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War is over, if you want it

War is over now

– Lennon

Have you been a belligerent in the code-formatting wars? Do you have strong opinions on tabs vs. spaces or on the merits of The One True Brace Style over other indentation styles?

Something has now changed that renders these wars obsolete.

When I joined Google one culture shock was discovering how picky Google was about seemingly trivial details of formatting. Time and again my code reviewers objected to what I thought was my creative expression of coding craft. They were unmoved by my assertion that b*b - 4*a*c was more readable than b * b - 4 * a * c or that FOO was a better name for a constant than kFoo.

Quickly I came to peace with the style guides and recognized their value. I realized that operating in Google’s fabled monorepo I was reading more code than I was writing, making me appreciative of how a consistent style made the code much easier to read. Also as a code reviewer and tech lead I appreciated how just a link to a section of the quasi-legal style guides could cut short tedious bikeshedding on formatting issues and allow us to concentrate on the important issues.

Initially it was a bit tedious getting all the spacing right and remembering all the subtle line-breaking rules.

But over time it got better. First the linting tools improved and covered more of the style guide so that I generally could find and fix all the issues before sending code changes for review.

But then it got even better, with the linting tools supplemented by tools that automatically reformatted code according to the style guide for that language. Now I just basically no longer spend any brain cycles on formatting: I write arbitrary sloppily-formatted code and have it fixed up when I save the file.

The designers of the Go language were Googlers, and they bought into this philosophy. Pretty much all Go code is formatted by the gofmt program, which always reformats to the same standard style.

So when I started a personal JavaScript project I really wanted a JavaScript equivalent to gofmt which enforces a standard style.

In the JavaScript ecosystem, Eslint is the standard linter, which not only can warn against style violations, but can automatically fix them. And what’s more it can go beyond simple indentation and spacing and fix more complex rules (all the ones marked with a 🔧 wrench in the list of rules).

Initially I assumed I would want to use the Google JavaScript style guide and the eslint rules that enforce it. I configured Eslint with

 {
    "extends": [
        "eslint:recommended",
        "google"
    ],
    "env": {
        "browser": true,
        "node": true
    },
    "parser": "esprima",
    "parserOptions": {
        "ecmaVersion": 6,
        "sourceType": "module"
    }
}

However, it was a bit unsatisfying to have a non-trivial config file with various things that need deciding and tweaking. It’s also a bit annoying that it cannot not autofix all the problems it finds, so you still have to manually fix some of them.

Nevertheless it works fine, and produces nicely formatted code like below in standard Google format.

export const newCards = () => {
  const cards = [];
  for (let i = 0; i < 2; ++i) {
    const reversed = (i === 1);
    forEachPhrase((phrase) => {
      const responses = [];
      cards.push({phrase, reversed, responses});
    });
  }
  return cards;
};

But then I discovered standard JS. This has everything a auto style formatter should have. It is really easy to install, has good VS Code support, requires no configuration, and can fix all the problems it finds. It produces code like this:

export const newCards = () => {
  const cards = []
  for (let i = 0; i < 2; ++i) {
    const reversed = (i === 1)
    forEachPhrase((phrase) => {
      const responses = []
      cards.push({ phrase, reversed, responses })
    })
  }
  return cards
}

The most notable difference is that it omits semicolons.

Omitting semicolons is something the JavaScript language allows, but the exact rules for when you can do so have some subtle corner cases that can cause ambiguity and unexpected interpretation of code, so the conventional wisdom has long been to always include semicolons. That’s the view of the Google style guide.

But the standard JS community have decided that the cleaner semicolonless look is preferred and have tackled the corner cases (which are rare) by making sure they are handled by other standard JS rules.

Personally, I don’t care whether there are semicolons or not, but I’m going to stick with using standard JS for my projects as the tooling is better and it looks like it’s gaining momentum in the JavaScript community.

Now of course pretty-printing has existed for a long time. The indent formatter dates from 1976, while text editors and IDEs have long been able to autoformat. But all these pretty-printers have one fatal flaw: they are too flexible, and can be configured with different style options.

The revolutionary novelty of Go’s gofmt, standard JS, and Google’s internal tool is that they have no options. They enforce a single standard style.

The wars are over! Everyone should just use a standard auto-formatter with no options.