fix(runtime): add multi-app support for global var __NUXT__

[nicolaspayot]

resolves #1521

This PR adds multi-app support for global variable win.__NUXT__.

These changes are related to the multi-app issue in nuxt: nuxt/nuxt#21635 and required for the following draft PR: nuxt/nuxt#27263.

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/@nuxt/test-utils@858

npm i https://pkg.pr.new/vitest-environment-nuxt@858

commit: 4774ab9

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Run ID: aa92a3e1-9c95-4709-a060-0146f362faaa

📥 Commits

Reviewing files that changed from the base of the PR and between d84d63a and 4774ab9.

⛔ Files ignored due to path filters (1)

• pnpm-lock.yaml is excluded by !**/pnpm-lock.yaml

📒 Files selected for processing (3)

• examples/app-vitest-workspace/app3/test/browser/render.spec.ts
• examples/multi-app/package.json
• src/config.ts

🚧 Files skipped from review as they are similar to previous changes (1)

• examples/multi-app/package.json

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📝 Walkthrough

Walkthrough

The change adds multi-app Nuxt runtime state handling through nuxtAppId and nuxtFuture environment options. It adds a multi-app example with a counter page, composable, Vitest configuration, and Nuxt and browser tests. It also adds application shells and corrects app.vue import aliases in the workspace example.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Merge Risk: ⚪ Minimal · up to 4774a

This change adds multi-app support for the test environment’s Nuxt global state without introducing an actionable merge-blocking risk. It is merge-ready after normal checks and review.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 2 functions across 3 files. (1 skipped: 1 …	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the main change: adding multi-app support for the global __NUXT__ runtime variable.
Description check	✅ Passed	The description directly explains the multi-app win.__NUXT__ change and links it to the related Nuxt issue and follow-up work.
Linked Issues check	✅ Passed	The changes address issue #1521 by passing multi-app configuration into the test environment, storing the runtime object under the configured app ID, and adding multi-app Nuxt and browser test coverag…
Out of Scope Changes check	✅ Passed	The source changes, configuration updates, examples, and tests are related to multi-app runtime support and Vitest integration. No unrelated code changes are evident.

Full details: Linked Issues check

Explanation

The changes address issue #1521 by passing multi-app configuration into the test environment, storing the runtime object under the configured app ID, and adding multi-app Nuxt and browser test coverage.

Full details: Docstring Coverage

Explanation

Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 2 functions across 3 files. (1 skipped: 1 unsupported.)

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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