TS error in eslint.config.mts "Type 'Config[]' is not assignable to type 'ExtendsElement[]'."

[PBonnema]

Which @ngrx/* package(s) are the source of the bug?

eslint-plugin

Minimal reproduction of the bug/regression with instructions

• Generate a new eslint config file with npx eslint --init.
• Choose TypeScript as the language for the new config file.
• Add the NgRx ESLint plugin to the new eslint.config.mts according to these instructions https://ngrx.io/guide/eslint-plugin#eslint-v9.
• You encounter a typescript error about a type mismatch on the extends part: extends: [...ngrx.configs.all]

Type 'Config[]' is not assignable to type 'ExtendsElement[]'.
  Type 'Config' is not assignable to type 'ExtendsElement'.
    Type 'Config' is not assignable to type 'Config<RulesRecord>'.
      Types of property 'languageOptions' are incompatible.
        Type 'import("d:/repos/Fourth-World/node_modules/@typescript-eslint/utils/dist/ts-eslint/Config").FlatConfig.LanguageOptions | undefined' is not assignable to type 'import("d:/repos/Fourth-World/node_modules/eslint/lib/types/index").Linter.LanguageOptions | undefined'.
          Type 'import("d:/repos/Fourth-World/node_modules/@typescript-eslint/utils/dist/ts-eslint/Config").FlatConfig.LanguageOptions' is not assignable to type 'import("d:/repos/Fourth-World/node_modules/eslint/lib/types/index").Linter.LanguageOptions'.
            Types of property 'parser' are incompatible.
              Type 'LooseParserModule | undefined' is not assignable to type 'Parser | undefined'.
                Type '{ meta?: { name?: string | undefined; version?: string | undefined; } | undefined; parseForESLint(text: string, options?: unknown): { ast: unknown; scopeManager?: unknown; services?: unknown; visitorKeys?: unknown; }; }' is not assignable to type 'Parser | undefined'.
                  Type '{ meta?: { name?: string | undefined; version?: string | undefined; } | undefined; parseForESLint(text: string, options?: unknown): { ast: unknown; scopeManager?: unknown; services?: unknown; visitorKeys?: unknown; }; }' is not assignable to type 'ObjectMetaProperties & { parseForESLint(text: string, options?: any): ESLintParseResult; }'.
                    Type '{ meta?: { name?: string | undefined; version?: string | undefined; } | undefined; parseForESLint(text: string, options?: unknown): { ast: unknown; scopeManager?: unknown; services?: unknown; visitorKeys?: unknown; }; }' is not assignable to type '{ parseForESLint(text: string, options?: any): ESLintParseResult; }'.
                      The types of 'parseForESLint(...).ast' are incompatible between these types.
                        Type 'unknown' is not assignable to type 'Program'.ts(2322)

• Additionally, you get another error in your regular code files:

• The result is that the plugin does not work at all.
• When you use a JS version of eslint.config.mts, then the errors are slightly different because you don't see the type error (it's JS) but the end result is that same as in the plugin being broken.

Expected behavior

I expected the type of ngrx.configs.all to be compatible with the extends field in the object array which is the parameter of defineConfig() in the eslint config file such that the NgRxplugin works again with ES lint.

Versions of NgRx, Angular, Node, affected browser(s) and operating system(s)

> npm ls
<omitted>
  ├── @angular-eslint/builder@20.3.0
  ├── @angular-eslint/eslint-plugin-template@20.3.0
  ├── @angular-eslint/eslint-plugin@20.3.0
  ├── @angular-eslint/schematics@20.3.0
  ├── @angular-eslint/template-parser@20.3.0
  ├── @angular/build@20.3.1
  ├── @angular/cdk@20.2.3
  ├── @angular/cli@20.3.1
  ├── @angular/common@20.3.0
  ├── @angular/compiler-cli@20.3.0
  ├── @angular/compiler@20.3.0
  ├── @angular/core@20.3.0
  ├── @angular/forms@20.3.0
  ├── @angular/material@20.2.3
  ├── @angular/platform-browser@20.3.0
  ├── @angular/router@20.3.0
  ├── @eslint/css@0.11.0
  ├── @eslint/js@9.36.0
  ├── @eslint/json@0.13.2
  ├── @eslint/markdown@7.2.0
  ├── @microsoft/signalr@9.0.6
  ├── @ngrx/effects@20.0.1
  ├── @ngrx/entity@20.0.1
  ├── @ngrx/eslint-plugin@20.0.1
  ├── @ngrx/operators@20.0.1
  ├── @ngrx/router-store@20.0.1
  ├── @ngrx/schematics@20.0.1
  ├── @ngrx/signals@20.0.1
  ├── @ngrx/store-devtools@20.0.1
  ├── @ngrx/store@20.0.1
  ├── @types/jasmine@5.1.9
  ├── @types/node@24.4.0
  ├── eslint@9.36.0
  ├── globals@16.4.0
  ├── jasmine-core@5.9.0
  ├── jiti@2.5.1
  ├── karma-chrome-launcher@3.2.0
  ├── karma-coverage@2.2.1
  ├── karma-jasmine-html-reporter@2.1.0
  ├── karma-jasmine@5.1.0
  ├── karma@6.4.4
  ├── prettier@3.6.2
  ├── rxjs@7.8.2
  ├── tslib@2.8.1
  ├── typescript-eslint@8.44.0
  └── typescript@5.9.2

Node.js v24.8.0
On Windows 11

Other information

No response

I would be willing to submit a PR to fix this issue

• Yes
• No

[jdegand]

@PBonnema Try using a type assertion to get around this:

// eslint.config.mts
import { defineConfig } from 'eslint'
import typescript from '@eslint/js'
import tseslint from 'typescript-eslint'
import * as ngrx from '@ngrx/eslint-plugin/v9'

export default defineConfig([
  ...typescript.configs.recommended,
  ...tseslint.configs.recommended,
  //  Type assertion to fix type mismatch
  ...(ngrx.configs.all as unknown as import('eslint').Linter.Config[]),
])

[jdegand]

Update: There might be a type mismatch with the dependencies. I would try updating the typescript-eslint dependencies:
npm install @typescript-eslint/utils@9 @typescript-eslint/parser@9 @typescript-eslint/eslint-plugin@9

[PBonnema]

@jdegand Those versions don't exist. Version 8.44.0 is the latest

[jdegand]

@PBonnema Yes, you are right. I was looking through the typescript-eslint repo and others and this seems to be a mess converting eslint 8 to 9. The maintainers had to basically disregard typing with unknown to support both versions at once. Looking at some ideas from AI, it recommends using type assertions as any in plugin array and other places.

[PBonnema]

The issue is not just the type mismatch. The issue is that the plugin is fundamentally broken because 'ngrx.configs.all' now seems to be not defineConfig() function needs to do its thing and so the linting rules from the plugin are never loaded. That then breaks the whole of ESlint, leading to the error in my screenshot with no linting suggestions being given anymore.