Argument --allowUnusedTypes does not apply to type re-exports

[kachkaev]

First things first: fantastic tool 😍 I tried it in a large project yesterday and found so much dead code!

I’d like to report one little issue that I’ve noticed. When I add --allowUnusedTypes, I still get reports for types that have been re-exported via export type { Foo } from "./foo";. Here is an MWE:

1. Init the project:

   mkdir ts-unused-exports-false-positives
   cd ts-unused-exports-false-positives
   yarn init --yes
   yarn add -D typescript@4.1.2 ts-unused-exports@7.0.0

   cat <<EOF >tsconfig.json
   {}
   EOF

2. Create TypeScript files

   cat <<EOF >index.ts
   import { fn1 } from "./fn1";
   import { fn2 } from "./fn2";
   
   console.log(fn1({ x: 1, y: 2 }), fn2({ a: 3, b: 4 }));
   EOF

   cat <<EOF >fn1.ts
   export interface Fn1Input {
     x: number;
     y: number;
   }
   
   export const fn1 = (input: Fn1Input): number => input.x + input.y;
   EOF

   cat <<EOF >fn2/fn2.ts
   export interface Fn2Input {
     a: number;
     b: number;
   }
   
   export const fn2 = (input: Fn2Input): number => input.a - input.b;
   EOF

   cat <<EOF >fn2/index.ts
   export { fn2 } from "./fn2";
   export type { Fn2Input } from "./fn2"; // 👈 👀
   EOF

3. Run ts-unused-exports without --allowUnusedTypes

   yarn ts-unused-exports tsconfig.json

   Output:

   2 modules with unused exports
   /path/to/ts-unused-exports-false-positives/fn1.ts: Fn1Input
   /path/to/ts-unused-exports-false-positives/fn2/index.ts: Fn2Input
   error Command failed with exit code 1.

   All works as expected.

4. Run ts-unused-exports with --allowUnusedTypes

   yarn ts-unused-exports tsconfig.json --allowUnusedTypes

   Output:

   1 module with unused exports
   /path/to/ts-unused-exports-false-positives/fn2/index.ts: Fn2Input
   error Command failed with exit code 1.

   Expected output:

   0 modules with unused exports

In the real scenario, I have functions with React components and interfaces with component props. Re-exports are needed because some components are complex and are therefore put into sub-folders. Having export type as an extra line is necessary when the component itself is a default export (it’s not possible to export * from "./fn2" in this case).

Happy to help with finding a solution, if needed. Thanks again for the tool 🙌

[mrseanryan]

Hi @kachkaev thanks for reporting.

I think this could be solved via https://github.com/pzavolinsky/ts-unused-exports/issues/30

[mrseanryan]

TODO:

• add unit or itests to capture the above

• try implementing #30 if that fixes this issue I suggest this because it is a general solution (and making it optional behaviour avoids breaking change).

@kachkaev if you have the time, it would be great to have your contribution!

[kachkaev]

Hi @mrseanryan! I think that the proposed ignoreLocallyUsed option in #30 is not doing quite the same thing. To me, reporting export const a which could be const a is a valid feedback, while --allowUnusedTypes + export type ... is a false positive.

I’m not familiar with the architecture of ts-unused-exports at this point, so I wonder if detecting symbols that stick out via export type is at all feasible. From my observations, --allowUnusedTypes works well already and the only false positives are when there is export type { X } from "./someFile".

Happy to try contributing with the unit tests.

[kachkaev]

I added some broken tests in #181

UPD: Oh wow looks like I fixed it. Neat codebase folks 👍

[mrseanryan]

Thank you @kachkaev for contributing 👍

[mrseanryan]

@pzavolinsky we can release this as a patch :)