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[TS] Const enums in third party packages

See original GitHub issue

I’m having problems using Typescript with the dependencies that use Const enums. I’m getting the folowing error: Type error: Ambient const enums are not allowed when the '--isolatedModules' flag is provided.

I wanted to disable the flag but it seems CRA is forcing it. Is there a workaround around this?

Issue Analytics

State:
Created 5 years ago
Reactions:2
Comments:9 (2 by maintainers)

Top GitHub Comments

2reactions

ianschmitzcommented, Nov 9, 2018

Have you tried turning off skipLibCheck? I’m using Monaco in an app as well (0.12 I think so a few months old)

1reaction

alangpiercecommented, Dec 2, 2018

@alangpierce could you describe how you set it up?

It really depends on the build system, but I think in most situations setting isolatedModules to false should just work.

Some examples that I just tried:

Create React App is the most difficult since the start script edits your tsconfig.json file to set isolatedModules to true. I was able to get it working by ejecting, setting isolatedModules to false in tsconfig.json, and removing the isolatedModules: true line in the ForkTsCheckerWebpackPlugin constructor in config/webpack.config.dev.js and config/webpack.config.prod.js. As far as I know there isn’t a way to get it working without ejecting.
With ts-loader, I’m pretty sure you can set transpileOnly: true or happyPackMode: true and it will work just fine even when isolatedModules is false in your tsconfig.
With ts-node, you can use ts-node/register/transpile-only just fine even when isolatedModules is false in the tsconfig.
With gulp-typescript, I was able to get it to work by setting isolatedModules: false in my tsconfig.json and by passing in isolatedModules: true when calling createProject. This switches it to use per-file compilation, and you don’t get any isolatedModules errors because it disables typechecking.

In every one of these cases, setting isolatedModules: false is scary because it disables real safety checks that TypeScript would report. Setting it to false is a workaround to stop third-party libraries from breaking your build by including const enums, but it means that you need to be careful to not use TS features that need cross-file information to be transpiled (const enums, namespaces, re-exported types).

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