src/pipe-args.js hangs when cml is called from child_process.exec on macOS

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The cursed pipe-args.js file is, again¹ producing esoteric issues on kernels other than Linux: now it hangs forever on macOS when using child_process.exec to run cml --version on iterative/setup-cml#60. 🐇🕳️

$ npm install --global @dvcorg/[email protected]
$ node -e "require('child_process').exec('cml --version', console.log)"

cml/bin/cml.js

Line 85 in 25747f6

.commandDir('./cml', { exclude: /\.test\.js$/ })

cml/bin/cml/publish.js

Line 8 in 25747f6

pipeArgs.load('binary');

cml/src/pipe-args.js

Line 21 in 25747f6

nbytes = fs.readSync(0, buffer, 0, BUFSIZE, null);

cml/src/pipe-args.js

Lines 28 to 30 in 25747f6

	if (err.code === 'EAGAIN') {
	if (process.platform === 'darwin') {
	continue;

Calling fs.readSync throws EAGAIN when there is no data in the standard input, causing an infinite loop in macOS. A similar bug affects Windows, where reading from standard input with no data just hangs readSync forever.

Footnotes

1. https://github.com/iterative/cml/pull/732#issue-1004203281 ↩

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Upstream Issue

• process: process.stdin getter sets O_NONBLOCK flag in open file description nodejs/node#42826