fix(build): resolve additional configs by source path

Discovered config files are keyed by their source directory, but the
lookup walked the rewrite-applied relativePath, so directories covered
by rewrites silently lost their additional config. Resolve against
pageData.filePath on both server and client, which also makes dynamic
route pages inherit configs from their route template's directory.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/client/app/data.ts

@@ -29,7 +29,11 @@ export const siteDataRef: Ref<SiteData> = shallowRef(
 // per-app data
 export function initData(route: Route): VitePressData {
   const site = computed(() =>
-    resolveSiteDataByRoute(siteDataRef.value, route.data.relativePath)
+    resolveSiteDataByRoute(
+      siteDataRef.value,
+      route.data.relativePath,
+      route.data.filePath
+    )
   )
 
   const appearance = site.value.appearance // fine with reactivity being lost here, config change triggers a restart

src/node/build/render.ts

@@ -34,7 +34,6 @@ export async function renderPage(
   usedIcons: Set<string>
 ) {
   const routePath = `/${page.replace(/\.md$/, '')}`
-  const siteData = resolveSiteDataByRoute(config.site, page)
 
   // render page
   const context = await render(routePath)
@@ -70,6 +69,8 @@ export async function renderPage(
     }
   }
 
+  const siteData = resolveSiteDataByRoute(config.site, page, pageData.filePath)
+
   const title: string = createTitle(siteData, pageData)
   const description: string = pageData.description || siteData.description
   const stylesheetLink = cssChunk

src/shared/shared.ts

@@ -109,14 +109,20 @@ export function getLocaleForPath(
  */
 export function resolveSiteDataByRoute(
   siteData: SiteData,
-  relativePath: string
+  relativePath: string,
+  filePath?: string
 ): SiteData {
   const localeIndex = getLocaleForPath(siteData, relativePath)
   const { label, link, markdown, ...localeConfig } =
     siteData.locales[localeIndex] ?? {}
   Object.assign(localeConfig, { localeIndex })
 
-  const additionalConfigs = resolveAdditionalConfig(siteData, relativePath)
+  // additional configs are colocated with sources, so resolve them by the
+  // source path (filePath) rather than the rewritten one
+  const additionalConfigs = resolveAdditionalConfig(
+    siteData,
+    filePath || relativePath
+  )
 
   if (inBrowser && (import.meta as any).env?.DEV) {
     ;(localeConfig as any)[VP_SOURCE_KEY] = `locale config (${localeIndex})`

types/shared.d.ts

@@ -246,9 +246,11 @@ export interface SiteData<ThemeConfig = any> {
     prefetchLinks: boolean
   }
   /**
-   * Config overrides applied to pages by directory: either a dict mapping a
-   * directory (e.g. `/guide/`) to overrides, where deeper directories take
-   * precedence, or a function returning the overrides to apply for a page.
+   * Config overrides applied to pages by source directory: either a dict
+   * mapping a directory (e.g. `/guide/`) to overrides, where deeper
+   * directories take precedence, or a function returning the overrides to
+   * apply for a page. Directories are resolved against the source paths of
+   * pages, before rewrites.
    */
   additionalConfig?:
     AdditionalConfigDict<ThemeConfig> | AdditionalConfigLoader<ThemeConfig>
@@ -523,7 +525,8 @@ export type AdditionalConfig<ThemeConfig = any> =
   LocaleSpecificConfig<ThemeConfig>
 
 /**
- * Additional configs keyed by the directory they apply to (e.g. `/guide/`).
+ * Additional configs keyed by the source directory they apply to
+ * (e.g. `/guide/`).
  */
 export type AdditionalConfigDict<ThemeConfig = any> = Record<
   string,
@@ -531,11 +534,11 @@ export type AdditionalConfigDict<ThemeConfig = any> = Record<
 >
 
 /**
- * Resolves the additional configs of a page from its relative path, ordered
+ * Resolves the additional configs of a page from its source path, ordered
  * from highest to lowest priority.
  */
 export type AdditionalConfigLoader<ThemeConfig = any> = (
-  relativePath: string
+  filePath: string
 ) => AdditionalConfig<ThemeConfig>[] | void
 
 // Manually declaring all properties as rollup-plugin-dts