Unable to resolve module error when importing from package with only type definitions

[thw0rted]

I use the NPM package @esri/arcgis-rest-types in a project, and I'm trying to hook up Karma testing using this plugin. It's notable because this package contains no runtime code at all, only .d.ts typings. When my code imports one of the types from this package, I get the message ERROR [karma-server]: Error: Unable to resolve module [@esri/arcgis-rest-types] from {source file path}.

I put together a simple reproduction. Clone and npm install, then npm run build and npm run start -- you should see some simple console output. Note that the emitted code does not include any references to the Esri package, since it only contains type information. Now, run npm run test, and you should see the aforementioned message.

The way I see it, one of three things is happening here:

1. I have my project configured wrong for what I'm trying to do, in which case I'd appreciate any pointers, or
2. The way Esri has packaged these types to distribute via NPM is wrong -- bad package.json or something? -- and for some reason the Typescript language service and Webpack are both happy to use them anyway, while this plugin (correctly) fails, or
3. This is a bug in the plugin , and it can't handle "empty" packages like this one correctly

If it helps, I can try to find other similar packages that export types only, but aren't in the @types namespace and aren't meant to be used in an ambient context.

[07akioni]

@erikbarke Could you please have a look at the issue? Thanks a lot. I've met the same problem.

It can be reproduced in https://github.com/monounity/karma-typescript/tree/master/examples/typescript-latest

Just run npm i csstype and add import { Properties } from 'csstype' at the 2nd line of src/hello.component.ts then the error happens.

23 02 2021 23:28:33.962:ERROR [karma-server]: UncaughtException: Error: Unable to resolve module [csstype] from [/Users/hrsonion/Development/Dev2021/karma-typescript/examples/typescript-latest/src/hello.component.js]

[thw0rted]

Thanks @07akioni for figuring it out and @erikbarke for the merge! Is there an easy way to tell when this shows up on NPM?

[erikbarke]

@thw0rted, @07akioni, v5.5.0 is on npm now 🚀