Fork-ts-checker-webpack-plugin: Suport for noEmitOnError?

[knaos]

Hey guys, is it possible to use the noEmitOnError from tsconfig.json?

[piotr-oles]

Hi! :)
This plugin only checks typing errors and reports errors. There is no emit at all. I think this issue should be opened in ts-loader repository :)

[johnnyreilly]

Although I haven't checked recently, I believe ts-loader already supports this (I think some of our execution tests depend on it).

[johnnyreilly]

I'd close the issue if there's no more to do

[knaos]

Yes, thank you. @johnnyreilly ts-loader has it working. But I want to use it with happypack, and then the emit prevention won't work.

[piotr-oles]

@knaos I just realized what you want to achieve and why it won't work. If you are using transpileOnly mode, ts-loader doesn't know about semantic errors so it's not possible to block emit. The information about errors is in the fork-ts-checker-webpack-plugin.

Support for this setting would be possible only in the "async: false" mode, where type-checking and emitting is synchronized. There is fork-ts-checker-emit webpack's hook - ts-loader could listen on that hook and block emit if there would be errors.

@johnnyreilly what do you think about that?

[johnnyreilly]

Yup - I'd be open to a PR on that :+1:

[eddyw]

@johnnyreilly I'm curious about the status of this issue. Is it now possible to do so?

[johnnyreilly]

Uh I don't think anything has been implemented related to this so I guess not.. don't actually know

[eddyw]

@johnnyreilly I'll try to implement it on ts-loader and open a PR. It will take me some time, because I'm actually hating the hacky way I'm dealing with this right now.

Actually, I was thinking about building a new loader to have accept a function in options to listen to some hooks and decide if it should allow emitting files or not. Kind of:

{ loader: 'some-loader', options: { listen: (done, fail) => { /* decide here if it should allow emitting or not */ } } }

So it could work as a general solution rather than a solution only for ts-loader. Do you know if something like this exists? If so, I won't need to code it haha

[johnnyreilly]

I don't know - now's your chance!

[eddyw]

@johnnyreilly got it working!. Listening to fork-ts-checker-receive hook instead before fork-ts-checker-emit is reached, so it's possible to tell webpack not to emit on error. I will share it tomorrow, now the code is a mess.

[johnnyreilly]

Great!

[eddyw]

@johnnyreilly I wrote what I was using as a webpack loader. It's a bit hacky but works:
https://github.com/eddyw/forktschecker-hook-loader

Maybe something like it could be implemented inside fork-ts-checker-webpack-plugin. I mean, if this package could ship also a loader.

Anyway, it works with my current configuration in build and watch mode. The first build is usually slower in --watch, then it's cached and every other rebuild after it is faster. Also, I actually get better results with async: false (threads: 2, happypack threads: 6)

[eddyw]

It's been some time. I figured how to make the compiler work with HappyPack or thread-loader without killing Type Checking and also allowing to noEmitOnError..
https://github.com/eddyw/owlpkg-typescript-loader

I wrote the loader from scratch. First as part of an experiment, then it turned out to work fairly well. tslint is also able to run within the loader with HappyPack, ... and cache

[vepanimas]

If that line will be invoked before shouldEmit webpack hook, we'll got it working. That's how the default NoEmitOnErrorsPlugin works, it checks compilation.errors on shouldEmit and returns false if they exist.

So if we could move this code to an earlier stage (ex. afterCompile or even shouldEmit), it would possibly fix that issue. @johnnyreilly

[Fatme]

Hey @piotr-oles, @eddyw, @johnnyreilly, @knaos, @vepanimas,

We've hit the same issue and spent some time to investigate it.

@vepanimas,
You're absolutely correct that we'll got it working if we move the logic from emit hook to an earlier stage of webpack compilation. According to the source code in webpack repo, we need to push errors in compilation object before or at the latest on shouldEmit. This way noEmitOnErrors property in webpack.config will work out of the box.

It turns out that shouldEmit is not suitable for our case as it is SyncBailHook but we need AsyncSeriesHook. However, afterCompile seems the perfect solution as it is async hook and is executed before shouldEmit.

[johnnyreilly]

Do you want to raise a speculative PR and let's see where it goes?

[Fatme]

@johnnyreilly,

Here is the PR - https://github.com/TypeStrong/fork-ts-checker-webpack-plugin/pull/337.

[Fatme]

@johnnyreilly,

Did you have the chance to take a look at the PR?

[johnnyreilly]

Sorry I'm currently snowed @fatme

I will try and take a look but it won't be immediately I'm afraid