fix(dashboards): enforce non-empty dashboardNamePrefix (#166)

We currently have this logic in the internal extension library, but this should be enforced at the core library level.

---

_By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license_

Author: Eugene Cheung

lib/dashboard/DefaultDashboardFactory.ts

@@ -96,6 +96,18 @@ export class DefaultDashboardFactory
   constructor(scope: Construct, id: string, props: MonitoringDashboardsProps) {
     super(scope, id);
 
+    const createDashboard = props.createDashboard ?? true;
+    const createSummaryDashboard = props.createSummaryDashboard ?? false;
+    const createAlarmDashboard = props.createAlarmDashboard ?? false;
+    const shouldCreateDashboards =
+      createDashboard || createAlarmDashboard || createSummaryDashboard;
+
+    if (shouldCreateDashboards && !props.dashboardNamePrefix) {
+      throw Error(
+        "A non-empty dashboardNamePrefix is required if dashboards are being created"
+      );
+    }
+
     const renderingPreference =
       props.renderingPreference ??
       DashboardRenderingPreference.INTERACTIVE_ONLY;
@@ -105,7 +117,7 @@ export class DefaultDashboardFactory
       "-" + (props.summaryDashboardRange ?? Duration.days(14)).toIsoString();
     let anyDashboardCreated = false;
 
-    if (props.createDashboard ?? true) {
+    if (createDashboard) {
       anyDashboardCreated = true;
       this.dashboard = this.createDashboard(renderingPreference, "Dashboard", {
         dashboardName: props.dashboardNamePrefix,
@@ -114,7 +126,7 @@ export class DefaultDashboardFactory
           props.detailDashboardPeriodOverride ?? PeriodOverride.INHERIT,
       });
     }
-    if (props.createSummaryDashboard ?? false) {
+    if (createSummaryDashboard) {
       anyDashboardCreated = true;
       this.summaryDashboard = this.createDashboard(
         renderingPreference,
@@ -127,7 +139,7 @@ export class DefaultDashboardFactory
         }
       );
     }
-    if (props.createAlarmDashboard ?? false) {
+    if (createAlarmDashboard) {
       anyDashboardCreated = true;
       this.alarmDashboard = this.createDashboard(
         renderingPreference,

test/dashboard/DefaultDashboardFactory.test.ts

@@ -11,6 +11,17 @@ import {
 test("default dashboards created", () => {
   const stack = new Stack();
 
+  new DefaultDashboardFactory(stack, "Dashboards", {
+    dashboardNamePrefix: "DummyDashboard",
+    renderingPreference: DashboardRenderingPreference.INTERACTIVE_ONLY,
+  });
+
+  expect(Template.fromStack(stack)).toMatchSnapshot();
+});
+
+test("all dashboards created", () => {
+  const stack = new Stack();
+
   new DefaultDashboardFactory(stack, "Dashboards", {
     dashboardNamePrefix: "DummyDashboard",
     createDashboard: true,
@@ -41,3 +52,17 @@ test("no dashboards created", () => {
 
   expect(Template.fromStack(stack)).toMatchSnapshot();
 });
+
+test("throws error if an empty dashboardNamePrefix is passed but dashboard are to be created", () => {
+  const stack = new Stack();
+
+  expect(() => {
+    new DefaultDashboardFactory(stack, "Dashboards", {
+      dashboardNamePrefix: "",
+      createDashboard: true,
+      renderingPreference: DashboardRenderingPreference.INTERACTIVE_ONLY,
+    });
+  }).toThrow(
+    "A non-empty dashboardNamePrefix is required if dashboards are being created"
+  );
+});