esrap

Parse in reverse. AST goes in, code comes out.

Usage

import { print } from 'esrap';

const { code, map } = print({
  type: 'Program',
  body: [
    {
      type: 'ExpressionStatement',
      expression: {
        callee: {
          type: 'Identifier',
          name: 'alert'
        },
        arguments: [
          {
            type: 'Literal',
            value: 'hello world!'
          }
        ]
      }
    }
  ]
});

console.log(code); // alert('hello world!');

If the nodes of the input AST have loc properties (e.g. the AST was generated with acorn with the locations option set), sourcemap mappings will be created.

Options

You can pass the following options:

const { code, map } = print(ast, {
  // Populate the `sources` field of the resulting sourcemap
  // (note that the AST is assumed to come from a single file)
  sourceMapSource: 'input.js',

  // Populate the `sourcesContent` field of the resulting sourcemap
  sourceMapContent: fs.readFileSync('input.js', 'utf-8'),

  // Whether to encode the `mappings` field of the resulting sourcemap
  // as a VLQ string, rather than an unencoded array. Defaults to `true`
  sourceMapEncodeMappings: false,

  // String to use for indentation — defaults to '\t'
  indent: '  ',

  // Whether to wrap strings in single or double quotes — defaults to 'single'.
  // This only applies to string literals with no `raw` value, which generally
  // means the AST node was generated programmatically, rather than parsed
  // from an original source
  quotes: 'single'
});

TypeScript

esrap can also print TypeScript nodes, assuming they match the ESTree-like @typescript-eslint/types.

Why not just use Prettier?

Because it's ginormous.

Developing

This repo uses pnpm. Once it's installed, do pnpm install to install dependencies, and pnpm test to run the tests.

License

MIT