babel/parser生成ast后，马上用babel/generator输出，结果不一致

Question

const { parse } = require('@babel/parser')
const generator = require('@babel/generator')

const source = `const babel = {
  version() {},
  author: ''
};`

const ast = parse(source)

console.log(generator.default(ast).code === source) // false

console.log(generator.default(ast).code)
/*
const babel = {
  version() {},

  author: ''
};
*/

One more space after the version function

I slightly modified the implementation of the version function. From the previous FunctionExpression to the current ArrowFunctionExpression , the result is in line with expectations.

const { parse } = require('@babel/parser')
const generator = require('@babel/generator')

const source = `const babel = {
  version: () => {},
  author: ''
};`

const ast = parse(source)

console.log(generator.default(ast).code === source) // true

What should I do to keep them consistent?

Answer 1

Babel is focused on performing transformations to the code from the standpoint of programmatic behavior, so it only makes a small amount of effort to reproduce the original formatting. Given that, this is expected behavior.

In the case you're seeing, it appears that the formatting you expect does not match what your Babel version happens to output. If formatting is important, I'd recommend running the code through prettier afterward to give it consistent formatting.