[alpha.5] #4 — Route Lazy Loading

[SisyphusZheng]

Parent

#114 — v0.41.0-alpha.5: SPA Mode + Deno Desktop Proof

What to build

At build time, the Vite plugin (@openelement/adapter-vite) scans the routes/ directory and generates a client router manifest that maps route paths to lazy-loaded component imports. This enables route-level code splitting in SPA mode — only the current route's code is loaded on first page, and navigation triggers lazy-loading of the target route.

Build-time manifest generation:

• Plugin scans routes/**/*.tsx during vite build
• Generates a manifest like { '/': () => import('./routes/index.tsx'), '/products': () => import('./routes/products.tsx') }
• Injects the manifest into the client bundle

Runtime behavior:

• Router uses the manifest to resolve route → component mapping
• First navigation to a route triggers import() (code split point)
• Subsequent navigations to the same route reuse the cached module
• Loading state between navigation (lazy-loading a route for the first time shows a loading indicator or renders nothing until resolved)

Manual escape hatch:

• defineRoute({ path: '/admin', lazy: () => import('./routes/admin.tsx') }) supported but unnecessary for file-system routes

Acceptance criteria

• deno task build generates a route manifest from routes/*.tsx files
• Router reads the manifest and lazy-loads routes on first access
• First page load only includes the current route's code in the bundle
• Navigation to a new route triggers import() for the target route
• Repeated navigation to the same route reuses the cached module (no re-import)
• defineRoute({ lazy: () => import(...) }) manual override works
• Tests cover: manifest generation, lazy load on navigate, cache reuse, manual override

Blocked by

None — can start immediately (parallel with #115)

[SisyphusZheng]

Implemented in PR #121 (dev → main). 93/93 tests pass.