eslint-config-react-app > @typescript-eslint/parser missing typescript?

Describe the bug

Running: npx eslint . Returns: Failed to load parser '@typescript-eslint/parser' declared in 'package.json » eslint-config-react-app#overrides[0]': Cannot find module 'typescript'

Did you try recovering your dependencies?

Tried reinstalling everything, sadly it didn’t work.

I’ve also tried installing typescript as described in the error but it was lacking a tsconfig.json and I also doubt I should have one if this is not a typescript project.

Environment

Environment Info:

  current version of create-react-app: 3.4.0
  running from /Users/peteyycz/.nvm/versions/node/v10.19.0/lib/node_modules/create-react-app

  System:
    OS: macOS 10.15.4
    CPU: (4) x64 Intel(R) Core(TM) i5-5257U CPU @ 2.70GHz
  Binaries:
    Node: 10.19.0 - ~/.nvm/versions/node/v10.19.0/bin/node
    Yarn: Not Found
    npm: 6.14.2 - ~/.nvm/versions/node/v10.19.0/bin/npm
  Browsers:
    Chrome: 80.0.3987.149
    Firefox: 74.0
    Safari: 13.1
  npmPackages:
    react: ^16.13.1 => 16.13.1
    react-dom: ^16.13.1 => 16.13.1
    react-scripts: 3.4.1 => 3.4.1
  npmGlobalPackages:
    create-react-app: 3.4.0

Steps to reproduce

(Write your steps here:)

1. npx create-react-app myapp
2. cd myapp
3. npx eslint .

Expected behavior

It should have ran eslint.

Actual behavior

Failed to load parser '@typescript-eslint/parser' declared in 'package.json » eslint-config-react-app#overrides[0]': Cannot find module 'typescript'

Additional resources

Based on my investigation it might be related to how eslint is now resolving configuration:

https://eslint.org/docs/user-guide/migrating-to-6.0.0#package-loading-simplification Which I have found here: https://github.com/standard/semistandard/issues/249

EDIT: although now I think about it it’s probably a different issue: their case the plugin was missing but in my case the plugin is found but the plugin is missing typescript as a peerdep.

---

https://github.com/facebook/create-react-app/blob/master/packages/eslint-config-react-app/package.json#L19

and this optional: https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/parser/package.json#L56 is not really optional

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Might also be related https://github.com/eslint/eslint/issues/12376

[alex-benoit]

you can fix this by adding typescript to your dependencies

npm install typescript --save-dev

[tnovau]

yarn add -D typescript