I have written about the Go programming language before. There, I made clear that I (among other things) disagree with Go’s choice to not include a templating mechanism or generic types.

Now, a few months later, I still stand by that but want to provide some evidence as to why I don’t like the choice. What follows is a part of a function from a Go code base that I am contributing to. Rest assured that once I saw this monstrosity I made room in my schedule to simplify it and clean it up (in fact, what you see below has been simplified a bit for this post).

// search the AI-inventory for the object representing the product
invSlotLoop:
for _, invSlot := range aiInv.Slots {
if invSlot.IsObject() {
objectID := invSlot.ObjectID()
// is it the right product?
product, isProduct := aiHan.pool.Product.TryGet(objectID)
if isProduct && product.BlueprintID == job.BlueprintID {
// are all the slots that the current job should install done?
for _, jobSlotIndex := range job.BlueprintSlotIndices {
if !product.IsSlotInstalled(jobSlotIndex) {
continue invSlotLoop
}
}
// all slots done! this is our product!
// get it to one of the output inventories.
productStorable := aiHan.pool.Storable.Get(objectID)

outInvLoop:
for _, outInvEnt := range workplace.OutputInventories {
outInv := aiHan.pool.Inventory.Get(outInvEnt)
for _, outInvSlot := range outInv.Slots {
if outInvSlot.IsEmpty() && outInvSlot.IsCompatible(objectID, productStorable) {
// we have found an inventory where we can put it! walk to the inventory!
hasToWalk, err := aiHan.walkToEntity(aiEnt, outInvEnt)
if err != nil {
// nah, we can't walk to it. have to find another inventory
continue outInvLoop
}
if hasToWalk {
// walking is triggered, wait until he gets there
return
}
// transfer the object
aiHan.invTransferMan.Transfer(aiEnt, outInvEnt, nil, objectID)
}
}
}
}
}
}


The code above should of course be simplified by introducing a few functions that break the nesting and make it easier to follow the flow; there also is some error handling that I do not agree with.

I count a full 7 (!) levels of nesting, including 2 loops with labels and label-targeted continues. Of course, Go does not force you to write your code like this, but it definitely makes it easier and much more attractive for people to do it.

Notice how the first continue targeting the outer most loop is essentially checking whether some predicate ( = !product.IsSlotInstalled) is true for any item in a slice. In another language, we might write something like this:

if job.BlueprintSlotIndices.Any(x => !product.IsSlotInstalled(x)) {
continue
}


In Go, we would have to define Any for each type separately, with its own name like AnyUInt32. Well, it turns out that people don’t really do that. They write out the loop each and every time, because - well - it’s only five lines. The piece of code above shows pretty clearly where this is heading.

Functions serve multiple purposes: Firstly, they should encapsulate commonly used code so that you only have to debug it once etc. Secondly, and more importantly, they should abstract away details. While the details of a simple for-loop should be quite familiar to anyone, there is no arguing that within a function such as the one above a call like xs.Contains(...) would be much easier to parse1 than the equivalent 5-line loop, because there are already so many things going on.

By now, I treat each labeled loop in Go as a pretty serious problem. Heck, even just nested loops are suspicious.

Oh, and this is my version of the function from above (with some additional functionality):

productEntity, ok := getCompatibleFinishedProductInInventory(job, aiInv)
if !ok {
aiHan.tryTakeProduct(aiEnt, job, job.Crafter, true /* take only finished products */)
return
}

result := aiHan.tryStoreObject(aiEnt, productEntity, workplace.OutputInventories)
if result == AIInventoryTransferResultNoSuitableInventory {
aiHan.setNoSpaceFailState(aiEnt, nil)
aiHan.blockWorker(aiEnt)
} else if result == AIInventoryTransferResultNoPath {
aiHan.setNoPathFailState(aiEnt, ecs.InvalidEntityID)
aiHan.blockWorker(aiEnt)
}


1. Also, it would be shorter. I am not convinced that brevity is always a virtue in programming, but some people like Cliff Click argue that the number of bugs created by a programmer is mostly proportional to the lines of code written, not the number of features implemented.