feat(dev): pause and resume HMR during file changes#1297
feat(dev): pause and resume HMR during file changes#1297martin-mastermind wants to merge 1 commit intonuxt:mainfrom
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Add ability to temporarily pause Vite and Nitro HMR when processing multiple file changes, particularly useful when AI agents auto-save edits. Files can be accumulated silently, then reloaded in a single batch when changes are complete. Keyboard shortcut: Press 'p' in the dev terminal to toggle pause. Alternative: Create/delete .hmr-pause file in project root. Changes: - Wrap viteServer.hot.send to buffer HMR messages when paused - Guard load() to queue pending reloads instead of executing immediately - Watch sentinel file (.hmr-pause) to trigger pause/resume state changes - Add stdin keyboard handler for 'p' key to toggle pause state Fixes nuxt#1223
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📝 WalkthroughWalkthroughThe change implements a keyboard-controlled pause/resume mechanism for Vite HMR in the Nuxt dev server. In TTY environments, pressing the 'p' key creates or removes a Estimated code review effort🎯 3 (Moderate) | ⏱️ ~25 minutes 🚥 Pre-merge checks | ✅ 5✅ Passed checks (5 passed)
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Actionable comments posted: 4
🤖 Prompt for all review comments with AI agents
Verify each finding against the current code and only fix it if needed.
Inline comments:
In `@packages/nuxi/src/commands/dev.ts`:
- Around line 90-105: Wrap the stdin setup (process.stdin.setRawMode,
process.stdin.resume, process.stdin.setEncoding, and the data listener that
toggles the '.hmr-pause' sentinel) into a scope where you also create a
cleanupStdin function that removes the 'data' listener and restores raw mode (if
setRawMode exists) and pauses stdin; then call cleanupStdin from every
shutdown/close path in this module (the handlers that currently return without
cleanup) so the terminal state is always restored. Ensure cleanupStdin
references the exact listener function you passed to process.stdin.on('data',
...) so it can be detached, and invoke it before any early return or process
exit.
- Around line 95-103: In the process.stdin.on('data') handler (the key === 'p'
branch) avoid the check-then-act race by removing the existsSync + rmSync
pattern and call rmSync(sentinelPath, { force: true }) to delete the sentinel
safely (or wrap the whole branch in a try-catch); keep the
writeFileSync(sentinelPath, '') for the create case, and ensure you update the
logic around sentinelPath/resolve so the deletion uses rmSync with the force
option to prevent ENOENT from crashing the dev server.
In `@packages/nuxi/src/dev/utils.ts`:
- Around line 245-249: closeWatchers currently closes `#sentinelWatcher` and
`#distWatcher` but calls `#configWatcher` as a function; ensure you call .close() on
watchers (use this.#configWatcher?.close()) and avoid permanently removing the
sentinel watcher: modify load() to re-register the `.hmr-pause` sentinel watcher
after a reload (or move sentinel watcher setup into a helper that's invoked both
on initial start and inside load()), and ensure closeWatchers only closes
watchers (this.#sentinelWatcher?.close(); this.#distWatcher?.close();
this.#configWatcher?.close()) so that the sentinel can be re-created by the
load() re-registration logic (affects closeWatchers and the load() watcher
setup).
- Around line 345-347: The fs.watch callback currently returns early when
filename is null/undefined due to the strict check in the watcher assigned to
this.#sentinelWatcher; update the callback used with watch so it only compares
filename when defined (e.g., if (filename && filename !== '.hmr-pause') return)
or remove the filename guard so the sentinelPath existence check always runs;
ensure the logic that calls existsSync(sentinelPath) then calls this.pause() or
this.resume() remains intact and referenced from the same watcher callback.
🪄 Autofix (Beta)
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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Configuration used: Organization UI
Review profile: CHILL
Plan: Pro
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📒 Files selected for processing (2)
packages/nuxi/src/commands/dev.tspackages/nuxi/src/dev/utils.ts
| if (key === 'p') { | ||
| const sentinelPath = resolve(cwd, '.hmr-pause') | ||
| if (existsSync(sentinelPath)) { | ||
| rmSync(sentinelPath) | ||
| } | ||
| else { | ||
| writeFileSync(sentinelPath, '') | ||
| } | ||
| } |
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process.stdin.setRawMode(true);
process.stdin.resume();
process.stdin.setEncoding('utf8');
// Set up error handler for stdin
process.stdin.on('error', (err) => {
console.log('stdin error handler caught:', err.message);
});
process.stdin.on('data', (key) => {
console.log('Received key:', key);
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if (key === 'p') {
throw new Error('ENOENT: no such file or directory');
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Use exception-safe file operations in the stdin event handler.
Lines 96-102 use a check-then-act pattern (existsSync + rmSync) that can throw ENOENT if the file is deleted between the check and deletion. Since this code runs inside a process.stdin.on('data') event handler with no error boundary, an uncaught exception will crash the dev server. Replace with rmSync(sentinelPath, { force: true }) to safely handle both the race condition and non-existent files, or wrap the operations in a try-catch block.
🤖 Prompt for AI Agents
Verify each finding against the current code and only fix it if needed.
In `@packages/nuxi/src/commands/dev.ts` around lines 95 - 103, In the
process.stdin.on('data') handler (the key === 'p' branch) avoid the
check-then-act race by removing the existsSync + rmSync pattern and call
rmSync(sentinelPath, { force: true }) to delete the sentinel safely (or wrap the
whole branch in a try-catch); keep the writeFileSync(sentinelPath, '') for the
create case, and ensure you update the logic around sentinelPath/resolve so the
deletion uses rmSync with the force option to prevent ENOENT from crashing the
dev server.
| closeWatchers(): void { | ||
| this.#sentinelWatcher?.close() | ||
| this.#distWatcher?.close() | ||
| this.#configWatcher?.() | ||
| } |
There was a problem hiding this comment.
Re-register the .hmr-pause watcher after reload.
Line 246 closes #sentinelWatcher, but load() only reattaches config watching (Line 272). After first reload, sentinel toggling no longer works.
Proposed fix
@@
}
- this.#watchConfig()
+ this.#watchConfig()
+ this.#watchSentinel()
}Also applies to: 258-273
🤖 Prompt for AI Agents
Verify each finding against the current code and only fix it if needed.
In `@packages/nuxi/src/dev/utils.ts` around lines 245 - 249, closeWatchers
currently closes `#sentinelWatcher` and `#distWatcher` but calls `#configWatcher` as a
function; ensure you call .close() on watchers (use
this.#configWatcher?.close()) and avoid permanently removing the sentinel
watcher: modify load() to re-register the `.hmr-pause` sentinel watcher after a
reload (or move sentinel watcher setup into a helper that's invoked both on
initial start and inside load()), and ensure closeWatchers only closes watchers
(this.#sentinelWatcher?.close(); this.#distWatcher?.close();
this.#configWatcher?.close()) so that the sentinel can be re-created by the
load() re-registration logic (affects closeWatchers and the load() watcher
setup).
1 participant
🔗 Linked issue
Fixes #1223
📚 Description
Add ability to temporarily pause Vite and Nitro HMR when processing multiple file changes, particularly useful when AI agents auto-save edits. Files can be accumulated silently, then reloaded in a single batch when changes are complete.
Keyboard shortcut: Press 'p' in the dev terminal to toggle pause.
Alternative: Create/delete .hmr-pause file in project root.
Changes: