chore: add comments

Author: ascorbic

packages/runtime/src/helpers/edge.ts

@@ -461,17 +461,19 @@ export const writeEdgeFunctions = async ({
         ...matchers.map((matcher) => middlewareMatcherToEdgeFunctionDefinition(matcher, functionName)),
       )
     }
+    // Functions (i.e. not middleware, but edge SSR and API routes)
     if (typeof middlewareManifest.functions === 'object') {
       // When using the app dir, we also need to check if the EF matches a page
       const appPathRoutesManifest = await loadAppPathRoutesManifest(netlifyConfig)
 
+      // A map of all route pages to their page regex. This is used for pages dir and appDir.
       const pageRegexMap = new Map(
         [...(routesManifest.dynamicRoutes || []), ...(routesManifest.staticRoutes || [])].map((route) => [
           route.page,
           route.regex,
         ]),
       )
-
+      // Create a map of pages-dir routes to their data route regex (appDir uses the same route as the HTML)
       const dataRoutesMap = new Map(
         [...(routesManifest.dataRoutes || [])].map((route) => [route.page, route.dataRouteRegex]),
       )
@@ -497,6 +499,7 @@ export const writeEdgeFunctions = async ({
           // cache: "manual" is currently experimental, so we restrict it to sites that use experimental appDir
           cache: usesAppDir ? 'manual' : undefined,
         })
+        // pages-dir page routes also have a data route. If there's a match, add an entry mapping that to the function too
         const dataRoute = dataRoutesMap.get(edgeFunctionDefinition.page)
         if (dataRoute) {
           manifest.functions.push({