Long Names Are Long

June 16, 2016 code dart

One smart thing Google does is rigorous code reviews. Every change, before you can land it, gets reviewed in at least two way. First, someone on the team does a normal review to make sure the code does what it’s supposed to.

But, then, there’s a second layer of review called readability. It makes sure the code is, well, readable: Is it easy to understand and maintain? Does it follow the style and idioms of the language? Is it well-documented?

Dart usage inside Google is cranking up, so I’ve been doing a long ton of these kind of code reviews. As a language designer, it’s fascinating. I get a first-hand view into how people use Dart, which is really useful for evolving it. I have a clearer picture of which mistakes are common and which features are heavily used. I feel like an ethnographer journaling the lives of natives.

But, anyway, that’s not what this is about. Heck, it’s not even about Dart. What I want to talk about is something I see in a lot of code that drives me up the wall: identifiers that are too damn long.

Yes, names can be too short. Back when C only required external identifiers to be unique up to the first six characters; auto-complete hadn’t been invented; and every keypress had to be made uphill, in the snow, both ways; it was a problem. I’m glad we now live in a futuristic utopia where keyboard farts like p, idxcrpm, and x3 are rare.

But the pendulum has swung too far in the other direction. We shouldn’t be Hemingway, but we don’t need to be Tennessee Williams either. Very long names also hurt the clarity of the code where they are used. Giant identifiers dwarf the operations you’re performing on them, are hard to visually scan, and force extra line breaks which interrupt the flow of the code.

Long class names discourage users from declaring variables of that type, leading to massive, gnarly nested expressions instead of hoisting things out to locals. Long method names obscure their equally important argument lists. Long variables are annoying to use repeatedly, leading to sprawling method chains or cascades.

I’ve seen identifiers over 60 characters long. You could fit a haiku or a koan in there (and likely enlighten the reader more than the actual chosen name did). Fear not, I am here to help.

Choosing a Good Name

A name has two goals:

After a name has accomplished those goals, any additional characters are dead weight. Here’s some guidelines I use when I names things in my code:

1. Omit words that are obvious given a variable’s or parameter’s type

If your language has a static type system, users usually know the type of a variable. Methods tend to be short, so even when looking at local variable whose type was inferred, or in a code review or some place where static analysis isn’t available, it rarely takes more than scanning a few lines to tell what type a variable has.

Given that, it’s redundant to put the type in the variable’s name. We have rightfully abandoned Hungarian notation. Let it go.

// Bad:
String nameString;
DockableModelessWindow dockableModelessWindow;

// Better:
String name;
DockableModelessWindow window;

In particular, for collections, it’s almost always better to just use a plural noun describing the contents instead of a singular noun describing the collection. If the reader cares more about what’s in the collection, the name should reflect that.

// Bad:
List<DateTime> holidayDateList;
Map<Employee, Role> employeeRoleHashMap;

// Better:
List<DateTime> holidays;
Map<Employee, Role> employeeRoles;

This also applies to method names. The method name doesn’t need to describe its parameters or their types—the parameter list does that for you.

// Bad:
mergeTableCells(List<TableCell> cells)
sortEventsUsingComparator(List<Event> events,
    Comparator<Event> comparator)

// Better:
merge(List<TableCell> cells)
sort(List<Event> events, Comparator<Event> comparator)

This tends to make callsites read better:

sortEventsUsingComparator(events, comparator);

Is it just me, or is there an echo echo in here here?

2. Omit words that don’t disambiguate the name

Some people tend to cram everything they know about something into its name. Remember, the name is an identifier: it points you to where it’s defined. It’s not an exhaustive catalog of everything the reader could want to know about the object. The definition does that. The name just gets them there.

When I see an identifier like recentlyUpdatedAnnualSalesBid, I ask:

A “no” for any of these usually points to an extraneous word.

// Bad:

// Better:

Of course, you can go too far. Shortening that first example to bid might be a little too vague. But, when in doubt, leave it out. You can always add qualifiers later if the name proves to cause a collision or be imprecise but it’s unlikely you’ll come back later to trim the fat.

3. Omit words that are known from the surrounding context

I can use “I” in this paragraph because you can see this post is by Bob Nystrom. My dumb face is right up there. I don’t need to keep saying “Bob Nystrom” everywhere here (despite Bob Nystrom’s temptation to aggrandize Bob Nystrom by doing so). Code works the same way. A method or field occurs in the context of a class. A variable occurs in the context of a method. Take that context for granted and don’t repeat it.

// Bad:
class AnnualHolidaySale {
  int _annualSaleRebate;
  void promoteHolidaySale() { ... }

// Better:
class AnnualHolidaySale {
  int _rebate;
  void promote() { ... }

In practice, this means that the more deeply nested a name is, the more surrounding context it has. That in turn means it usually has a shorter name. The effect is that identifiers with shorter scopes have shorter names.

4. Omit words that don’t mean much of anything

I used to see this a lot in the game industry. Some people succumb to the temptation to inflate their identifiers by adding Serious Business sounding words. I guess it makes their code feel more important and, by extension, makes them feel more important.

In many cases, the words carry no meaningful information. They’re just fluff or jargon. Usual suspects include: data, state, amount, value, manager, engine, object, entity, and instance.

A good name paints a picture in the mind of the reader. Calling something a “manager” doesn’t convey any image to the reader about what the thing does. Does it do performance evaluations? Give raises?

Ask yourself “Would this identifier mean the same thing if I removed the word?” If so, the word doesn’t carry its weight: vote if off the island.

Applying the Guidelines… to Waffles

To give you a feel for how these rules work in practice, here’s an example that breaks all of these rules. This contrived example is heart-breakingly close to real code I’ve seen in reviews:

class DeliciousBelgianWaffleObject {
  void garnishDeliciousBelgianWaffleWithStrawberryList(
      List<Strawberry> strawberryList) { ... }

We know from the type that it takes a list of strawberries (#1), so let’s cut that out:

class DeliciousBelgianWaffleObject {
    void garnishDeliciousBelgianWaffle(
        List<Strawberry> strawberries) { ... }

Unless our program has foul-tasting Belgian waffles, or waffles of other nationalities, we can drop those adjectives (#2):

class WaffleObject {
  void garnishWaffle(List<Strawberry> strawberries) { ... }

The method is inside a WaffleObject, so we know what it’s going to garnish (#3):

class WaffleObject {
  void garnish(List<Strawberry> strawberries) { ... }

Obviously it’s an object. Everything is an object. That’s kind of what “object-oriented” means (#4):

class Waffle {
  void garnish(List<Strawberry> strawberries) { ... }

There, much better.

I think these are pretty simple guidelines. You may think it’s pointless to worry about this stuff, but I believe that naming things is one of the most fundamental tasks we do when programming. Names are the structure we impose on the formless sea of bits that is computing.