add redirect_from conflict validation

Author: LadyBluenotes

src/routes/blog.$.tsx

@@ -21,22 +21,35 @@ import { RecentPostsWidget } from '~/components/RecentPostsWidget'
 import { Toc } from '~/components/Toc'
 import { Breadcrumbs } from '~/components/Breadcrumbs'
 import { renderMarkdown } from '~/utils/markdown'
+import { buildRedirectManifest } from '~/utils/redirects'
 
 function handleRedirects(docsPath: string) {
+  const redirectEntries = allPosts.flatMap((post) =>
+    (post.redirectFrom ?? []).map((redirectFrom) => ({
+      from: normalizeBlogRedirectPath(redirectFrom),
+      to: post.slug,
+      source: post._meta.filePath,
+    })),
+  )
+  const redirectOwners = buildRedirectManifest(redirectEntries, {
+    label: 'blog posts',
+    formatTarget: (target) => `/blog/${target}`,
+  })
+
   const normalizedPaths = new Set([
     normalizeBlogRedirectPath(docsPath),
     normalizeBlogRedirectPath(`/blog/${docsPath}`),
   ])
 
-  const redirectedPost = allPosts.find((post) =>
-    (post.redirectFrom ?? []).some((redirectFrom) =>
-      normalizedPaths.has(normalizeBlogRedirectPath(redirectFrom)),
-    ),
-  )
+  const redirectedPostSlug = Array.from(normalizedPaths).flatMap((path) => {
+    const redirectOwner = redirectOwners[path]
+
+    return redirectOwner ? [redirectOwner] : []
+  })[0]
 
-  if (redirectedPost) {
+  if (redirectedPostSlug) {
     throw redirect({
-      href: `/blog/${redirectedPost.slug}`,
+      href: `/blog/${redirectedPostSlug}`,
     })
   }
 

src/utils/docs.ts

@@ -9,6 +9,7 @@ import { createServerFn } from '@tanstack/react-start'
 import * as v from 'valibot'
 import { setResponseHeader } from '@tanstack/react-start/server'
 import { fetchCached } from './cache.server'
+import { buildRedirectManifest, type RedirectManifestEntry } from './redirects'
 import { removeLeadingSlash } from './utils'
 
 export const loadDocs = async ({
@@ -176,13 +177,13 @@ async function getDocsRedirectManifest(opts: {
           const canonicalPath = getCanonicalDocsPath(node.path, docsRoot)
 
           if (canonicalPath === null) {
-            return [] as Array<readonly [string, string]>
+            return [] as Array<RedirectManifestEntry>
           }
 
           const file = await fetchRepoFile(repo, branch, node.path)
 
           if (!file) {
-            return [] as Array<readonly [string, string]>
+            return [] as Array<RedirectManifestEntry>
           }
 
           const frontMatter = extractFrontMatter(file)
@@ -194,12 +195,20 @@ async function getDocsRedirectManifest(opts: {
                 return []
               }
 
-              return [[redirectFrom, canonicalPath] as const]
+              return [
+                {
+                  from: redirectFrom,
+                  to: canonicalPath,
+                  source: node.path,
+                },
+              ]
             })
         }),
       )
 
-      return Object.fromEntries(entries.flat())
+      return buildRedirectManifest(entries.flat(), {
+        label: `docs redirects for ${repo}@${branch}:${docsRoot}`,
+      })
     },
   })
 }

src/utils/redirects.ts

@@ -0,0 +1,39 @@
+export type RedirectManifestEntry = {
+  from: string
+  to: string
+  source: string
+}
+
+export function buildRedirectManifest(
+  entries: Array<RedirectManifestEntry>,
+  opts: {
+    label: string
+    formatTarget?: (target: string) => string
+  },
+) {
+  const manifest: Record<string, string> = {}
+  const owners = new Map<string, { to: string; source: string }>()
+  const formatTarget = opts.formatTarget ?? ((target: string) => `/${target}`)
+
+  for (const entry of entries) {
+    const existingOwner = owners.get(entry.from)
+
+    if (
+      existingOwner &&
+      (existingOwner.to !== entry.to || existingOwner.source !== entry.source)
+    ) {
+      throw new Error(
+        [
+          `Duplicate redirect_from entry in ${opts.label}: /${entry.from}`,
+          `- ${existingOwner.source} -> ${formatTarget(existingOwner.to)}`,
+          `- ${entry.source} -> ${formatTarget(entry.to)}`,
+        ].join('\n'),
+      )
+    }
+
+    owners.set(entry.from, { to: entry.to, source: entry.source })
+    manifest[entry.from] = entry.to
+  }
+
+  return manifest
+}