notice potential repeated children key entries immediately (#31898)

lib/create-tree.js

@@ -56,6 +56,7 @@ export default async function createTree(originalPath, langObj) {
 
   // Process frontmatter children recursively.
   if (item.page.children) {
+    assertUniqueChildren(item.page)
     item.childPages = (
       await Promise.all(
         item.page.children.map(
@@ -67,3 +68,15 @@ export default async function createTree(originalPath, langObj) {
 
   return item
 }
+
+function assertUniqueChildren(page) {
+  if (page.children.length !== new Set(page.children).size) {
+    const count = {}
+    page.children.forEach((entry) => (count[entry] = 1 + (count[entry] || 0)))
+    let msg = `${page.relativePath} has duplicates in the 'children' key.`
+    for (const [entry, times] of Object.entries(count)) {
+      if (times > 1) msg += ` '${entry}' is repeated ${times} times. `
+    }
+    throw new Error(msg)
+  }
+}

tests/unit/pages.js

@@ -1,6 +1,6 @@
 import { jest } from '@jest/globals'
 import path from 'path'
-import { loadPages, loadPageMap, correctTranslationOrphans } from '../../lib/page-data.js'
+import { loadPages, correctTranslationOrphans } from '../../lib/page-data.js'
 import libLanguages from '../../lib/languages.js'
 import { liquid } from '../../lib/render-content/index.js'
 import patterns from '../../lib/patterns.js'
@@ -152,29 +152,4 @@ describe('pages module', () => {
       expect(liquidErrors.length, failureMessage).toBe(0)
     })
   })
-
-  describe('loadPageMap', () => {
-    let pageMap
-    beforeAll(async () => {
-      pageMap = await loadPageMap(pages)
-    })
-
-    test('yields a non-empty object with more unique entries than pages', async () => {
-      // Why does it contain MORE unique entries, you ask?
-      // TL;DR: The pages array contains one item per Page + language, with a `permalinks` array
-      // property for each product version supported (free-pro-team, enterprise-server@3.0, etc.)
-      // The pageMap, on the other hand, is keyed by unique URLs, so it has 1-N (where N is the
-      // number of product versions supported) keys pointing to the same Page + language object
-
-      expect(Array.isArray(pageMap)).toBe(false)
-      expect(Object.keys(pageMap).length).toBeGreaterThan(pages.length)
-    })
-
-    test('has an identical key list to the deep permalinks of the array', async () => {
-      const allPermalinks = pages.flatMap((page) => page.permalinks.map((pl) => pl.href)).sort()
-      const allPageUrls = Object.keys(pageMap).sort()
-
-      expect(allPageUrls).toEqual(allPermalinks)
-    })
-  })
 })