Is there a way to disable rewriting a file?

[codemod-js]

Is there a way to disable rewriting a file?

[kumarharsh]

That's it! Perfect. I couldn't find anything in the readme for it, but it's there in the cli tool. The flag is called --dry. Thanks 👍

[kumarharsh]

I have had similar problems with recast for quite a long time. There are also issues like the LF -> CRLF conversion which recast can't do much about even if it worked well.

I was thinking whether it'd be possible to have a flag which doesn't even call recast on the code, so the file won't even be touched.

[eventualbuddha]

Have you tried it with --dry-run?

[kumarharsh]

Actually, on further thought, I still think there is a significant use-case for not touching unmodified files. Consider that my codemod changes only some files, but the codemod would still overwrite every single file it reads. So the developer will still have to spend additional time to figure out which files to commit, and which ones to checkout.

Would it be possible to add some functionality for the codemod cli to figure out when to overwrite files? For example, if the visitor function explicitly returns false, then don't modify the file.

[eventualbuddha]

So you have a codemod which doesn't alter the AST, but the files are still being modified? I've seen things like that and they're typically bugs in recast. Can you provide a couple examples of the unwanted diffs?

[kumarharsh]

Sure, check out this in ASTExplorer: https://astexplorer.net/#/gist/63a503b3b38c148a06d6438bad35af65/e81a51e13fc87be488af7801bb441351e12f7f91

[eventualbuddha]

This seems to happen even with something as small as this:

class A {
  a = {};
}

which becomes this:

class A {
  a = {};}

Something about reprinting class properties is probably broken in recast. I'll take a look later if I get time (cc @benjamn).

[eventualbuddha]

Closing since, though this remains an issue, the cause of it is not in codemod.