Jake Worth

Make Renames Easy

Published: March 22, 2022 3 min read

“There are only two hard things in Computer Science: cache invalidation and naming things.” — Phil Karlton

Today I want to talk about re-naming things, because names are hard. Worse than a bad name is sticking with it because you can’t or are afraid to change it. I want to argue that you should effortlessly and fearlessly fix bad names.

What’s a bad name? Here’s an example, a function called longName:

function longName() {
  if(useLongName) {
    return `${this.firstName} ${this.lastName}`
  } else {
    return this.firstName[0]
  }
}

A few issues that I have:

  • longName is probably often wrong. If configuration tells us useLongName is false, then we don’t return a long name, we return a letter.
  • What’s ‘long’? Could we say ‘full name’?

I’m not sure what the best name might be because we don’t have much context. But longName isn’t it.

I wrote about this in ‘Pick a Good Name’:

“Bad names make it difficult to search through the code. They make it difficult to talk about the code, because the name confers inaccurate meaning, or no meaning. They make it difficult to refactor or change behavior, because the name becomes a handle. Like a handle on a basket, when you’ve mentally reached for it enough times in a certain way, you become trained to do that forever.”

So, what’s the solution? As Sandi Metz said: “You’ll never know less than you know right now.” Sometimes we don’t pick the perfect name the first time. And so we must rename, effortlessly and fearlessly.

Every text editor needs a great search and replacement feature. We should be able to change every instance of a name in a file without much effort. When it’s hard or risky, people won’t do it.

In my Vim configuration, I have a mapping courtesy of my Hashrocket colleague Vidal. It takes the word under a cursor in visual mode and puts it into command mode in a replacement command.

vnoremap <c-r> "hy:%s/<c-r>h//gc<left><left><left>

So, if I have the word “longName” under my visual cursor and execute c-r, I’ll enter command mode with my cursor on the replacement portion of the command:

:%s/longName//gc

With this mapping, I mindlessly rename all the time. Goodbye, longName.

Changing names across files is harder in Vim than in other editors. That’s why I try to do it as soon as I think I should, when the pain is small. Figure out how to do it in your editor, and do it.

Changing file names should be similarly easy. I use vim-eunuch to apply the :Rename command from Vim. This is one situation where good tests or types are irreplaceable. If you change a filename that’s referenced by any of your other files, your tooling should be screaming.

I lean more into names than many developers. A while ago, I decided that I wanted to use named JavaScript exports rather than default exports. So I started to change these:

// Example.js
export default Example = () => <div />

// other file
import Whatever from 'Example'

To this:

// Example.js
export const Example = () => <div />

// other file
import { Example } from 'Example'

I prefer this style because it:

  • Makes searching and refactoring easier
  • Encourages me to choose good component names
  • Allows me to jump to the component definition via Ctags

Is there a time when you can’t rename? Rarely. In highly coupled designs, renames can be painful. But often the folks opposing a rename aren’t in these unusual cases. They’re afraid of breaking something or appearing to question their previous choices.

The more time bad names are allowed to remain, the more damage they do. Whenever you parse a bad name and figure out what it’s really doing, you’ve done hard work that you should spare future developers from. Make renames one of the easy things, and you’ll be a programming hero.

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