Show HN: ts-remove-unused – Remove unused code from your TypeScript project

Will it remove exports that are only imported for the sake of testing? Eg: it is only imported by files ending in .test.ts or with __test__ as a parent directory?

I’ve tried tools like this in the past within projects that have high test coverage but I have never had any luck because of this edge case.

kazushisan · a year ago

I may be opinionated but I believe that the best practice is to configure a separate tsconfig for test files with project references. As long as the test files are not included in the tsconfig passed to ts-remove-unused, it should remove exports that are only used in test files.

https://www.typescriptlang.org/docs/handbook/project-referen...

rickcarlino · a year ago

In the JavaScript API, it would be nice if there was the ability to have custom comparative functions for this sort of use case. A user defined function that gets called right before final output which allows the user to create custom filtering rules and return a boolean to indicate inclusion or exclusion. I could see this being useful not only for the case I just presented, but also other cases such as NextJS projects that export default functions in pages that are never imported elsewhere in the project.

3523582908 · a year ago

hey! I was wondering if you'd be willing to explain what project references are and why you would do test config this way?

rty32 · a year ago

I think this can get very nuanced --

If you are providing a library, it's possible you are exporting a function that is meant to be used by downstream code, and that function is isolated from other parts of the code (so never used by other functions but only tests)

If you are writing "product" code, most likely this is just dead code. But there are also edge cases where a function is used as the entry point for other code outside the current repository etc.

Put it this way -- if you are given a codebase you have never seen before, and you see a function only imported by test on the first day. Would you remove it without hesitation? Probably not.

I feel this is likely something that must require human experience to be done "correctly".

rickcarlino · a year ago

A custom comparative function that returns true or false based on the special requirements of the project might fix that. I don’t think the project supports this based on a quick look at the documentation but I would love to see this added as a feature.

This is cool, as a place which uses Typescript for a lot of things, including back-end services we handle it differently. Basically we have a rather strict linting process setup which will warn developers of unused code in development environments and outright refuse it for staging deployment and forward. I’m not sure we would “dare” to automatically remove it, because for the most part there is a reason it is there. Maybe it’s something that needs to be deleted, but it’s almost always something which needs to be handled in some way.

Unused imports is perhaps the one area where I would be comfortable removing unused imports. I would never personally allow a third party package into our environment for something like this. I really don’t want to be rude about it, but it’s too “trivial” to rely on an external import for. Not because your code couldn’t be better than ours, it probably will be, but because it’s an unnecessary risk.

For smaller or personal projects I think many people will rely on something like prettier to do the same.

kazushisan · a year ago

Thanks for the input! I think there may be a misunderstanding about what this does. Existing linters work great for detecting unused code within a file but once you add `export` to it, you can’t detect unused code with linters even if it’s not referenced from any file.

You’re right that this tool may not be useful for some codebases. If your modules are more like “scripts” that include side effects, deleting modules just because it’s not referenced may break things. That should not be the case for react projects that are based on components.

In our development process, we don’t allow the changes made by this tool to be deployed automatically. Instead we make sure the changes are okay by creating a pull request and reviewing. We treat it more like an assistant that does all the cumbersome clean up work in no time.

worx · a year ago

Could you provide examples of such risks? Because in my understanding, if some function/constant is exported but never imported anywhere, then it must be dead code and never run. And if it was reachable, then TypeScript would fail the compilation. As such, it sounds reasonably safe to me to remove it.

I only see these potential risks:

1. Using a mix of TS/JS and having some blind spots where we could accidentally delete non-dead code without the compiler noticing.

2. Having and relying on side effects. For example, `export const foobar = thisFnWillDoSthImportant()` and then, yes, removing that would break things.

3. Having separate projects/libs where some consumer might be accessing your exports directly.

Do you see other risks than those?

koolba · a year ago

> Could you provide examples of such risks?

The risk is adding yet another dependency controlled by a third party that executes on your developer’s local machines and on your CI system.

rarkins · a year ago

I tried it on https://github.com/renovatebot/renovate

It deleted 100s of files, most of which were Jest test files, and potentially all of which were a mistake. I restored them all with `git restore $(git ls-files -d)`.

I then ran `tsc` on the remaining _modified_ files and `Found 3920 errors in 511 files.`

Obviously at that point I had no choice but to discard all changes and unfortunately I would not recommend this for others to even try.

You need a valid tsconfig that defines the scope of the project and it seems renovate’s tsconfig doesn’t meet this requirement. You can always --skip manually as an alternative option.

Renovate's TS tooling seems to work fine otherwise, and for ts-remove-unused as a new tool wanting to get adoption then you should be aiming to work the way your users already work, and not fail + tell them that they are the ones which need to change.

BTW the VSCode extension which someone else linked to discovered everything perfectly, which is another hint that your tool needs to improve, not your users.

Even if tsconfig.json was very important, and the users are all wrong and you're right, the only thing your readme says is: "The CLI will respect the tsconfig.json for loading source files." which is insufficient.

_jayhack_ · a year ago

This is simple and configurable with Codegen - see the results on `renovate` here: https://www.codegen.sh/codemod/4553/public/diff

Most transformations like this are not possible with pure static analysis and require some domain knowledge (or repo-specific knowledge) in order to pull off correctly. This is because some code gets "used" in ways that are not apparent i the code.

Enjoy!

fkyoureadthedoc · a year ago

yeah the `--check` option should be the default mode imo

zlies · a year ago

You should switch the default to not delete any files and modify/remove the files only with some flag (--dry-run=false, --rm, --delete, etc). I just deleted all files accidentally in a monorepo :D Luckily I didn't had any uncommitted changes and could recover using git

jamil7 · a year ago

It's maybe reasonable to change the defaults, but I think you should also be mindful of running any random cli program in your codebase, the top of the Github readme does indicate that the --check mode runs it without deleting files.

richardw · a year ago

I’d maybe recommend inverting the command so it doesn’t delete by default but only when you add the relevant flag. Far better to add a little rigmarole than deal with a sad person who wiped their code.

You're totally right. I just quickly scanned the readme and had expected a tool that only check the files. But yes, it's a bad idea in general to run random cli programs without checking them in detail

filleokus · a year ago

It would be kinda cool to use git status to avoid accidental data loss for tools like this.

I've never interacted with git programatically so I don't know how messy it would be to implement. But for tools that mostly operate on "whole files" rather than lines in files, I guess it shouldn't be that tricky?

umanwizard · a year ago

It’d be very easy to programmatically check which files in a repo directory are unknown to git. Git status does indeed have a machine-parseable output mode.

Dead Comment

I tried it and it's pretty cool, I might introduce it in our company project. I did notice one problem/caveat: It doesn't play nice with dynamic imports. Our project has a few files being lazily imported and the tool seems to think that those files are unused, which is not true, they're just imported with the `import('./file')` syntax.

But other than that it's pretty nice, I might look into the code to see if I can help with that small bug.

_fat_santa · a year ago

I've been using ts-prune[1] for years at this point. The project is in maintenance mode but works fine so I've kept using it. I've been looking into Knip[2] which is recommended by the authors of ts-prune though it's been slow mostly because there's little incentive with the current tool working fine.

[1]: https://github.com/nadeesha/ts-prune

[2]: https://github.com/webpro-nl/knip

bikitan · a year ago

I was in a similar spot, but knip offers more information that ts-prune, and ts-prune may trip on some newer TS syntax. I've been happy using knip so far.

ditegashi · a year ago

Deleted 80% of my project. Glad I could revert it but yeah pretty useless at this point

joseferben · a year ago

really nice that you're tool focuses on removing. i've been using https://knip.dev/ for detection in monorepos, but it's cumbersome to remove manually.

Cannabat · a year ago

Knip does have some auto fix capabilities but it’s not perfect yet. The detection is great, though. I use it with `dpdm` to keep things tidy. With these (plus eslint, prettier and typescript) in CI, I feel all warm and fuzzy.

OP, can you describe differences from knip?

My understanding is that Knip is for detecting unused things and that it's auto-fix feature is still experimental, but with that out of the way...

- In general, I personally do not like the idea of having to add another config file in my repo. I feel it's contradictory that I need to add more to my codebase to clean up the clutter in my codebase. I understand that relying on tsconfig to specify the target files has its pros and cons but I hope that my tool will encourage users to maintain their tsconfig. - Knip has its own ecosystem around removing unused stuff in your codebase (not limited to exports). I personally prefer tools that are more single-purposed and does one thing right so I don't have any ideas for expanding features; It will be focused on auto-fixing unused code caused by unncessary `export`s.

devjab · a year ago