eslint-plugin-no-pipe

An ESLint plugin to disable the use of the pipe operator.

Rule Details

Examples of incorrect code for this rule:

"Hello, World!" |> console.log(%);

Examples of correct code for this rule:

console.log("Hello, World!");

Motivation

The pipeline operator currently sits at Stage 2 as an ECMAScript proposal: https://github.com/tc39/proposal-pipeline-operator

While this proposal was started with the best of intentions, the current iteration (also known as the Hack proposal) is a far stretch from what many people had hoped the pipeline operator would bring. In fact, the proposal is so far-stretched that many people (including me) believe it would be better to have no pipeline operator at all, than the one proposed right now.

This lint rule has two purposes:

• It serves to raise awareness so we can hopefully prevent the proposal from reaching Stage 3 (at which point the proposal can no longer be reversed unless there are serious implementation difficulties).
• If the proposal is accepted, this lint rule will be an unfortunate necessity for people who wish to avoid the pipeline operator in their codebases.

Why you might want to avoid the pipeline operator

The pipeline operator is a potentially useful operator that enables functional composition, and can indeed be used to make a series of operations (a pipeline) more readable in code.

Unfortunately, that's not what the Hack proposal is. Instead, the current proposal is yet another method of doing expression composition. The difference is that Hack is applicable everywhere in the language where expressions can be used, which is indeed almost everywhere. Because of this broad scope, it allows you not only to rewrite console.log("Hello, World!"); as "Hello, World!" |> console.log(%);, but also a[0] as a |> %[0] or 0 |> a[%].

Does it matter? As tools such as Prettier have shown, developers like to avoid bikeshedding over style arguments by delegating such choices to tools. And this is great; by forcing a certain amount of uniformity over code, people have fewer issues reading each other's code. Unfortunately, Hack is about to undo this progress by inventing an alternative expression syntax that permeates the entire language.

How do you define which usages of the pipeline operator are sensible, and which are obviously undesirable? With an operator that is restricted to functional composition, this question can be reasonable scoped. But with the Hack proposal, I see no better way to avoid these arguments than to avoid the operator entirely.

Do you want your child to learn to code using "Hello, World!" |> console.log(%);?

I didn't think so! Please star this repository, and hopefully we can stop the Hack proposal ;)

Further reading

• Effect of Hack proposal on code readability
• JavaScript Pipe Operator Proposal: A Battle of Perspectives

Installation

yarn add -D eslint-plugin-no-pipe

Or:

npm install eslint-plugin-no-pipe --save-dev

Usage

Add no-pipe to the plugins section of your .eslintrc configuration file. You can omit the eslint-plugin- prefix:

{
  "plugins": ["no-pipe"]
}

Then add the rule under the rules section:

{
  "rules": {
    "no-pipe/no-pipe": 2
  }
}