fix(mcp): list reporting tabs for an unknown NgRx page

packages/devtools/src/rpc/__tests__/ngrx-live-tools.test.ts

@@ -306,3 +306,47 @@ describe('withUntrustedPreamble', () => {
     expect(text.length).toBeLessThanOrEqual(NGRX_LIVE_TOOL_MAX + 200);
   });
 });
+
+describe('an unknown page', () => {
+  function twoPages(): NgrxPages {
+    const pages: NgrxPages = new Map();
+    for (const [pid, at] of [
+      ['p1', 1_000],
+      ['p2', 2_000],
+    ] as const) {
+      mergeNgrxReport(
+        pages,
+        {
+          pageId: pid,
+          session: 's',
+          url: `/${pid}`,
+          title: '',
+          stores: [store()],
+          classic: null,
+          log: [logEntry({ seq: 1 })],
+        },
+        [],
+        at,
+      );
+    }
+    return pages;
+  }
+
+  const tools = [
+    ['inspect-signal-store', (pages: NgrxPages) => inspectSignalStoreText(pages, 'p3')],
+    ['signal-store-history', (pages: NgrxPages) => signalStoreHistoryText(pages, 'p3')],
+  ] as const;
+
+  for (const [name, answer] of tools) {
+    it(`${name} lists the pages that do report, newest first`, () => {
+      const text = answer(twoPages());
+      expect(text).toContain('No page `p3` is reporting NgRx state.');
+      expect(text).toMatch(/`p2`.*`p1`/);
+      expect(text).not.toMatch(/no ngrx state has been reported/i);
+    });
+
+    it(`${name} still says nothing was reported when no page reports`, () => {
+      expect(answer(new Map())).toMatch(/no ngrx state has been reported/i);
+    });
+  }
+});

packages/devtools/src/rpc/ngrx-live-tools.ts

@@ -1,5 +1,6 @@
 import type { NgrxPageRecord, NgrxPages } from './ngrx-tools.ts';
 import type { NgrxLogEntry, NgrxSignalStoreInfo } from '../ngrx-shared.ts';
+import { unknownPageText } from './pages.ts';
 
 /**
  * `inspectSignalStoreText`/`signalStoreHistoryText` output is capped to this
@@ -26,6 +27,15 @@ function pagesOf(pages: NgrxPages, pageId?: string): NgrxPageRecord[] {
   return pageId ? all.filter((p) => p.pageId === pageId) : all;
 }
 
+/**
+ * The answer when no page matches. An unknown `page` lists the tabs that do report
+ * NgRx state, like the other page tools; with no tab reporting at all it is `NO_DATA`.
+ */
+function noMatchText(pages: NgrxPages, pageId?: string): string {
+  if (pageId && pages.size) return unknownPageText(pageId, [...pages.values()], 'NgRx state');
+  return pageId ? `No page ${code(pageId)} is reporting NgRx state.\n\n${NO_DATA}` : NO_DATA;
+}
+
 function storeLabel(store: NgrxSignalStoreInfo): string {
   return store.name ?? store.className;
 }
@@ -119,9 +129,7 @@ export function inspectSignalStoreText(
   storeId?: string,
 ): string {
   const matching = pagesOf(pages, pageId);
-  if (!matching.length) {
-    return pageId ? `No page ${code(pageId)} is reporting NgRx state.\n\n${NO_DATA}` : NO_DATA;
-  }
+  if (!matching.length) return noMatchText(pages, pageId);
   if (storeId) {
     for (const page of matching) {
       const store = page.stores.find((s) => s.id === storeId);
@@ -181,9 +189,7 @@ export function signalStoreHistoryText(
   since?: number,
 ): string {
   const matching = pagesOf(pages, pageId);
-  if (!matching.length) {
-    return pageId ? `No page ${code(pageId)} is reporting NgRx state.\n\n${NO_DATA}` : NO_DATA;
-  }
+  if (!matching.length) return noMatchText(pages, pageId);
   if (typeof since === 'number' && matching.length > 1) {
     return `Pass \`page\` to identify a single page when using \`since\`; sequence numbers are per-page and cannot be compared across pages.`;
   }