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watch: strip watch flags from NODE_OPTIONS in child process #62143

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watch: strip watch flags from NODE_OPTIONS in child process #62143

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bb649d4
watch: strip watch flags from NODE_OPTIONS in child process
marcopiraccini Mar 7, 2026
125997b
watch: strip watch flags from NODE_OPTIONS in child process
marcopiraccini Mar 8, 2026
6bcc880
fixup
marcopiraccini Mar 8, 2026
91e21a9
fixup
marcopiraccini Mar 8, 2026
15f91f9
fixup after review
marcopiraccini Apr 9, 2026
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28 changes: 28 additions & 0 deletions lib/internal/main/watch_mode.js
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,7 @@ const {
ArrayPrototypePush,
ArrayPrototypePushApply,
ArrayPrototypeSlice,
RegExpPrototypeSymbolSplit,
StringPrototypeStartsWith,
} = primordials;

Expand Down Expand Up @@ -84,6 +85,32 @@ for (let i = 0; i < process.execArgv.length; i++) {

ArrayPrototypePushApply(argsWithoutWatchOptions, kCommand);

const kNodeOptions = process.env.NODE_OPTIONS;
let cleanNodeOptions = kNodeOptions;
if (kNodeOptions != null) {
const nodeOptionsArgs = [];
const parts = RegExpPrototypeSymbolSplit(/\s+/, kNodeOptions);
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@Renegade334 Renegade334 Mar 8, 2026 •
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Ultimately, this sort of approach isn't robust enough.

$ mkdir 'test for --watch parsing'
$ echo 'console.log("hi!")' > 'test for --watch parsing/test.cjs'
$ NODE_OPTIONS='--require "./test for --watch parsing/test.cjs"' node -p 'process.env.NODE_OPTIONS.split(" ")'
hi!
[ '--require', '"./test', 'for', '--watch', 'parsing/test.cjs"' ]
                                  ^^^^^^^

I suspect this is going to need to interact with the options parser in some way.

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@marcopiraccini marcopiraccini Mar 8, 2026

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Good catch.
Thinking about it, maybe adding a C++ binding that exposes ParseNodeOptionsEnvVar to JS would be more robust (being the same parser to interpret NODE_OPTIONS, in my undersanding) and then finltering out watch flags. Will amend this PR.

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@marcopiraccini marcopiraccini Mar 8, 2026

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@Renegade334 PTAL

for (let i = 0; i < parts.length; i++) {
const part = parts[i];
if (part === '') continue;
if (part === '--watch' ||
part === '--watch-preserve-output' ||
StringPrototypeStartsWith(part, '--watch=') ||
StringPrototypeStartsWith(part, '--watch-preserve-output=') ||
StringPrototypeStartsWith(part, '--watch-path=') ||
StringPrototypeStartsWith(part, '--watch-kill-signal=')) {
continue;
}
if (part === '--watch-path' || part === '--watch-kill-signal') {
// These flags take a separate value argument
i++;
continue;
}
ArrayPrototypePush(nodeOptionsArgs, part);
}
cleanNodeOptions = ArrayPrototypeJoin(nodeOptionsArgs, ' ');
}

const watcher = new FilesWatcher({ debounce: 200, mode: kShouldFilterModules ? 'filter' : 'all' });
ArrayPrototypeForEach(kWatchedPaths, (p) => watcher.watchPath(p));

Expand All @@ -99,6 +126,7 @@ function start() {
env: {
...process.env,
WATCH_REPORT_DEPENDENCIES: '1',
NODE_OPTIONS: cleanNodeOptions,
},
});
watcher.watchChildProcessModules(child);
Expand Down
33 changes: 33 additions & 0 deletions test/sequential/test-watch-mode.mjs
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Expand Up @@ -922,4 +922,37 @@ process.on('message', (message) => {
await done();
}
});

it('should strip all watch flags from NODE_OPTIONS in child process', async () => {
const file = createTmpFile('console.log(process.env.NODE_OPTIONS);');
const nodeOptions = [
'--watch', // bare boolean
'--watch=true', // boolean with =value
'--watch-path=./src', // string with =value
'--watch-path', './test', // String with space-separated value
'--watch-preserve-output', // bare boolean
'--watch-preserve-output=true', // boolean with =value
'--watch-kill-signal=SIGKILL', // string with =value
'--watch-kill-signal', 'SIGINT', // String with space-separated value
'--max-old-space-size=4096',
'--no-warnings',
].join(' ');
const { done, restart } = runInBackground({
args: ['--watch', file],
options: {
env: { ...process.env, NODE_OPTIONS: nodeOptions },
},
});

try {
const { stdout, stderr } = await restart();

assert.strictEqual(stderr, '');
const nodeOptionsLine = stdout.find((line) => line.includes('--max-old-space-size'));
assert.ok(nodeOptionsLine);
assert.strictEqual(nodeOptionsLine, '--max-old-space-size=4096 --no-warnings');
} finally {
await done();
}
});
});
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