Wednesday, 17 April 2013

The Go Language - My thoughts

I've been using the Go programming language for almost three months now pretty much full time. I have moved from the Desktop Experience team working on Unity, into the Juju team. One of the main reasons I moved was to learn Go. It had been too long since I had learned another language, and I felt it was better to dive in, than to just mess with it on my own time.

A friend of mine had poked around with Go during a hack fest and blogged about his thoughts. This was just before I really started poking around. Interestingly the main issues that Aldo found frustrating with the errors for unused variables and unused imports, I have found not to be such a big deal. Passingly griping, sure, but not a big issue. Having the language enforce what is often a lint checker in other languages I see as an overall benefit. Also, even though I don't agree with the Go formatting rules, enforced by gofmt, it doesn't matter. It doesn't matter because all code is formatted by the tool prior to commit. As an emacs user, I found the go-mode to be extremely helpful, as I have it formatting all my code using gofmt before saving. I never have to think about it. One thing I couldn't handle though, was the eight character tabs. Luckily emacs can hide this from me.

;; Go bits. 
(require 'go-mode-load)
(add-hook 'before-save-hook #'gofmt-before-save)
(add-hook 'go-mode-hook (lambda () (setq tab-width 4)))
There are some nice bits to Go. I very much approve of channels being first class objects, and the use of channels to communicate between concurrently executing code. Go routines are also nifty, although I've not used them too much myself yet. Our codebase does, but I've not poked into all the nooks and crannies yet.

However there are several things which irritate the crap out of me with Go.

Error handling

The first one I guess is a fundamental design decision which I don't really agree with. That is around error handling being in your face so you have to deal with it, as opposed to exceptions, which are all to often not thought about. Now if our codebase is in any way representative of Go code out there, this is just flat out wrong. The most repeated lines of code in the codebase would have to be:

if err != nil {
  return nil

This isn't error handling. This is just passing it up to the chain, which is exactly what exception propagation does, only Go makes your codebase two to three times larger due to needing these three lines after every line of code that calls into another function. This is one thing I really dislike, but unlikely to change.

As a user of a language though, there are other things that could be added at the language level to make things slightly nicer. Syntactic sugar, as it is often known, makes the code easier to read.

If the language is wanting to keep the explicit handling of errors in the current way, how about some sugar with that.

Instead of

func magic() (*type, error) {
    something, err := somefunc("blah")
    if err == nil {
        return nil, err
    otherThing, err := otherfunc("blah")
    if err == nil {
        return nil, err
    return foo(something, otherThing), nil 

we had some magic sugar, say a built-in method like raise_error, which interrogated the function signature, and returned zeroed values for all non-error types, and the error, and returned only non-error values, we could have this

func magic() (*type, error) {
    something := raise_error(somefunc("blah"))
    otherThing := raise_error(otherfunc("blah"))
    return foo(something, otherThing), nil 

The range function

There are several different issues I have with the range function.
  1. range returns one or two parameters, but the language doesn't allow any user defined functions to return one or two parameters, range is super special
  2. using range with a slice or array and getting a single value, doesn't give you the value, but instead the index - I never want this
  3. there is no way to define range behaviour for a user defined type
These three things are mostly equal in annoyance factor. I'd love to see this change.

No generics

Initially I accepted this as a general part of the language. Shouldn't be a big deal right? C doesn't have generics. I guess I spent too long with C++ then.
My first real annoyance was when I had two integers, and I wanted to find the maximum value of the two. I go to look in the standard library and find math.max. However that is just for the float64 type. The standard response from the team was "it is only a two line function". My response is "that's not the point".

Since there is no function overloading, nor generics, there is no way with the language at this stage to make a standard library function that determines the maximum value of two or more numeric types, and return that maximum in the same type as the parameters. Generics would help here.

A second case for generics is standard containers. The primary container in Go at this stage is the map. So many places in our codebase we have map[string]interface{}. The problem with this is that you have to cast all values retrieved from the map. There is also no set, multi_map, or multi_set. Since there is no way to provide simple iteration for user defined types, you can't easily define your own set type and have simple iteration using range.

Interfaces that aren't explicitly marked as being implemented help in some ways to provide features provided by generic types and functions, but it is a poor substitute.

So far...

Learning Go has been an interesting experience so far. I like learning new things, and I'm going to be using Go for some time now with the current project. No doubt I'll have more to write about later.