Core: added .entries property to error thrown when duplicate stories are present

code/lib/core-server/src/utils/StoryIndexGenerator.test.ts

@@ -8,12 +8,12 @@
 import path from 'path';
 import fs from 'fs-extra';
 import { normalizeStoriesEntry } from '@storybook/core-common';
-import type { NormalizedStoriesSpecifier, StoryIndexer } from '@storybook/types';
+import type { NormalizedStoriesSpecifier, StoryIndexer, StoryIndexEntry } from '@storybook/types';
 import { loadCsf, getStorySortParameter } from '@storybook/csf-tools';
 import { toId } from '@storybook/csf';
 import { logger } from '@storybook/node-logger';
 
-import { StoryIndexGenerator } from './StoryIndexGenerator';
+import { StoryIndexGenerator, DuplicateEntriesError } from './StoryIndexGenerator';
 
 jest.mock('@storybook/csf-tools');
 jest.mock('@storybook/csf', () => {
@@ -902,6 +902,27 @@ describe('StoryIndexGenerator', () => {
           `"🚨 You have a story for A with the same name as your default docs entry name (Story One), so the docs page is being dropped. Consider changing the story name."`
         );
       });
+      it('warns when two duplicate stories exists, with duplicated entries details', async () => {
+        const generator = new StoryIndexGenerator([storiesSpecifier, docsSpecifier], {
+          ...options,
+        });
+        await generator.initialize();
+        const mockEntry: StoryIndexEntry = {
+          id: 'StoryId',
+          name: 'StoryName',
+          title: 'ComponentTitle',
+          importPath: 'Path',
+          type: 'story',
+        };
+        expect(() => {
+          generator.chooseDuplicate(mockEntry, mockEntry);
+        }).toThrow(
+          new DuplicateEntriesError(`Duplicate stories with id: ${mockEntry.id}`, [
+            mockEntry,
+            mockEntry,
+          ])
+        );
+      });
     });
   });
 

code/lib/core-server/src/utils/StoryIndexGenerator.ts

@@ -37,6 +37,16 @@ type StoriesCacheEntry = {
 type CacheEntry = false | StoriesCacheEntry | DocsCacheEntry;
 type SpecifierStoriesCache = Record<Path, CacheEntry>;
 
+export class DuplicateEntriesError extends Error {
+  entries: IndexEntry[];
+
+  constructor(message: string, entries: IndexEntry[]) {
+    super();
+    this.message = message;
+    this.entries = entries;
+  }
+}
+
 const makeAbsolute = (otherImport: Path, normalizedPath: Path, workingDir: Path) =>
   otherImport.startsWith('.')
     ? slash(
@@ -352,7 +362,11 @@ export class StoryIndexGenerator {
     const changeDocsName = 'Use `<Meta of={} name="Other Name">` to distinguish them.';
 
     // This shouldn't be possible, but double check and use for typing
-    if (worseEntry.type === 'story') throw new Error(`Duplicate stories with id: ${firstEntry.id}`);
+    if (worseEntry.type === 'story')
+      throw new DuplicateEntriesError(`Duplicate stories with id: ${firstEntry.id}`, [
+        firstEntry,
+        secondEntry,
+      ]);
 
     if (betterEntry.type === 'story') {
       const worseDescriptor = worseEntry.standalone