From f7e9cfeb3a06ec93726870dd17116a019959d980 Mon Sep 17 00:00:00 2001
From: Divyansh Singh <40380293+brc-dd@users.noreply.github.com>
Date: Wed, 13 Jul 2022 22:49:06 +0530
Subject: [PATCH] fix: de-duplicate head tags while merging (#975) (#976)

---
 src/client/app/composables/head.ts | 50 ++++++------------------------
 src/node/build/render.ts           | 16 +++++++---
 src/node/config.ts                 |  2 +-
 src/shared/shared.ts               | 20 +++++++++++-
 4 files changed, 40 insertions(+), 48 deletions(-)

diff --git a/src/client/app/composables/head.ts b/src/client/app/composables/head.ts
index 91a46d217fb..d74d6b5c0af 100644
--- a/src/client/app/composables/head.ts
+++ b/src/client/app/composables/head.ts
@@ -1,5 +1,5 @@
 import { watchEffect, Ref } from 'vue'
-import { HeadConfig, SiteData, createTitle } from '../../shared'
+import { HeadConfig, SiteData, createTitle, mergeHead } from '../../shared'
 import { Route } from '../router'
 
 export function useUpdateHead(route: Route, siteDataByRouteRef: Ref<SiteData>) {
@@ -14,50 +14,20 @@ export function useUpdateHead(route: Route, siteDataByRouteRef: Ref<SiteData>) {
       return
     }
 
-    const newEls: HTMLElement[] = []
-    const commonLength = Math.min(managedHeadTags.length, newTags.length)
-    for (let i = 0; i < commonLength; i++) {
-      let el = managedHeadTags[i]
-      const [tag, attrs, innerHTML = ''] = newTags[i]
-      if (el.tagName.toLocaleLowerCase() === tag) {
-        for (const key in attrs) {
-          if (el.getAttribute(key) !== attrs[key]) {
-            el.setAttribute(key, attrs[key])
-          }
-        }
-        for (let i = 0; i < el.attributes.length; i++) {
-          const name = el.attributes[i].name
-          if (!(name in attrs)) {
-            el.removeAttribute(name)
-          }
-        }
-        if (el.innerHTML !== innerHTML) {
-          el.innerHTML = innerHTML
-        }
-      } else {
-        document.head.removeChild(el)
-        el = createHeadElement(newTags[i])
-        document.head.append(el)
-      }
-      newEls.push(el)
-    }
-
-    managedHeadTags
-      .slice(commonLength)
-      .forEach((el) => document.head.removeChild(el))
-    newTags.slice(commonLength).forEach((headConfig) => {
+    managedHeadTags.forEach((el) => document.head.removeChild(el))
+    managedHeadTags = []
+    newTags.forEach((headConfig) => {
       const el = createHeadElement(headConfig)
       document.head.appendChild(el)
-      newEls.push(el)
+      managedHeadTags.push(el)
     })
-    managedHeadTags = newEls
   }
 
   watchEffect(() => {
     const pageData = route.data
     const siteData = siteDataByRouteRef.value
     const pageDescription = pageData && pageData.description
-    const frontmatterHead = pageData && pageData.frontmatter.head
+    const frontmatterHead = (pageData && pageData.frontmatter.head) || []
 
     // update title and description
     document.title = createTitle(siteData, pageData)
@@ -66,11 +36,9 @@ export function useUpdateHead(route: Route, siteDataByRouteRef: Ref<SiteData>) {
       .querySelector(`meta[name=description]`)!
       .setAttribute('content', pageDescription || siteData.description)
 
-    updateHeadTags([
-      // site head can only change during dev
-      ...(import.meta.env.DEV ? siteData.head : []),
-      ...(frontmatterHead ? filterOutHeadDescription(frontmatterHead) : [])
-    ])
+    updateHeadTags(
+      mergeHead(siteData.head, filterOutHeadDescription(frontmatterHead))
+    )
   })
 }
 
diff --git a/src/node/build/render.ts b/src/node/build/render.ts
index c4330e3e63a..a03729e5f42 100644
--- a/src/node/build/render.ts
+++ b/src/node/build/render.ts
@@ -5,7 +5,13 @@ import { pathToFileURL } from 'url'
 import escape from 'escape-html'
 import { normalizePath, transformWithEsbuild } from 'vite'
 import { RollupOutput, OutputChunk, OutputAsset } from 'rollup'
-import { HeadConfig, PageData, createTitle, notFoundPageData } from '../shared'
+import {
+  HeadConfig,
+  PageData,
+  createTitle,
+  notFoundPageData,
+  mergeHead
+} from '../shared'
 import { slash } from '../utils/slash'
 import { SiteConfig, resolveSiteDataByRoute } from '../config'
 
@@ -115,10 +121,10 @@ export async function renderPage(
   const title: string = createTitle(siteData, pageData)
   const description: string = pageData.description || siteData.description
 
-  const head = [
-    ...siteData.head,
-    ...filterOutHeadDescription(pageData.frontmatter.head)
-  ]
+  const head = mergeHead(
+    siteData.head,
+    filterOutHeadDescription(pageData.frontmatter.head)
+  )
 
   let inlinedScript = ''
   if (config.mpa && result) {
diff --git a/src/node/config.ts b/src/node/config.ts
index 223238c72e5..1fac1d1b083 100644
--- a/src/node/config.ts
+++ b/src/node/config.ts
@@ -285,7 +285,7 @@ function resolveSiteDataHead(userConfig?: UserConfig): HeadConfig[] {
   if (userConfig?.appearance ?? true) {
     head.push([
       'script',
-      {},
+      { id: 'check-dark-light' },
       `
         ;(() => {
           const saved = localStorage.getItem('${APPEARANCE_KEY}')
diff --git a/src/shared/shared.ts b/src/shared/shared.ts
index 67cb0b942df..e5041629858 100644
--- a/src/shared/shared.ts
+++ b/src/shared/shared.ts
@@ -1,4 +1,9 @@
-import { SiteData, PageData, LocaleConfig } from '../../types/shared'
+import {
+  SiteData,
+  PageData,
+  LocaleConfig,
+  HeadConfig
+} from '../../types/shared'
 
 export type {
   SiteData,
@@ -136,3 +141,16 @@ function cleanRoute(siteData: SiteData, route: string): string {
 
   return route.slice(baseWithoutSuffix.length)
 }
+
+function hasTag(head: HeadConfig[], tag: HeadConfig) {
+  const [tagType, tagAttrs] = tag
+  const keyAttr = Object.entries(tagAttrs)[0] // First key
+  if (keyAttr == null) return false
+  return head.some(
+    ([type, attrs]) => type === tagType && attrs[keyAttr[0]] === keyAttr[1]
+  )
+}
+
+export function mergeHead(prev: HeadConfig[], curr: HeadConfig[]) {
+  return [...prev.filter((tagAttrs) => !hasTag(curr, tagAttrs)), ...curr]
+}