example-typescript-eslint-bug

This repo demonstrates two bugs with typescript-eslint using EXPERIMENTAL_useProjectService.

1. extends is not used in the default project's tsconfig.json.
2. parserOptions.extraFileExtensions is not working as expected to setup tsserver for type checking using project references.

pnpm is required to test the patch in this repo which contains a (non-rigorous) fix to resolve both issues.

Expected Errors With Patch

Using the patch, these errors are expected and correctly reported.

pnpm i
pnpm eslint .

# <REDACTED>/packages/package-a/src/test-component.vue
#   8:7   error  Unsafe assignment of an `any` value       @typescript-eslint/no-unsafe-assignment
#   8:34  error  Unexpected any. Specify a different type  @typescript-eslint/no-explicit-any
#
# <REDACTED>/packages/package-a/src/test.ts
#   7:14  error  Unsafe assignment of an `any` value       @typescript-eslint/no-unsafe-assignment
#   7:41  error  Unexpected any. Specify a different type  @typescript-eslint/no-explicit-any

Errors Without Patch

These errors are not expected using typescript-eslint as is and reveals the extends in tsconfig.json is not followed.

# remove from root package.json
#
#    "patchedDependencies": {
#      "@typescript-eslint/typescript-estree@7.11.0": "patches/@typescript-eslint__typescript-estree@7.11.0.patch"
#    },

pnpm i
pnpm eslint .

# <REDACTED>/packages/package-a/src/test-component.vue
#   0:0  error  Parsing error: Cannot read properties of undefined (reading 'target')
# 
# <REDACTED>/packages/package-a/src/test.ts
#   0:0  error  Parsing error: Cannot read properties of undefined (reading 'target')

Errors Without Patch With Workaround

This attempts to work around the issue by using a project-level tsconfig.eslint.json that does not extend.

It reveals a new issue on line 4 where test-component.vue is not associated with packages/package-a/src/tsconfig.src.json by following the project references which is expected to work with extraFileExtensions.

# remove from root package.json (if not already done)
#
#    "patchedDependencies": {
#      "@typescript-eslint/typescript-estree@7.11.0": "patches/@typescript-eslint__typescript-estree@7.11.0.patch"
#    },

pnpm eslint -c eslint.config2.js .

# <REDACTED>/packages/package-a/src/test-component.vue
#   4:7   error  Unsafe assignment of an `any` value       @typescript-eslint/no-unsafe-assignment
#   8:7   error  Unsafe assignment of an `any` value       @typescript-eslint/no-unsafe-assignment
#   8:34  error  Unexpected any. Specify a different type  @typescript-eslint/no-explicit-any
# 
# <REDACTED>/packages/package-a/src/test.ts
#   7:14  error  Unsafe assignment of an `any` value       @typescript-eslint/no-unsafe-assignment
#   7:41  error  Unexpected any. Specify a different type  @typescript-eslint/no-explicit-any