fix: Deduplicate redirect errors to one per redirect

Report the most actionable error (section mismatch over file-not-found)
and skip redundant checks. Also simplify by removing duplicated logic.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: louis-pre

codegen/validate-redirects.ts

@@ -6,6 +6,7 @@ import YAML from 'yaml'
 import { siteSections } from './lib/config.js'
 
 interface GitbookConfig {
+  root?: string
   redirects?: Record<string, string>
 }
 
@@ -16,102 +17,81 @@ interface BrokenRedirect {
   reason: string
 }
 
+function findForeignSection(
+  path: string,
+  ownRoot: string,
+): string | undefined {
+  for (const other of siteSections) {
+    if (other.root === ownRoot) continue
+    const prefix = other.urlPrefix.replace(/^\//, '') + '/'
+    if (prefix !== '/' && path.startsWith(prefix)) return other.name
+  }
+  return undefined
+}
+
 const broken: BrokenRedirect[] = []
 
+interface ConfigToValidate {
+  configPath: string
+  root: string
+  redirects: Record<string, string>
+}
+
+const configs: ConfigToValidate[] = []
+
 for (const section of siteSections) {
   const configPath = join(section.root, '.gitbook.yaml')
   if (!existsSync(configPath)) continue
-
   const config = YAML.parse(readFileSync(configPath, 'utf-8')) as GitbookConfig
-  const redirects = config.redirects ?? {}
-  for (const [source, target] of Object.entries(redirects)) {
-    // Source must not start with another section's URL prefix
-    for (const other of siteSections) {
-      if (other.root === section.root) continue
-      const otherPrefix = other.urlPrefix.replace(/^\//, '') + '/'
-      if (otherPrefix !== '/' && source.startsWith(otherPrefix)) {
-        broken.push({
-          configPath,
-          source,
-          target,
-          reason: `Source belongs to the "${other.name}" section, not "${section.name}". Move this redirect to ${join(other.root, '.gitbook.yaml')}`,
-        })
-      }
-    }
-
-    // Target must not start with another section's URL prefix
-    for (const other of siteSections) {
-      if (other.root === section.root) continue
-      const otherPrefix = other.urlPrefix.replace(/^\//, '') + '/'
-      if (otherPrefix !== '/' && target.startsWith(otherPrefix)) {
-        broken.push({
-          configPath,
-          source,
-          target,
-          reason: `Target points to the "${other.name}" section. Move this redirect to ${join(other.root, '.gitbook.yaml')}`,
-        })
-      }
-    }
-
-    // Target must resolve to an existing file within this section
-    const fullPath = join(section.root, target)
-    if (!existsSync(fullPath) || !statSync(fullPath).isFile()) {
-      broken.push({
-        configPath,
-        source,
-        target,
-        reason: `File not found: ${fullPath}`,
-      })
-    }
-  }
+  configs.push({
+    configPath,
+    root: section.root,
+    redirects: config.redirects ?? {},
+  })
 }
 
-// Also check the root .gitbook.yaml if it's not already a section config
 const rootConfigPath = '.gitbook.yaml'
-const rootIsSection = siteSections.some(
-  (s) => join(s.root, '.gitbook.yaml') === rootConfigPath,
-)
-
+const rootIsSection = configs.some((c) => c.configPath === rootConfigPath)
 if (!rootIsSection && existsSync(rootConfigPath)) {
   const config = YAML.parse(
     readFileSync(rootConfigPath, 'utf-8'),
-  ) as GitbookConfig & { root?: string }
-  const redirects = config.redirects ?? {}
+  ) as GitbookConfig
   const root = (config.root ?? './').replace(/^\.\//, '').replace(/\/$/, '')
+  configs.push({
+    configPath: rootConfigPath,
+    root,
+    redirects: config.redirects ?? {},
+  })
+}
 
-  const section = siteSections.find((s) => s.root === root)
-
+for (const { configPath, root, redirects } of configs) {
   for (const [source, target] of Object.entries(redirects)) {
-    for (const other of siteSections) {
-      if (section != null && other.root === section.root) continue
-      const otherPrefix = other.urlPrefix.replace(/^\//, '') + '/'
-      if (otherPrefix !== '/' && source.startsWith(otherPrefix)) {
-        broken.push({
-          configPath: rootConfigPath,
-          source,
-          target,
-          reason: `Source belongs to the "${other.name}" section. Move this redirect to ${join(other.root, '.gitbook.yaml')}`,
-        })
-      }
+    const foreignSource = findForeignSection(source, root)
+    if (foreignSource != null) {
+      broken.push({
+        configPath,
+        source,
+        target,
+        reason: `Source belongs to the "${foreignSource}" section. Move this redirect to that section's .gitbook.yaml`,
+      })
+      continue
     }
 
-    for (const other of siteSections) {
-      if (section != null && other.root === section.root) continue
-      const otherPrefix = other.urlPrefix.replace(/^\//, '') + '/'
-      if (otherPrefix !== '/' && target.startsWith(otherPrefix)) {
-        broken.push({
-          configPath: rootConfigPath,
-          source,
-          target,
-          reason: `Target points to the "${other.name}" section. Move this redirect to ${join(other.root, '.gitbook.yaml')}`,
-        })
-      }
+    const foreignTarget = findForeignSection(target, root)
+    if (foreignTarget != null) {
+      broken.push({
+        configPath,
+        source,
+        target,
+        reason: `Target points to the "${foreignTarget}" section. Move this redirect to that section's .gitbook.yaml`,
+      })
+      continue
     }
 
     const fullPath = join(root, target)
     if (!existsSync(fullPath) || !statSync(fullPath).isFile()) {
       broken.push({
-        configPath: rootConfigPath,
+        configPath,
         source,
         target,
         reason: `File not found: ${fullPath}`,