Typescript file in __tests__ with incorrect extension causes unrelated errors to be ignored in yarn build

[mungojam]

Describe the bug

We're in the middle of a conversion to typescript and found that noImplicitAny errors weren't getting reported in react-scripts build which was incorrectly succeeding.

I've now isolated the cause which is a very odd one based on the presence of any typescript files with incorrect extensions in __tests__ directories. To be clear, the errors that should be getting reported are in regular react files/directories, not the __tests__ folder (i.e. this isn't the same as #5626).

So if there is a file containing jsx with the incorrect extension ts instead of tsx, and it is in a __tests__ folder, then all noImplicitAny errors get blotted out wherever they are and react-scripts build succeeds.

VS Code reports the errors throughout.

Did you try recovering your dependencies?

Yes

yarn --version:

2.0.0-rc.35

Which terms did you search for in User Guide?

typescript, noImplicitAny

Environment

Environment Info:

current version of create-react-app: 3.4.1
running from C:\Users\me\AppData\Local\Yarn\Data\global\node_modules\create-react-app

System:
OS: Windows 10 10.0.17134
CPU: (4) x64 Intel(R) Core(TM) i7-6500U CPU @ 2.50GHz
Binaries:
Node: 12.14.1 - C:\Program Files\nodejs\node.EXE
Yarn: 2.0.0-rc.35 - C:\Program Files (x86)\Yarn\bin\yarn.CMD
npm: 6.13.4 - C:\Program Files\nodejs\npm.CMD
Browsers:
Edge: 42.17134.1098.0
Internet Explorer: 11.0.17134.1
npmPackages:
react: Not Found
react-dom: Not Found
react-scripts: Not Found
npmGlobalPackages:
create-react-app: Not Found

Steps to reproduce

1. Standard create-react-app with typescript
2. In the App.tsx add a function with a parameter without a type (e.g. const someFunc = a => a) and use it in the app component.
3. yarn build and you will see the correct noImplicitAny error.
4. Add a file with a .ts (not .tsx) extension to the __tests__ folder. Make the file a valid tsx file by importing react and adding some jsx like const a = <div />
5. yarn build, which will now succeed without errors or warnings even though our App.jsx still has a clear typescript error in it.
6. Move the .ts file out of the tests folder into a regular folder and yarn build then correctly gives an error due to the wrong file extension.
   or
   6b. Rename the .ts file to have a .tsx extension and then yarn build gives the correct error as in step 3.

See my reproducible example on GitHub below.

Expected behavior

It should either give the typescript parse error due to incorrect extension which shows when moving the file out of __tests__, or it should give the noImplicitAny error that shows when correcting the file extension to tsx but leaving in __tests__.

Ideally the first, but that may not be possible yet due to #5626.

Actual behavior

yarn build reports no errors and builds successfully despite there being a clear typescript error in the index.tsx file. The error is correctly reported if the __tests__ folder is deleted or if the file in it is renamed to have the correct .tsx extension.

Reproducible demo

https://github.com/mungojam/MRE-Typescript-Non-Error

1. clone the repo
2. yarn install (we use yarn 2, but you can presumably make it work with yarn 1)
3. yarn build

The build succeeds, when it should fail.

Then to make it correctly fail, either switch to either of the other branches, or manually:

1. Correct the src/__tests__/a.ts file extension to tsx
2. yarn build which then gives the correct error about noImplicitAny in index.tsx.

Or

1. Move the src/__tests__/a.ts file extension to the src folder.
2. yarn build which then gives the correct error about the file not being parsable, because it has jsx in it with the wrong file extension.

[stale]

This issue has been automatically marked as stale because it has not had any recent activity. It will be closed in 5 days if no further activity occurs.

[mungojam]

Please leave open and fix, it's a big gotcha that let linting issues get to production in our case

[stale]

This issue has been automatically marked as stale because it has not had any recent activity. It will be closed in 5 days if no further activity occurs.

[mungojam]

Feels like a major issue to us

[stale]

This issue has been automatically marked as stale because it has not had any recent activity. It will be closed in 5 days if no further activity occurs.

[mungojam]

let's just hope we don't allow errors through to production because of this

[stale]

This issue has been automatically marked as stale because it has not had any recent activity. It will be closed in 5 days if no further activity occurs.

[iansu]

TypeScript does not support JSX inside of a .ts file, only .tsx files.

[mungojam]

But that shouldn't lead to real, unrelated errors in other files going undetected

…

On Wed, 19 May 2021, 18:58 Ian Sutherland, ***@***.***> wrote: Closed #9160 <#9160>. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#9160 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAYCFS6MM5DGJMPI5VN6NXLTOP33JANCNFSM4N6MPFTQ> .