Splitting the API and the CLI

I use the jquery-like API for transforming outside of the CLI (FWIW I use it in rollup).

Currently, my hacky workaround (along with some changes in my fork: https://github.com/mikob/jscodeshift) looks like this:

await JSCodeShift('/transforms/split.ts', [`dist/tmp/${pluginName}.joined.mjs`], {
        transform: './transforms/split.ts',
	verbose: 2,
	runInBand: true,

	dry: false,
	print: false,
	babel: true,
	extensions: 'js,mjs',
	ignorePattern: [],
	ignoreConfig: [],
	silent: false,
	parser: 'babel',
	stdin: false
});						

This is not ideal because I get CLI output, a pool of workers, filesystem R/W etc. I’m only interested in using the API internally. So I can do something like this:

const transformedSrc = await JSCodeShift([transformFn: (jscodeshift: JSCodeShift) => string], src: string);

Currently transforms have a function signature like this: module.exports = function (fileInfo: FileInfo, api: JSCodeshift, options) {

With the separated API, I would expect to be able to call a transform and only pass it the 2nd argument.

Related: https://github.com/facebook/jscodeshift/issues/179

[marcusrbrown]

I believe I came up with what you were looking for. The default jscodeshift export is the object passed as the api argument to a transform module from the Runner. If you don’t wan’t any of the Runner functionality, just use jscodeshift directly, however you’d like:

const jscodeshift = require('jscodeshift');

const source = `
function foo() {}

module.exports = foo;
`;

const transform = (j, source) =>
  j(source)
    .find(j.Identifier)
    .replaceWith(p =>
      j.identifier(
        p.node.name
          .split('')
          .reverse()
          .join('')
      )
    )
    .toSource();

console.log(`Original source =\n${source}\n`);

const transformedSource = transform(jscodeshift, source);

console.log(`Transformed source =\n${transformedSource}\n`);

Here I’ve defined my own transform function that does what the sample/reverse-identifiers.js does: reverse all identifiers in the given source.

Running this example produces the following output:

Original source =

function foo() {}

module.exports = foo;


Transformed source =

function oof() {}

eludom.stropxe = oof;

If you want to specify transform modules from files, then I recommend reusing the code in Worker.js, lines 78-81:

  transform = typeof module.default === 'function' ?
    module.default :
    module;

I’ve provided the sample here: https://github.com/igetgames/jscodeshift-demo. Let me know if you need any more information.

[mikob]

@igetgames yes, that’s great! Much simpler than I imagined! Thank you for the very detailed write up!