eslint-plugin-esfold

An ESLint plugin which breaks lines when they exceed a specified width, using ESLint’s --fix option.

npm install --save-dev eslint-plugin-esfold

eslint.config.js

import esfold from 'eslint-plugin-esfold';

export default [
  {
    plugins: { esfold },
    rules: { 'esfold/breaks': ['error'] },
  },
];

What it does

At maxWidth: 80, this line measured at 90 columns

const result = computeThing(firstArgument, secondArgument, thirdArgument, fourthArgument);

becomes

const result = computeThing(
  firstArgument,
  secondArgument,
  thirdArgument,
  fourthArgument
);

Pair it with @stylistic/comma-dangle if you want a trailing comma.

Fix types

• overWidth — the line exceeds maxWidth and contains valid potential breaks.
• necessaryBreak — a line contains syntax which must be followed by a break regardless of width, e.g. blocks, classes, statement boundaries or nested JSX elements.
• inconsistentGroup — a group has line breaks applied inconsistently, e.g. an array which does not have breaks for each elements.
• joinable — with join: true, a fully broken group fits on one line.

Options

Option	Default
maxWidth	80	Columns a line may occupy.
tabWidth	2	Columns a tab advances to. Matters only for tab-indented files.
join	false	Also join a fully broken group back onto one line when it fits.

import esfold from 'eslint-plugin-esfold';

export default [
  {
    plugins: { esfold },
    rules: { 'esfold/breaks': ['error', { maxWidth: 80, tabWidth: 2 }] },
  },
];

Usage with other rules

The fold plugin attempts to coexist with other rules. Indentation and other settings are inferred from the file. The plugin also respects newline preferences encoded in other rules like @stylistic/operator-linebreak, dot-location and comma-style, so that the rules jointly resolve within a single --fix run.

Fold does not attempt to provide a 1-to-1 canonical representation of the program, and by default preserves line breaks which are consistently applied.

Joining lines

With join: true, width alone decides the layout: a group broken one element per line is joined back onto one line when it fits.

const point = {
  x: 1,
  y: 2,
};

becomes

const point = { x: 1, y: 2 };

A dangling comma goes with the breaks, and a leading | or & in a broken union or intersection type goes too. A group containing a blank line or a comment keeps its layout, as do interface bodies and anything that must break, like a block. Rules that force breaks, such as @stylistic/array-element-newline: always, fight with join and should not be combined with it.

Requirements

ESLint 9 or later.

License

MIT