fix(react-router): a lazy route follows a barrel that re-exports an import (#2558)

A lazily loaded folder whose index passes on a page it imports linked
nothing: DigiShop.Frontend's `src/layout/index.ts` does `import { UserLayout }
from './UserLayout'; export { UserLayout }`, and its routes load
`await import('@/layout')`. exportedComponent, the barrel walk behind lazy
routes, React.lazy values and lazy layouts (#2436, #2452, #2480), read the
export clause as naming a declaration in the barrel, which has none: the
name is an import binding. `import Login from './Login'; export default
Login` and `export { Page as Component }` of an imported Page failed the
same way, so all 27 lazy route refs in DigiShop's App.tsx stayed failed.

A binding the module exports but does not declare is now followed through
the module's import of it, a default import as `default` and a named one by
the name it imports, with each file read added to `reads` so lazyModules
still redraws the route. A namespace import or a package's binding links
nothing. `export default withAuth(Page)` hands over a call, whose first
identifier ownExport reads; that was harmless while only same-file
declarations counted, so a default is followed only when the statement is
the binding itself (exportsBinding), or the route would link the HOC.

#2451 (open) adds the same step to the general import walk; #2420 (open)
carried it in a lazyRouteComponent rewrite that exportedComponent superseded.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/design/framework-coverage.md

@@ -38,7 +38,7 @@ guessed.
 |---|---|---|---|---|
 | Expo Router | `frameworks/expo-router.ts` | `expo-router-synthesizer.ts` | `expo-router.test.ts` | — |
 | Next.js | `frameworks/nextjs.ts` | `next-router-synthesizer.ts` | `nextjs.test.ts` | next-saas-starter |
-| React Router | `frameworks/react-router.ts` | `react-router-synthesizer.ts` | `react-router.test.ts` | proshop (44 edges), proshop-v2 (28), react-redux-realworld (22), react-boilerplate (`styled(Link)`), takenote (v5 `<Redirect>`), bulletproof-react (nested `children`, `lazy` routes, `paths.x.path` constants through an app's own tsconfig alias: 0 → 9 named, linked routes), and its `paths.x.getHref(id)` links and `navigate(paths.x.getHref())` calls (0 → 11 navigates). Route tables another file hands the router (`tableRoutes` in `frameworks/react.ts`, trap 13): the ASP.NET Core React template's `AppRoutes.map(… <Route {...rest}>)` on jasontaylordev/CleanArchitecture's `ClientApp-React` (0 → 6 routes, 11 navigates), replaysMike/Binner (0 → 46, 87), GavinLonDigital/RankingApp, GarrettHays/PaydirtPickem, charlessolar/eShopOnContainersDDD; `useRoutes(routes)` from another file and `[...sessionRoutes]` on uilibrary/matx-react (0 → 7, 16); codedthemes' `createBrowserRouter([MainRoutes, LoginRoutes])` on berry and mantis (9 and 8 routes, no navigation they can resolve); a table `.map`ped inside `<Route path="/dashboard">` on RADeveloping/chickadeeinvest; `useRoutes([...])` in place on minimal-ui-kit/material-kit-react (0 → 7, bound through `lazy(() => import(…))` to each page). JSX index routes and layouts (trap 14): proshop-v2's `createRoutesFromElements` (`/` is HomeScreen inside App, not App; 30 layout edges, the `path=''` guards included; Screens 30 → 74 transitions, the guards' redirects drawn from the screens they guard), chickadeeinvest's table inside `<Route element={<DashboardLayout/>}>` (its 4 routes get the layout), React Router 6.29's own examples and tests, refine's 281 examples (one `/` per app, 191 layout edges, 21 new navigations), crwn-clothing, the vanlife course app, volun-mern (105 layout edges, six levels deep), spotify/vispana, react_persist_login, chushi (`path={"agents"}`: 2 → 6 routes), hathor-explorer (`path=""` at the root), cboard, react-router-auth-v6: 578 of 581 new layout edges name a component of an enclosing `<Route>` (vanlife's 3 inherit a default-import resolution bug that already misbinds its pages), 27 of 27 new navigations precise, no navigation lost, 16 control repos byte-identical. Lazy route modules that are barrels (`exportedComponent` in `frameworks/react.ts`): luci-go's milo/ui (`export * from './x'` index files and `export { X as Component }` clauses: 0 → 51 lazy routes linked; the other 40 load a file under `src/build/`, which the default ignore skips, export only a `loader` or a `handle`, or pick a named export in an async `lazy`), Medusa's admin dashboard (all 193 route-map modules resolve through its `export { X as Component } from` barrels, but its routes are not extracted: `getRouteMap()` returns the table), four more apps (9 routes), 16 control repos byte-identical. Lazy loaders that pick their page (`lazyRouteReference` in `frameworks/react.ts`, trap 18): milo/ui's three tabs (`const { TestTab } = await import('…/tabs')`), 20 apps from a GitHub survey of `createBrowserRouter` + `lazy` (636 picked-page edges, each checked against the target file's own export: 467 by name, 169 as its `export default`; 42 routes written with `async lazy()` now indexed, among them React Router's own `lazy-loading-router-provider` example), an AST oracle on the TypeScript compiler agreeing with the text reader on all 2,538 loaders of 876 surveyed router files, a late-file sync equal to a fresh index on 8 of those apps, and 26 control repos byte-identical, among them ghostfolio, whose 30 Angular lazy routes stay Angular's with React detected in the same project |
+| React Router | `frameworks/react-router.ts` | `react-router-synthesizer.ts` | `react-router.test.ts` | proshop (44 edges), proshop-v2 (28), react-redux-realworld (22), react-boilerplate (`styled(Link)`), takenote (v5 `<Redirect>`), bulletproof-react (nested `children`, `lazy` routes, `paths.x.path` constants through an app's own tsconfig alias: 0 → 9 named, linked routes), and its `paths.x.getHref(id)` links and `navigate(paths.x.getHref())` calls (0 → 11 navigates). Route tables another file hands the router (`tableRoutes` in `frameworks/react.ts`, trap 13): the ASP.NET Core React template's `AppRoutes.map(… <Route {...rest}>)` on jasontaylordev/CleanArchitecture's `ClientApp-React` (0 → 6 routes, 11 navigates), replaysMike/Binner (0 → 46, 87), GavinLonDigital/RankingApp, GarrettHays/PaydirtPickem, charlessolar/eShopOnContainersDDD; `useRoutes(routes)` from another file and `[...sessionRoutes]` on uilibrary/matx-react (0 → 7, 16); codedthemes' `createBrowserRouter([MainRoutes, LoginRoutes])` on berry and mantis (9 and 8 routes, no navigation they can resolve); a table `.map`ped inside `<Route path="/dashboard">` on RADeveloping/chickadeeinvest; `useRoutes([...])` in place on minimal-ui-kit/material-kit-react (0 → 7, bound through `lazy(() => import(…))` to each page). JSX index routes and layouts (trap 14): proshop-v2's `createRoutesFromElements` (`/` is HomeScreen inside App, not App; 30 layout edges, the `path=''` guards included; Screens 30 → 74 transitions, the guards' redirects drawn from the screens they guard), chickadeeinvest's table inside `<Route element={<DashboardLayout/>}>` (its 4 routes get the layout), React Router 6.29's own examples and tests, refine's 281 examples (one `/` per app, 191 layout edges, 21 new navigations), crwn-clothing, the vanlife course app, volun-mern (105 layout edges, six levels deep), spotify/vispana, react_persist_login, chushi (`path={"agents"}`: 2 → 6 routes), hathor-explorer (`path=""` at the root), cboard, react-router-auth-v6: 578 of 581 new layout edges name a component of an enclosing `<Route>` (vanlife's 3 inherit a default-import resolution bug that already misbinds its pages), 27 of 27 new navigations precise, no navigation lost, 16 control repos byte-identical. Lazy route modules that are barrels (`exportedComponent` in `frameworks/react.ts`): luci-go's milo/ui (`export * from './x'` index files and `export { X as Component }` clauses: 0 → 51 lazy routes linked; the other 40 load a file under `src/build/`, which the default ignore skips, export only a `loader` or a `handle`, or pick a named export in an async `lazy`), Medusa's admin dashboard (all 193 route-map modules resolve through its `export { X as Component } from` barrels, but its routes are not extracted: `getRouteMap()` returns the table), four more apps (9 routes), 16 control repos byte-identical. Lazy loaders that pick their page (`lazyRouteReference` in `frameworks/react.ts`, trap 18): milo/ui's three tabs (`const { TestTab } = await import('…/tabs')`), 20 apps from a GitHub survey of `createBrowserRouter` + `lazy` (636 picked-page edges, each checked against the target file's own export: 467 by name, 169 as its `export default`; 42 routes written with `async lazy()` now indexed, among them React Router's own `lazy-loading-router-provider` example), an AST oracle on the TypeScript compiler agreeing with the text reader on all 2,538 loaders of 876 surveyed router files, a late-file sync equal to a fresh index on 8 of those apps, and 26 control repos byte-identical, among them ghostfolio, whose 30 Angular lazy routes stay Angular's with React detected in the same project. Barrels that pass on a page they import (`import { UserLayout } from './UserLayout'; export { UserLayout }`, `import Login from './Login'; export default Login`; `exportedComponent` follows the import): Arshia76/DigiShop.Frontend (0 → 27 route and layout edges), 49 other repos byte-identical; `export default withAuth(Page)` is followed nowhere. Known limit, shared with #2436's `export *` barrels: a page in a folder below the barrel's (`pages/Home/index.tsx` behind `@/pages`) is linked by a fresh index but not by a sync that adds it later, because the route's failed reference waits under the barrel's module key (`module:pages`) |
 | TanStack Router | `frameworks/tanstack-router.ts` | `tanstack-router-synthesizer.ts` | `tanstack-router.test.ts` | TanStack examples, fastapi-template frontend |
 | Vue Router / Nuxt | `frameworks/vue-router.ts` (Nuxt file routes: `nuxtResolver` in `frameworks/vue.ts`) | `vue-router-synthesizer.ts` | `vue-router.test.ts` | vue-realworld (23 edges); vue-element-admin (62 routes), vue-admin-template (14), vben (192), halo console (34) — named tables, module files, `children` + layouts; Nuxt: mealie, elk, nuxt/movies |
 | SvelteKit | `frameworks/sveltekit-router.ts` | `sveltekit-synthesizer.ts` | `sveltekit-router.test.ts`, `sveltekit-route-names.test.ts` | sveltekit-realworld (31 edges); shadcn-svelte and skeleton (`(group)` layouts: 13 and 23 edges), svelte.dev (74), kit's test apps (47) |