fix: filter import errors and close #653

[rolandjitsu]

Fix for #653 (following #653 (comment)). Note that I did not add any tests as I was unsure where to add the tests.

[johnnyreilly]

Could you share a minimal repo that demonstrates this issue? I can use that as a basis for an execution test.

Also, can you confirm that you experience this regardless of the value of the emitDecoratorMetadata flag? Thanks!

[rolandjitsu]

Let me setup that 😄

[rolandjitsu]

@johnnyreilly I just setup tsl-import, but I also just found that you can already disable these warnings with:

stats: {
  warningsFilter: /export .* was not found in/
}

But if you switch to react-scripts-ts branch, you can still see the same kind of error, but different message. I'm trying to track it down as I'm not sure if this is coming from ts-loader.

If I change transpileOnly to false in their webpack config, everything compiles just fine.

[johnnyreilly]

But if you switch to react-scripts-ts branch, you can still see the same kind of error, but different message. I'm trying to track it down as I'm not sure if this is coming from ts-loader.

It'll likely be coming from: https://github.com/Realytics/fork-ts-checker-webpack-plugin

react-scripts-ts uses that for checking types and ts-loader for transpilation.

[rolandjitsu]

That's the thing, I'm not so sure about that as I removed the plugin from the webpack config and I still see this error.

For instance, in my example repo, if you checkout the react-scripts-ts-ejected branch and disable the transpile only option, all goes well.

It also seems strange that with transpileOnly: true it does show the error, but with transpileOnly: false it does not. If it were a different tool that is independent from ts-loader, it should always show the error.

[rolandjitsu]

In any case, I don't think this PR will solve the issue anyway, so maybe we should close it?

[johnnyreilly]

That's the thing, I'm not so sure about that as I removed the plugin from the webpack config and I still see this error.

react-scripts-ts is still webpack 3. I wonder if that's the reason?

[johnnyreilly]

In any case, I don't think this PR will solve the issue anyway, so maybe we should close it?

If you're sure. I'm sorry you went to wasted effort though!

[rolandjitsu]

That's the thing, I'm not so sure about that as I removed the plugin from the webpack config and I still see this error.

react-scripts-ts is still webpack 3. I wonder if that's the reason?

I will try with w4 and see how that works out. Actually, the next tag on npm of create-scripts-ts is using webpack 4 (see react-scripts-ts-ejected/package.json#L61).

[rolandjitsu]

Ok, I tracked down the error. Seems to be happening at webpack/lib/dependencies/HarmonyExportImportedSpecifierDependency.js.

[rolandjitsu]

Could I ask what is different from what ts-loader generates as output with transpileOnly: true vs transpileOnly: false?

[johnnyreilly]

Sure - there's a subtle difference in terms of produced code; but this only comes into play rarely; when emitDecoratorMetadata: true is in play and also I've an idea that imported enums also have a nuance. There may be more detail here:

https://github.com/Microsoft/TypeScript/wiki/Using-the-Compiler-API#transpiling-a-single-file