Wandering Thoughts archives


Go's proposed try() will be used and that will change how code is written

One of the recent commotions in Go is over the Go team's proposed try() built-in error check function, which is currently planned to be part of Go 1.14 (cf). To simplify, 'a, [...] := try(f(...))' can be used to replace what you would today have to write as:

a, [...], err := f(...)
if err != nil {
   return [...], err

Using try() means you can drop that standard if block and makes your function clearer; much more of the code that remains is relevant and important.

Try() is attractive and will definitely be used in Go code, probably widely, and especially by people who are new to Go and writing more casual code. However, this widespread use of try() is going to change how Go code is written.

One of my firm beliefs is that most programmers are strongly driven to do what their languages make easy, and I don't think try() is any exception (I had similar thoughts about the original error handling proposal). What try() does is that try() makes returning an unchanged error the easiest thing to do. You can wrap the error from f() with more context if you work harder, but the easiest path is to not wrap it at all. This is a significant change from the current state of Go, where wrapping an error is a very easy thing that needs almost no change to the boilerplate code:

a, [...], err := f(...)
if err != nil {
   return [...], fmt.Errorf("....", ..., err)

In a try() world, adding that error wrapping means adding those three lines of near boilerplate back in. As a result, I think that once try() is introduced, Go code will see a significantly increased use of errors being returned unchanged and unwrapped from deep in the call stack. Sure, it's not perfect, but programmers are very good at convincing themselves that it's good enough. I'm sure that I'll do it myself.

This change isn't necessarily bad by itself, but it does directly push against the Go team's efforts to put more context into error values, an effort that actually landed changes in the forthcoming Go 1.13 (see also the draft design). It's possible to combine try() and better errors in clever ways, as shown by How to use 'try', but it's not the obvious, easy path, and I don't think it's going to be a common way to use try().

I am neither for or against try() at the moment, because I think that being for or against it in isolation is asking the wrong question. The important question is how Go wants errors to work, and right now the Go team does not seem to have made up its mind. If the Go team decides that errors should frequently be wrapped on their way up the call stack, I believe that try() in its current form is a bad idea.

(If the Go team thinks that they can have both try() in its current form and people routinely wrapping errors, I think that they are fooling themselves. try() will be used in the easiest way to use it, because that's what people do.)

PS: While Go culture is currently relatively in favour of wrapping errors with additional information, I don't think that this culture will survive the temptation of try(). You can't persuade people to regularly do things the hard way for very long.

Update: The Go team dropped the try() proposal due to community objections, rendering the issue moot.

programming/GoTryWillBeUsedSimply written at 23:36:22; Add Comment

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