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test: cover thrown errors from exec() kill #11038

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test: cover thrown errors from exec() kill #11038

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29 changes: 29 additions & 0 deletions test/parallel/test-child-process-exec-kill-throws.js
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Original file line number Diff line number Diff line change
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'use strict';
// Flags: --expose_internals
const common = require('../common');
const assert = require('assert');
const cp = require('child_process');
const internalCp = require('internal/child_process');

if (process.argv[2] === 'child') {
// Keep the process alive and printing to stdout.
setInterval(() => { console.log('foo'); }, 1);
} else {
// Monkey patch ChildProcess#kill() to kill the process and then throw.
const kill = internalCp.ChildProcess.prototype.kill;

internalCp.ChildProcess.prototype.kill = function() {
kill.apply(this, arguments);
throw new Error('mock error');
};

const cmd = `${process.execPath} ${__filename} child`;
const options = { maxBuffer: 0 };
const child = cp.exec(cmd, options, common.mustCall((err, stdout, stderr) => {
// Verify that if ChildProcess#kill() throws, the error is reported.
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what if it throws because the child exited, wouldn't that be success?

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I'm not sure that I understand the question. Do you mean if Node decides to kill the child process, but in the interim it exits on its own? If exithandler() runs (via the close handler for example), then the error won't be reported because it contains a check to make sure it doesn't run twice.

FWIW, this is the code path being tested.

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node could decided to kill the child, but between when it decided and the child is killed, the child can exit. It would be possible to special case

node/lib/child_process.js

Line 265 in 3268863

ex = e;
for ESRCH, and not call exit handler in that case, because it just means that node has not yet epolled the exit status, but it will in the next tick or so. But the event ordering of the timeout vs the process exit is indeterminate by nature, so its no big deal.

assert(/^Error: mock error$/.test(err));
assert.strictEqual(stdout, '');
assert.strictEqual(stderr, '');
assert.strictEqual(child.killed, true);
}));
}