packages/nuxt/src/core/app.ts (3)

217-220: Duplicate normalisation runs; consider consolidating to a single pass

You normalise/dedupe middleware and plugins once before assignment, and again after the hook. That’s extra work every resolve and can be surprising for future maintainers.

Options:

• Keep the post-hook pass (based on app.* as suggested) and drop this pre-hook pass, or
• Keep this pre-hook pass to provide fully-resolved values to 'app:resolve' and drop the post-hook pass.

Given the potential for 'app:resolve' to mutate arrays, keeping only the post-hook pass is cleaner, but either way avoid both.

For example, to drop the pre-hook pass:

-  middleware = uniqueBy(await resolvePaths(nuxt, [...middleware].reverse(), 'path'), 'name').reverse()
-  plugins = uniqueBy(await resolvePaths(nuxt, plugins, 'src'), 'src')

---

195-207: Plugin aggregation and normalisation approach is sound

Gathering from layered configs and templated files before normalisation is clear. Forced casting in normalizePlugin(plugin as NuxtPlugin) is a minor smell but acceptable here if upstream types are broad.

If you want to avoid the cast, consider narrowing config.plugins at the source or adding a small type guard for plugin-like objects.

---

210-215: Re-introducing unspecified plugins preserves user order

Iterating reversed and unshifting maintains original user-specified order at the front. One nit: the inner some(p => p.src === plugin.src) shadows the outer p. Rename for readability.

-    if (!plugins.some(p => p.src === plugin.src)) {
+    if (!plugins.some(existing => existing.src === plugin.src)) {
       plugins.unshift(plugin)
     }

packages/nuxt/test/app.test.ts (1)

269-301: Good guard against exposing partial app structures

The Proxy-based test effectively ensures that layouts/middleware/plugins are only set with non-empty values, validating the “assign once when resolved” contract.

Two optional improvements:

• Track write counts per property to ensure exactly one assignment occurs for each of 'layouts', 'middleware', 'plugins' (stricter regression guard).
• Add a companion test that mutates app.* in an 'app:resolve' hook (e.g. pushing a plugin) and asserts the mutation persists post-resolve. This would catch the overwrite issue flagged in core.

Example augmentation for write counts:

-    const app = new Proxy(_app, {
+    const writes: Record<string, number> = { layouts: 0, middleware: 0, plugins: 0 }
+    const app = new Proxy(_app, {
       get (target, p, receiver) {
         return Reflect.get(target, p, receiver)
       },
       set (target, p, newValue, receiver) {
         if (p === 'middleware' || p === 'plugins') {
           expect(newValue).not.toEqual([])
+          writes[p as string]!++
         }
         if (p === 'layouts') {
           expect(newValue).not.toEqual({})
+          writes[p as string]!++
         }
         return Reflect.set(target, p, newValue, receiver)
       },
     })
 
     await resolveApp(nuxt, app)
+    expect(writes).toEqual({ layouts: 1, middleware: 1, plugins: 1 })

If you’d like, I can draft the hook-mutation test as well.

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Learnt from: GalacticHypernova
PR: nuxt/nuxt#26468
File: packages/nuxt/src/components/plugins/loader.ts:24-24
Timestamp: 2024-11-05T15:22:54.759Z
Learning: In `packages/nuxt/src/components/plugins/loader.ts`, the references to `resolve` and `distDir` are legacy code from before Nuxt used the new unplugin VFS and will be removed.

Learnt from: GalacticHypernova
PR: nuxt/nuxt#26468
File: packages/nuxt/src/components/plugins/loader.ts:24-24
Timestamp: 2024-11-05T15:22:54.759Z
Learning: In `packages/nuxt/src/components/plugins/loader.ts`, the references to `resolve` and `distDir` are legacy code from before Nuxt used the new unplugin VFS and will be removed.