frontend/src/components/TopNav.tsx

@@ -123,7 +123,7 @@ export default (({ user }: Props) => {
 	const wikiPage = await fetchWikiPage (String (wikiId ?? ''), { })
 	const tag = await fetchTagByName (wikiPage.title)
 
-	setPostCount (tag.postCount)
+	setPostCount (tag?.postCount ?? 0)
       }
       catch
       {

frontend/src/components/WikiBody.tsx

@@ -1,18 +1,18 @@
-import { useEffect, useMemo, useState } from 'react'
+import { useQuery } from '@tanstack/react-query'
+import { useMemo } from 'react'
 import ReactMarkdown from 'react-markdown'
 import remarkGFM from 'remark-gfm'
 
 import PrefetchLink from '@/components/PrefetchLink'
 import SectionTitle from '@/components/common/SectionTitle'
 import SubsectionTitle from '@/components/common/SubsectionTitle'
-import { apiGet } from '@/lib/api'
+import { wikiKeys } from '@/lib/queryKeys'
 import remarkWikiAutoLink from '@/lib/remark-wiki-autolink'
+import { fetchWikiPages } from '@/lib/wiki'
 
 import type { FC } from 'react'
 import type { Components } from 'react-markdown'
 
-import type { WikiPage } from '@/types'
-
 type Props = { title: string
 	       body?: string }
 
@@ -32,25 +32,15 @@ const mdComponents = { h1:  ({ children }) => <SectionTitle>{children}</SectionT
 
 
 export default (({ title, body }: Props) => {
-  const [pageNames, setPageNames] = useState<string[]> ([])
+  const { data } = useQuery ({
+      enabled: Boolean (body),
+      queryKey: wikiKeys.index ({ }),
+      queryFn: () => fetchWikiPages ({ }) })
+  const pageNames = (data ?? []).map (page => page.title).sort ((a, b) => b.length - a.length)
 
   const remarkPlugins = useMemo (
       () => [() => remarkWikiAutoLink (pageNames), remarkGFM], [pageNames])
 
-  useEffect (() => {
-    void (async () => {
-      try
-      {
-	const data = await apiGet<WikiPage[]> ('/wiki')
-	setPageNames (data.map (page => page.title).sort ((a, b) => b.length - a.length))
-      }
-      catch
-      {
-	setPageNames ([])
-      }
-    }) ()
-  }, [])
-
   return (
       <ReactMarkdown components={mdComponents} remarkPlugins={remarkPlugins}>
 	{body || `このページは存在しません。[新規作成してください](/wiki/new?title=${ encodeURIComponent (title) })。`}

frontend/src/lib/prefetchers.ts

@@ -31,31 +31,20 @@ const prefetchWikiPageShow: Prefetcher = async (qc, url) => {
 
   const wikiPage = await qc.fetchQuery ({
       queryKey: wikiKeys.show (title, { version }),
-      queryFn:  async () => {
-	try
-	{
-	  return await fetchWikiPageByTitle (title, { version })
-	}
-	catch
-	{
-	  return null
-	}
-      } })
+      queryFn:  () => fetchWikiPageByTitle (title, { version }) })
+
+  if (wikiPage?.body)
+    {
+      await qc.prefetchQuery ({
+	  queryKey: wikiKeys.index ({ }),
+	  queryFn: () => fetchWikiPages ({ }) })
+    }
 
   const effectiveTitle = wikiPage?.title ?? title
 
   await qc.prefetchQuery ({
       queryKey: tagsKeys.show (effectiveTitle),
-      queryFn:  async () => { 
-	try
-	{
-	  return await fetchTagByName (effectiveTitle)
-	}
-	catch
-	{
-	  return null
-	}
-      } })
+      queryFn: () => fetchTagByName (effectiveTitle) })
 
   if (version)
     return

frontend/src/lib/queryKeys.ts

@@ -13,5 +13,5 @@ export const tagsKeys = {
 
 export const wikiKeys = {
     root:   ['wiki'] as const,
-    index:  (p: { title: string }) => ['wiki', 'index', p] as const,
+    index:  (p: { title?: string }) => ['wiki', 'index', p] as const,
     show:   (title: string, p: { version?: string }) => ['wiki', title, p] as const }

frontend/src/lib/tags.ts

@@ -3,5 +3,13 @@ import { apiGet } from '@/lib/api'
 import type { Tag } from '@/types'
 
 
-export const fetchTagByName = async (name: string): Promise<Tag> =>
-    await apiGet (`/tags/name/${ name }`)
+export const fetchTagByName = async (name: string): Promise<Tag | null> => {
+  try
+  {
+    return await apiGet (`/tags/name/${ name }`)
+  }
+  catch
+  {
+    return null
+  }
+}

frontend/src/lib/wiki.ts

@@ -3,7 +3,9 @@ import { apiGet } from '@/lib/api'
 import type { WikiPage } from '@/types'
 
 
-export const fetchWikiPages = async ({ title }: { title: string }) =>
+export const fetchWikiPages = async (
+    { title }:  { title?: string },
+): Promise<WikiPage[]> =>
     await apiGet ('/wiki', { params: { title } })
 
 
@@ -17,6 +19,13 @@ export const fetchWikiPage = async (
 export const fetchWikiPageByTitle = async (
     title:        string,
     { version }:  { version?: string },
-): Promise<WikiPage> =>
-    await apiGet (`/wiki/title/${ title }`,
-		  { params: version ? { version } : { } })
+): Promise<WikiPage | null> => {
+  try
+  {
+    return await apiGet (`/wiki/title/${ title }`, { params: { version } })
+  }
+  catch
+  {
+    return null
+  }
+}