Comments Are The Only "Code Smell"

My regular readers (both of them) may notice that my previous article basically disavowed the idea of the "code smell". The term is too often a smug, arrogant, dismissive mantra that serves no meaningful purpose. So why is my very next article dedicated to, what I believe is, an actual code smell?? Well, on one level, I'm more than willing to troll myself from time to time. But on another level, there is really only one aspect of programming that I routinely view as a "code smell": Comments.

You may have heard others parrot the phrase "comments are a code smell". I certainly didn't come up with it and can claim no credit in its creation. But I have come to (almost always) agree with it. And the reason I agree with it really speaks to much deeper ideals about how to code.

Programmer Evolution

Most of us have followed a similar path to "enlightenment". It tends to look something like this:

1. Whatever Works
This whole coding thing is brand new. We don't really have any clue what we're doing. We're usually baffled when our code doesn't work. Even when it does work, we're often somewhat confused about why it works. We have no experience with any aspects of "professional" software development.

In this first stage of evolution, our code may look something like this:

const currSC = () => {
  const db = connect('rt', 'kwqw92klad92;wqed');
  return db.get('amt').from('sc').where('sess = ' + sess.Id);
}

const st = (amt) => {
  return amt * 1.07;
} 

let tot = currSC();
tot = st(tot);

At this stage in our evolution, there is only one standard of "quality": Does it work?? And if anyone tries to point out that some of this might be a biiiiiit obtuse, their objections sound rather silly to us. The code is clearly, obviously, self-explanatory. So why would we waste time with silly comments??

Inevitably, we end up having to revisit our own code. It may be months later. Heck, it may only be weeks later. But at some point, we're staring at our own logic - and it no longer seems so... logical.

2. Comments To The Rescue(?)
This is when we first start getting some of that comment religion. The abbreviations that felt so natural - only a short while ago - have now left our mind. But there's a "fix" for this! The how-to-code gurus tell us to "Use Comments!"

Now that we've seen the downside of writing unintelligible code, the Copious Comment Strategy makes sooooo much more sense. And all of the talking heads hail it as the mark of a good programmer. So... we dive in. Head friggin first. And we typically end up with something like this:

// gets the current shopping cart total, based on the user's session ID
// returns a number for the current total
const currSC = () => {
  // connect to database
  const db = connect('rt', 'kwqw92klad92;wqed');
  // find any saved shopping cart total in the 'amt' column in the 'sc' table based on session ID
  return db.get('amt').from('sc').where('sess = ' + sess.Id);
}

// calculate sales tax
const st = (amt) => {
  return amt * 1.07;
} 

// retrieve current total
let tot = currSC();
// add sales tax
tot = st(tot);

The pseudo-code above isn't... wrong. I consider it to be somewhat amateurish. And I wouldn't hire someone on my team who wrote code like this. But this approach is at least "functional".

Writing "functional" code is certainly not a bad thing. The bad thing is that far too many programmers reach this second stage of evolution - and they just stop.

Seriously.

If you never evolve past step 1, you'll probably never get hired to do software development. But I've met plenty of guys who've been in this game for many years - and yet, they've never advanced past this level of evolution.

3. Removing The Translator
The problem here is that farrrrr too many coders come to lean on their comments as though they are "translators". The thinking goes like this:

1. The code I've written is hard to understand.
2. So I'll add a bunch of comments to "translate" the code for anyone who reads the code after me.

I sincerely hope you recognize the horrific flaw in that logic. Despite the connotation of the word "code", the simple fact is that most algorithms needn't be ridiculously difficult to understand.

My girlfriend is incredibly intelligent. But she's never been, nor has she ever tried to be, a programmer. Despite this "difference" between us, there are times when I'm aggravated about a particular issue that I'm trying to solve in my code, and she ask asks me what's wrong. So... I show her the code.

And here's the thing: When she looks at my code, she generally understands the underlying concept that I'm trying to solve/accomplish/develop. Even though she's never coded a day in her life. Sure, she doesn't know all the specifics of the language constructs I'm using. But at a high level, she can actually read my code - without actually being a coder at all.

Let me be perfectly clear with this. You might be thinking:

Your non-programmer girlfriend understands your code because comments are written in plain language and can be understood by nearly anyone!

Umm... no. Absolutely not. I rarely use comments. I might have a few lines of comments in a few thousand lines of code. So the fact that she can grasp the workings of my code has nothing to do with comments. It has everything to do with the way that I write my code.

The more "evolved" we become, the more attuned we become to the idea of self-documenting code. I can lay no claim to this concept. It's been floating around programming circles for decades. But even now, in the 2020s, I feel that far too many devs have a poor grasp of this concept.

Think of it like this: If I move to your town and I plan to work in your office for a long time to come, and if I speak English but everyone in your office speaks Russian, should I write all my emails in English and then try to add a whole pile of "translation" notes to every message? Or should I just put in the effort to format the message, originally, in a way that anyone after me is likely to understand it? In other words, should I keep blathering in English and lean on some "translator" to make everyone else understand? Or should I make every effort to start writing my messages in Russian??

We can illustrate some of these translation roadblocks. The pseudo-code above has some glaring issues:

1. Cryptic abbreviations
2. Obtuse function names
3. Magic literals

So if we're going to address those issues in the name of self-documenting code, we could do something like this:

// gets the current shopping cart total, based on the user's session ID
// returns a number for the current total
const getTotalFromShoppingCart = () => {
  // connect to database
  const database = connect(process.env.databaseUser, process.env.databasePassword);
  // find any saved shopping cart total in the 'amt' column in the 'sc' table based on session ID
  return database.get('amount').from('shoppingcarts').where('sessionid = ' + session.Id);
}

// calculate sales tax
const calculateSalesTax = (amount) => {
  return amount * salesTax.florida;
} 

// retrieve current total
const currentTotalInShoppingCart = getTotalFromShoppingCart();
// add sales tax
const currentTotalWithTax = calculateSalesTax(currentTotalInShoppingCart);

This is typically where many devs - even seasoned, experienced devs - look at my code and think:

OMG! Your variables are so longggg! Everything's so verbose! There's no way that I want to code like this!

But "long" is a relative term. Yes, I tend to favor full-word-name variables. And no, I don't necessarily expect you to do the same. But I do expect you to write your code in such a way that it's as self-explanatory as it can be.

In the example above, it's true that I've written some long variable names. And some long function names. But I've also written code that is, IMHO, fairly self-explanatory. You can just... read it. In fact, it's so self-explanatory that the comments now seem rather... silly. They just duplicate what you should already be able to understand just by reading the code.

So if we're really going to turn this into some "level 3" code, there's really no need for any of those comments. This means that, even though my code might feel a little "heavier" as you read through the variable names, this "weight" is counterbalanced by the fact that I don't have to chuck everything full of comments in order for you to understand it. This is illustrated by the readable nature of this:

const getTotalFromShoppingCart = () => {
  const database = connect(process.env.databaseUser, process.env.databasePassword);
  return database.get('amount').from('shoppingcarts').where('sessionid = ' + session.Id);
}

const calculateSalesTax = (amount) => {
  return amount * salesTax.florida;
} 

const currentTotalInShoppingCart = getTotalFromShoppingCart();
const currentTotalWithTax = calculateSalesTax(currentTotalInShoppingCart);

This is why I feel, very strongly, that comments are, in general, a "code smell". Because nearly all comments that I encounter are trying to explain to me what the code is doing.

I shouldn't have to read any comments to understand what your code is doing. I should be able to understand what your code is doing... by reading the code.

I'm sorry (not sorry) if this sounds a bit harsh. But if I have to read your comments to properly grok your code - then... you've probably written some pretty crappy code. Don't write esoteric code and then rely on your comments to tie it all together. Just write some clearer damn code.

When To Comment

At this point, you may be thinking that I demonize all comments. But that's not the case. There is a time and a place to use comments. But like Regular Expressions, comments should be used as a targeted tool. They're powerful, when used properly. But they can also be a sign of something truly wrong in the code.

Here are a few examples where comments don't suck:

IDE Tooling (e.g., JSDoc)
In modern coding environments, there are many instances where the comments aren't designed so much to speak to other coders. Instead, they're written to speak to the IDE. In other words, comments can help our development tools to "hook everything up" and check the data relationships as we code. That would typically look something like this:

/**
 * @returns {number}
 */
const getTotalFromShoppingCart = () => {
   const database = connect(process.env.databaseUser, process.env.databasePassword);
   return database.get('amount').from('shoppingcarts').where('sessionid = ' + session.Id);
}

/**
 * @param {number} amount
 * @returns {number}
 */
const calculateSalesTax = (amount) => {
   return amount * salesTax.florida;
}

const currentTotalInShoppingCart = getTotalFromShoppingCart();
const currentTotalWithTax = calculateSalesTax(currentTotalInShoppingCart);

I'm not always the biggest fan of JSDoc. But I don't generally have any problem with its use. And I understand the service it provides. So if this is how you're using comments, then... great. As long as this is the approach embraced by your team, then it's certainly a valid use of comments.

[Side Note: Don't be that guy - the one who insists on cramming JSDoc notation into all of his code files, even though the rest of the team has consciously eschewed it. Conversely, don't be that guy that refuses to add JSDoc comment blocks to his functions when the rest of the team has settled on it as a standard.]

Not What, But Why
As I've already tried to explain, if your comments tell me what your code is doing, then it's probably some crappy code. But there's a very different use-case to consider: Sometimes, we need to alert others as to why our code is doing what it's doing.

For example, consider the little pseudo-app we've been working with up to this point. Even after we've made things as "clear" as possible with expressive variable/function names, it can still sometimes be a challenge to understand why the code is doing what it's doing. Specifically, let's look at this function:

const calculateSalesTax = (amount) => {
  return amount * salesTax.florida;
} 

Seems pretty simple, right? It accepts a given amount and returns that amount multiplied by Florida's sales tax. But for a sharp coder, this begs a question:

Why have we hardcoded a sales tax number that is only specific to Florida???

If you're accustomed to building hardy, scaleable apps, this bit of hardcoded logic seems... off. In fact, it's the kind of "oversight" that might lead me to spontaneously refactor the code to utilize a lookupSalesTaxRate() function - even if my current task didn't call for it. This is where a well-placed comment can do a world of good:

const calculateSalesTax = (amount) => {
  // The client specifically told us that they only operate in Florida and they have no plans
  // for expansion.  They understand that we will need to rework this if they ever decide 
  // to do commerce outside the state of Florida.
  return amount * salesTax.florida;
} 

IMHO, this is an excellent use of a comment. It basically alerts all future coders that the current logic is not an oversight and should not be changed, unless that change is driven by the client.

To put this in different terms, we can already tell, by simply reading the code, what it's doing. But it's not clear, from the code, exactly why it's doing that. In this case, the comment can be extremely useful.

Conclusion

Last year, I worked in a shop that had PHP code like this:

//foreach
foreach ($items as $index => $item) {

}

I wish I was making that up, but I'm not even kidding. They had comments above basic language constructs, ostensibly to alert you to the fact that those basic language constructs were there. It was no different than putting a STOP AHEAD sign one meter in front of the STOP sign. It was one of the dumbest damn things I've ever seen in a codebase (and that's saying a lot).

Don't be "that guy". Be smart about how you use your comments. And, more often than not... don't use them. At all.