Comment by aw1621107
16 hours ago
> In both cases getting no owner should suffice?
Depends on what exactly you plan on doing with the information, I'd imagine. I don't think it's necessarily a given that "no document" and "no owner" should be handled identically (e.g., searching for the updated document to try again vs. returning an operation-not-allowed error).
> Why are you using get_owner to try and figure out if the document exists?
Potential TOCTOU issues, perhaps? As I mentioned the document could have vanished out from under you so detecting this situation could let handle things appropriately (though to be fair that argument could probably extend to future operations as well).
Maybe a versioned filesystem would have made a bit more sense, where None would indicate a new version is available? Another example I've seen mentioned is trying to get a key-value pair from a JSON where the key may be missing.
But in any case, I did say it was a bit of a contrived example, so cut me a bit of slack :P It was just the first thing that came to mind.
The examples sibling comments give are probably more practical.
> I don't think it's necessarily a given that "no document" and "no owner" should be handled identically (e.g., searching for the updated document to try again vs. returning an operation-not-allowed error).
If you care whether a document exists or not, you should use an API that exclusively tells you that instead of expecting everything related to documents telling you if the document exists or not. Otherwise you’re overloading the meaning. A non existent document has no owner. An API to fetch the owner of the document should not care if it exists or not, it does not matter.
As I said, that sounds like a recipe for potential TOCTOU errors.
But again, this was an off-the-cuff example that I explicitly described as contrived from the start. I could probably flesh it out to make more sense, but I think it'd be easier just to refer to sibling comments rather than bikeshed this to death.
Not really? It returns no owner if the document is deleted or just does not exist, which is accurate. Why do you need get_owner to tell you if the document exists or not? If anything it should be an error if the document doesn’t exist because you’ve violated a precondition.
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