perf(dev): stop saves that change nothing from restarting the dev server

[danielroe]

🔗 Linked issue

📚 Description

this avoids too-eager restarts of nuxt cli

[pkg-pr-new]

• nuxt-cli-playground

  npm i https://pkg.pr.new/create-nuxt@1435
  

  npm i https://pkg.pr.new/nuxi@1435
  

  npm i https://pkg.pr.new/@nuxt/cli@1435
  

commit: 9515b53

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 142a4c4c-9cb9-478d-af66-a83d5f37ca69

📥 Commits

Reviewing files that changed from the base of the PR and between 3a4553d and 9515b53.

📒 Files selected for processing (1)

• packages/nuxt-cli/src/dev/utils.ts

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📝 Walkthrough

Walkthrough

FileChangeTracker now uses SHA-1 content hashes for files up to 256 KiB and retains modification-time tracking for directories, larger files, and hash failures. Identical rewrites no longer emit changes. The new perFile helper debounces events independently by path and cancels pending callbacks during watcher cleanup. Root and .config watchers use this helper. Tests cover hashing, atomic saves, oversized files, event coalescing, and cancellation.

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

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly states that unchanged saves will no longer restart the development server.
Description check	✅ Passed	The description directly explains that the changes prevent overly eager Nuxt CLI development server restarts.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch perf/restarts

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@packages/nuxt-cli/src/dev/utils.ts`:
- Around line 110-115: Update hashFileContents to read through a file descriptor
with a buffer limited to MAX_HASHED_FILE_SIZE + 1 bytes instead of reading the
entire file via readFileSync. If the extra byte is present, return the existing
mtime-based fallback; otherwise hash only the bytes read, while preserving the
current size guard and error handling.

🪄 Autofix

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: b3b51cd3-ed7c-45e3-96f5-e72afa4f2997

📥 Commits

Reviewing files that changed from the base of the PR and between 585278a and 3a4553d.

📒 Files selected for processing (3)

• packages/nuxt-cli/src/dev/utils.ts
• packages/nuxt-cli/test/unit/file-watcher.spec.ts
• packages/nuxt-cli/test/unit/per-file.spec.ts

[codspeed-hq]

Merging this PR will not alter performance

✅ 2 untouched benchmarks

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_{Comparing perf/restarts (9515b53) with main (585278a)}