I said no such thing. I said idiomatic Go indicates that you must always make values useful. This is an onus placed on the programmer, not something guaranteed by the language. However, since the Either monad here was said to be introduced to wrap idiomatic Go code, not whatever haphazardly written Go code you happened to find in a SourceForge repository, that is of relevance.
> was rebutted multiple times
Cool. I must not have read it. There was a lot of weird shit in there that had nothing to do with anything. I'm not sure how that would even find relevance to the discussion taking place. I get that first year computer science programs are starting up and you're excited to share what you learned in your first week, but I really don't care. You are not going to tell me anything I haven't heard many times before.
Well, if the Go stdlib is haphazardly written and unidiomatic then I think the burden is on you to demonstrate that idiomatic Go, as per your definition, exists.
>more baseless ad-hominem and ignoring the points
I'll boil it down to one sentence: Go forces programmers to use (T, error) when it is not appropriate, and Go would be better if it did not.
Yeah, the older parts of the standard library are definitely not idiomatic. Lots of functions in the stdlib which return errors don't even return an error type. But, of course they aren't idiomatic. Idiomatacy is emergent. They couldn't possibly have been written idiomatically.
> I'll boil it down to one sentence: Go forces programmers to use (T, error) when it is not appropriate, and Go would be better if it did not.
That may be true, but of no relevance. I can see why I didn't bother reading it. Thanks for clarifying that it would have been a waste of my time.
>That may be true, but of no relevance.
So you agree with this, and it rebuts the entire contents of the first post I responded to. I wonder why you were posting irrelevant, off-topic content yourself. But I'm glad you finally agree that Go isn't flawless.
> If a function returns an error, callers must treat all non-error return values as unspecified unless explicitly documented otherwise
It is absolutely not idiomatic to give any meaning to non-error values under error conditions in the usual case. That is extremely unusual and would be generally confusing.
https://google.github.io/styleguide/go/decisions#returning-e...
Based on what? We have come to see that it is beneficial to make zero values useful. In fact, Go Proverbs even says so. Likewise, we have learned it is useful to return the zero value when you have an error. Most commonly, this means returning nil, which is packed full of all kinds of useful information. Therefore, the T value can be expected to useful if the code is idiomatic.
I'd love to see some real-world code you think is idiomatic, but doesn't return a useful T value when there is an error.
> If a function returns an error, callers must treat all non-error return values as unspecified unless explicitly documented otherwise
This is not at odds with that. This merely warns that not all code you may call will be idiomatic. In fact, if I recall correctly, doesn't os.Open (maybe os.Create) return an invalid file handle in some error cases? The standard library is old and what helped us eventually see what is idiomatic. It is decidedly not idiomatic for the most part. If you rely on a function being written idiomatically, then you are going to run into trouble, as that is not a guarantee (unless the documentation provides such a guarantee).
But in the case of this Either wrapper, it explicitly states it is for use with idiomatic code, not any old code you can throw at it.
And the Go style guide says otherwise: if err is non-nil, you shouldn't even check the other return values. The Go proverbs are just words, it doesn't make them true or even good ideas. When Go proverbs don't agree with how Go code is written, including idiomatic Go code, reality wins over a bad theory. The Go style guide happens to better match real code written by real people, even the people directly responsible for the proverbs.
>I'd love to see some real-world code you think is idiomatic
To be fair, I have been talking about the Go programming language and idiomatic code written in that language. You seem to have a different idea of "Idiomatic Go" from everyone else's. Most of the stdlib, including the newest additions, is idiomatic as judged by other people but evidently not by you.
Yes, it says you cannot trust functions, unless documented, to be idiomatic. Which is reasonable as not all code is idiomatic. The language goes to no lengths to enforce how the code is written in this regard (obviously). But we are talking about code that is known to be idiomatic.
> Most of the stdlib, including the newest additions, is idiomatic as judged by other people but evidently not by you.
1. I don't see how it could be. What is idiomatic emerges from writing code and seeing what works and what doesn't. Most of the stdlib was written in the early days before anyone understood what works best. And, thanks to the go1 guarantee, modifying it now is out of the question.
2. If you believe that the stdlib is idiomatic, then you have to accept that returning an int (-1) to represent an error is idiomatic. The standard library is full of that. Which violates the premise of FP-Go that (T, error) is idiomatic. That is not my claim, that is theirs.
That is not what it says, in fact, it almost says the opposite. It is idiomatic Go to never return useful values if error is non-nil unless explicitly documented. It never affirms your particular, personal, definition of what "Idiomatic Go" is and directly contradicts it.
>If you believe that the stdlib is idiomatic
I believe most of the stdlib is idiomatic Go, especially the newer stuff. Your excuse earlier was that the older stuff in the stdlib isn't idiomatic but the newer stuff is. But the newer stuff doesn't match your personal standards for being idiomatic either. I would challenge you to point to a large body of code that actually matches your definition of idiomatic, I do not think it exists.
No, it is very much written from a consumer perspective. There is known, non-idiomatic, code where relying on T in its error state is problematic, so the guidance is reasonable and logical.
But we're talking about this from the producer perspective. These do not challenge each other and can exist in harmony.
> believe most of the stdlib is idiomatic Go, especially the newer stuff.
I wholeheartedly agree, at least with respect to the newer stuff, and have already said as such. Now this is where, in that newer work which is idiomatic, you point to a good example of where you can find meaningless return values when there is an error.
Clearly the vast majority of the standard library, especially in the newer stuff, does return meaningful values upon error, so we need to identify those which buck the trend if we want to hold it as a counterexample of this being an idiomatic practice.
This is just a lie. It's written about Go and doesn't split its perspectives, the producer should only ever return meaningful non-error values with an error if explicitly documented, and the consumer should only ever expect those when documented.
>you point to a good example of where you can find un-meaningful return values when there is an error.
Okay, skimming the release notes for 1.21. The slog package, brand new in 1.21, contains a MarshalText method (and others, but this is the first I noticed). It returns ([]bytes, err) and it is not documented to be idiomatic as per your personal definition. Therefore, by your interpretation of the style guide and your own personal standards, it is not idiomatic. What's more, a nil/empty slice is potentially valid output from marshaling something, so the slice is entirely useless and must be ignored if err is non-nil. It is not valid to try to "derive meaning" (your terminology) from the slice being nil or not, so it is well and truly useless if err isn't nil.
Moreover, I'll assert that if Either existed in the stdlib, it would return Either[bytes[], err] instead of ([]bytes, err), and it is a limitation of Go that they're using (T, error) which does not offer the appropriate semantics.
>Clearly the vast majority of the standard library, especially in the newer stuff, does return meaningful values upon error
This, too, is simply a lie.
At quick glance, I found three MarshalText implementations in the slog package. Which implementation are you referring to specifically?
And, for what it is worth, none of them return useless values on error, so where do I find the fourth which does?
> This, too, is simply a lie.
Let's hope. I love nothing more than being wrong. That means I get to learn something new! But I haven't found it yet, which is sorrily disappointing. Looking forward to you clarifying the above so we can put this to rest.
>I love nothing more than being wrong.
That's odd, because you've contorted yourself into defending absurd positions based on personal definitions no one else shares, including the Go authors, just to avoid admitting you were wrong. The same Go authors responsible for both the proverbs, which you quote as gospel, and the style guide, which you claim doesn't apply when it's inconvenient because it directly contradicts your claims in plain english.
Is it that you've confused implementation with interfaces? I would have to reject the values if received through the TextUnmarshaler interface, which defines MarshalText, as the implementation being called then becomes unknown, and therefore may not be idiomatic. If I was knowingly working with the three concrete types mentioned above then their function is documented.
> That's odd, because you've contorted yourself into defending absurd positions based on personal definitions no one else shares, including the Go authors, just to avoid admitting you were wrong
I mean, all you have to do is show some code which is reasonably considered idiomatic that does not return a useful value when in an error state and I'll be convinced; something you agreed was pertinent and useful when you brought up MarshalText.
The slog package is definitely reasonably considered idiomatic, so you are on the right track. Now you just need to be more specific at to which MarshalText method you are actually referring to. You called attention to it for good reason, no doubt. All we need, as there is more than one, is to know which one you meant specifically. It is a little odd you didn't do that in the first place, but I'm sure it was an accidental omission.
"That's the point. They are not equivalent, they represent different things" – Oh snap. Well, so much for that silly tangent.
If you want to actually have a discussion, you are going to have to go and understand the discussion that was taking place before you tried to take it in some weird and nonsensical direction. The non-sequitors may be entertaining, maybe even true, but off in la-la land with respect to the conversation taking place.
If your intent is simply to be my personal jester, then by all means, run with it. I'll continue to enjoy the laughs. Most people would pay good money to see an entertainer of this caliber, and you are offering it to me for free! I feel privileged.