flow types fail compilation in monorepo with CRA next.66cc7a90

Is this a bug report?

yes.

It’s a project with flow annotations. Lines like these appear to trigger the issue:

import type { Props, ComponentState } from './MyComponent.type'

The error is:

Failed to compile.

./src/components/MyComponent.js
Module build failed: TypeError: Cannot read property 'type' of undefined
    at Array.forEach (<anonymous>)
    at Array.forEach (<anonymous>)

Moving the code outside the monorepo and yarn; yarn start: works. Keep it inside and remove all flow annotations: works.

Did you try recovering your dependencies?

Yes. In fact, adding a package.json declaration of

"nohoist": [
  "**/react-scripts", "**/react-scripts/**"
]

works around the issue.

Which terms did you search for in User Guide?

flow, monorepo, workspaces

Environment

Environment:
  OS:  macOS High Sierra 10.13.4
  Node:  8.9.1
  Yarn:  1.6.0
  npm:  6.0.1
  Watchman:  4.9.0
  Xcode:  Xcode 9.3.1 Build version 9E501
  Android Studio:  Not Found

Packages: (wanted => installed)

(paste the output of the command here)

Steps to Reproduce

1. Create a CRA project from scratch
2. Add flow annotations as above
3. yarn; yarn start
4. See it working
5. Move the code into an existing monorepo with yarn workspaces enabled
6. yarn; yarn start
7. See it failing

Expected Behavior

Should just work.

Actual Behavior

Compilation failure per above error.

[bugzpodder]

The reason is that create-react-app won’t process libraries from using non-standard features such as flow and other js features and proposals that are not currently finalized, in order to avoid defragmentation of the js landscape. What you are doing however is just sharing source code between different apps, so its a different use case that create-react-app isn’t supporting right now but will in the future.

[stale[bot]]

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