Add no-reassign-params

[elicwhite]

Adding this codemod because someone from open source might be interested in fixing the shadowing issue that keeps us from using this at Facebook.

A test for the issue we have at Facebook is commented out in the test file:

  // Shadowing function argument
  // This doesn't work yet and is the major blocker to us being able to
  // use this at Facebook.
  defineInlineTest(
    transform,
    undefined,
    `
function foo(x) {
  x = 2;
  var x = 4;
  return x;
}`,
    `
function foo({x}) {
  let localX = x;
  localX = 2;

  var localX2 = 4;
  return localX2;
}`,
  );

Reasonable to merge this in the mean time for others to get value. Most people don't run into this edge case.

[klvs]

Full disclosure: I'm not codemod expert. Infact, I've never used jscodeshift so my solution might naive or plain wrong. It seems like interesting tech so I figured I'd give it a shot.

Anyway, I roughly have this working but am wondering if the object destructuring in the param for the test is intentional. i.e: function foo({x}) { should be function foo(x) {, no? Otherwise the codemod would be changing the signature which would be bad, right?

If not I'm probably misunderstanding something. If so, then I nearly have this working -- just need to clean it up and fix a test case I broke.

[elicwhite]

Whoops. Yep! The result should be function foo(x) {. Good catch. Sorry for adding some confusion to your first foray into codemods. :)

[elicwhite]

@klvs, I'm really excited for your fixes. I actually keep checking my github notifications hoping to see something from you. That is how excited I am. :P

Let me know if you have any questions that I can help you resolve.

[klvs]

Oh okay. I'll open up a WIP soon. Took a little break but I'll send a PR your way in the next day or two. Thanks for the support.

[elicwhite]

@klvs Anything I can do to help you be successful with this? :)

[klvs]

Not particularly. My classes caught up with me and I plan on finishing this (if it's not done) when they're done. I can put up a WIP PR if you'd like but the code is currently kinda hacky.