Prettier ESLint CLI

Common errors

• Error: Cannot find module 'prettier-eslint'

  cause The `prettier-eslint` package, which provides the core formatting and fixing logic, is a required peer dependency but is not installed in your project.
  fix Install `prettier-eslint` explicitly in your project: `npm install prettier-eslint` or `yarn add prettier-eslint`.

• Error: Minimum Node.js version not met. Expected >=16.10.0 but got vX.Y.Z

  cause The installed Node.js version is older than the minimum requirement for `prettier-eslint-cli` v8.0.0 and above.
  fix Upgrade your Node.js runtime to version 16.10.0 or newer. You can use tools like `nvm` (`nvm install 18 && nvm use 18`) or `volta` (`volta install node@18`).

• Formatting error: Some files could not be formatted. This may indicate an issue with your Prettier or ESLint configuration.

  cause This often occurs when there's an unresolvable conflict between Prettier's formatting and ESLint's auto-fix rules, or if there are syntax errors in the input files that prevent successful parsing by either tool.
  fix First, run Prettier and ESLint separately (`prettier --check <files>` and `eslint --fix <files>`) to pinpoint which tool is failing. Then, review your `.prettierrc` and `.eslintrc` files for conflicting rules or syntax errors in the processed code. Ensure `eslint-config-prettier` is properly configured.

• Command not found: prettier-eslint-cli

  cause The `prettier-eslint-cli` binary is not located in your system's PATH, or the package is not installed globally, or it's not accessible via `npx` from your current directory.
  fix Ensure the package is installed in your project (`npm install prettier-eslint-cli --save-dev`) and always run it using `npx prettier-eslint-cli`. If you want to use it globally, install it with `npm install -g prettier-eslint-cli`.

Warnings

• breaking Version 9.0.0-alpha.0 introduces explicit support for ESLint v9's new flat configuration system (`eslint.config.js`). Projects still relying on the legacy `.eslintrc` configuration format may encounter compatibility issues and should either update their ESLint setup or remain on `prettier-eslint-cli` v8.
  Fix: If migrating to ESLint v9, update your project's ESLint configuration to the flat config format. If staying on legacy ESLint configurations, use `prettier-eslint-cli` v8 or earlier.
• breaking Version 8.0.0 dropped support for Node.js versions older than 16.10.0. Attempting to run `prettier-eslint-cli` v8 or newer on unsupported Node.js versions will result in runtime errors.
  Fix: Upgrade your Node.js environment to version 16.10.0 or higher. Tools like `nvm` or `volta` can assist in managing multiple Node.js versions.
• breaking Version 7.0.0 included significant dependency bumps and internal refactorings. While the CLI was updated to better handle the `prettier-eslint` peer dependency, users might still need to ensure `prettier-eslint` is explicitly installed to avoid functionality issues.
  Fix: After upgrading to v7, explicitly ensure `prettier-eslint` is installed as a direct or peer dependency in your project: `npm install prettier-eslint`.
• gotcha Conflicting Prettier and ESLint configurations are a common source of issues, potentially leading to inconsistent formatting, unexpected errors, or even infinite formatting loops if rules continuously revert each other's changes.
  Fix: Carefully audit your `.prettierrc` and `.eslintrc` files. Use `eslint-config-prettier` to disable all ESLint rules that conflict with Prettier, allowing Prettier to be the sole source of truth for formatting.

Install

• npm install prettier-eslint-cli npm
• yarn add prettier-eslint-cli yarn
• pnpm add prettier-eslint-cli pnpm

Imports

• prettier-eslint-cli (binary)
  wrong:

  import { format } from 'prettier-eslint-cli'

  correct:

  npx prettier-eslint-cli --write 'src/**/*.js'

  This package is a command-line interface; it does not export a direct JavaScript API for programmatic use. For programmatic interaction, refer to the `prettier-eslint` package directly.
• Configuration options
  wrong:

  const config = { printWidth: 80 }; prettierEslintCli.format(code, config);

  correct:

  npx prettier-eslint-cli --print-width 80 --single-quote --write 'src/**/*.ts'

  CLI options are passed as command-line flags. Consult the official documentation for a complete list of available flags and their usage.
• Glob patterns
  wrong:

  npx prettier-eslint-cli src/index.js,src/utils.js

  correct:

  npx prettier-eslint-cli 'src/**/*.{js,ts}' 'test/**/*.test.js'

  Multiple files and glob patterns should be space-separated arguments. It is crucial to quote glob patterns to ensure they are interpreted correctly by your shell instead of being expanded prematurely.

Quickstart

This script demonstrates how to set up `prettier-eslint-cli` in a project, including installing its peer dependencies and creating minimal configuration files. It then uses `npx prettier-eslint-cli` to format and fix both JavaScript and TypeScript files, showing the before-and-after content.

#!/usr/bin/env bash

# Create a directory and some dummy JavaScript and TypeScript files
mkdir -p src
echo "const foo = \"bar\"; function add(a,b){return a + b;}" > src/file1.js
echo "let x = 10; const myObject = { key: 'value', other: 123 };" > src/file2.ts

# Install the necessary peer dependencies (Prettier, ESLint, prettier-eslint)
# This ensures that prettier-eslint-cli has the underlying tools it needs.
npm install --save-dev prettier eslint prettier-eslint

# Optionally, create minimal configuration files for prettier and eslint
# .prettierrc.json
echo '{"singleQuote": true, "semi": true, "printWidth": 80}' > .prettierrc.json
# .eslintrc.js (using recommended configs for demonstration)
echo 'module.exports = { extends: ["eslint:recommended", "prettier"] };' > .eslintrc.js

# Run prettier-eslint-cli to format and fix the files in place
npx prettier-eslint-cli --write 'src/**/*.js' 'src/**/*.ts'

# Output the content of the formatted files to see the changes
echo "\n--- Formatted src/file1.js ---"
cat src/file1.js

echo "\n--- Formatted src/file2.ts ---"
cat src/file2.ts

# Expected output for src/file1.js (example, exact depends on config):
# const foo = 'bar';
# function add(a, b) {
#   return a + b;
# }