Minor coding issue: fs.exists[Sync]() fs.stat() fs.access() immediately BEFORE fs.openFile() or fs.read/writeFile()

[danielweck]

https://nodejs.org/api/fs.html

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Using fs.stat() (etc.) to check for the existence of a file before calling fs.open(), fs.readFile() or fs.writeFile() is not recommended. Doing so introduces a race condition, since other processes may change the file's state between the two calls. Instead, user code should open/read/write the file directly and handle the error raised if the file does not exist. In general, check for the existence of a file only if the file won’t be used directly, for example when its existence is a signal from another process.

Now, in practice in both Thorium and the r2-xxx-js components, there is no possible scenario where separate processes can potentially access the same resource "at the same time", in such a way that this would cause the aforementioned race condition. In other words, there is no possibility of a microtask tick between fs.exists() and fs.readwrite() in the I/O event queue resulting in fs.exists() being invalidated.

That being said, good coding practice should be followed and I think we should review the code that deals with file access in our codebase(s). https://github.com/edrlab/thorium-reader/search?q=fs.existsSync

[danielweck]

An issue worth keeping alive, but as a developer discussion until it is actionable more broadly in the codebase.