minimize content in miniToc prop (#28522)

* make miniToc pure data and no html strings

* fixups

* minimize content in miniToc prop

* minimize content in miniToc prop

* some types refactoring

* fix tests

components/context/ArticleContext.tsx

@@ -8,7 +8,7 @@ export type LearningTrack = {
 }
 
 export type MiniTocItem = {
-  platform: string
+  platform?: string
   contents: {
     href: string
     title: string

lib/get-mini-toc-items.js

@@ -1,12 +1,7 @@
 import cheerio from 'cheerio'
 import { range } from 'lodash-es'
 
-export default function getMiniTocItems(
+export default function getMiniTocItems(html, maxHeadingLevel = 2, headingScope = '') {
-  html,
-  maxHeadingLevel = 2,
-  headingScope = '',
-  isRestPage = false
-) {
   const $ = cheerio.load(html, { xmlMode: true })
 
   // eg `h2, h3` or `h2, h3, h4` depending on maxHeadingLevel
@@ -67,7 +62,7 @@ export default function getMiniTocItems(
   // convert the flatToc to a nested structure to simplify semantic rendering on the client
   const nestedToc = buildNestedToc(flatToc)
 
-  return nestedToc
+  return minimalMiniToc(nestedToc)
 }
 
 // Recursively build a tree from the list of allItems
@@ -116,3 +111,15 @@ function buildNestedToc(allItems, startIndex = 0) {
 
   return currentLevel
 }
+
+// Strip the bits and pieces from each object in the array that are
+// not needed in the React component rendering.
+function minimalMiniToc(toc) {
+  return toc.map(({ platform, contents, items }) => {
+    const minimal = { contents }
+    const subItems = minimalMiniToc(items)
+    if (subItems.length) minimal.items = subItems
+    if (platform) minimal.platform = platform
+    return minimal
+  })
+}

tests/unit/mini-toc-items.js

@@ -63,7 +63,7 @@ describe('mini toc items', () => {
     `
     const tocItems = getMiniTocItems(html, 3)
     expect(tocItems.length).toBe(2)
-    expect(tocItems[0].items.length).toBe(0)
+    expect(tocItems[0].items).toBeUndefined()
   })
 
   test('handles deeply nested toc', async () => {