promiseResolved, "addResources promise is resolved before prepare promise is resolved");
+	});
+});
+