Eslint 9 compatibility

[lwasyl]

Issue workflow progress

Progress of the issue based on the Contributor Workflow

• [ ] 1. The issue provides a reproduction available on GitHub, Stackblitz or CodeSandbox

  For example, you can start off by editng the 'basic' example on Stackblitz.

  Please make sure the graphql-eslint version under package.json matches yours.

• [ ] 2. A failing test has been provided

• [ ] 3. A local solution has been provided

• [ ] 4. A pull request is pending review

---

Describe the bug

There's an open issue to support eslint 9 flat config files: https://github.com/dimaMachina/graphql-eslint/issues/2178. However, even when opting out from flat config via export ESLINT_USE_FLAT_CONFIG=false, graphql-eslint fails with Eslint 9 due to:

TypeError: Error while loading rule '@graphql-eslint/no-unreachable-types': Cannot destructure property 'schema' of 'context.parserServices' as it is undefined.. Iiuc the problem is that several methods have been deprecated and removed in eslint 9, including context.parserServices which graphql-eslint seems to be calling. Thus it's not only not possible to use flat config, but eslint 9 at all

To Reproduce Steps to reproduce the behavior:

Update eslint to version 9

Expected behavior

graphql-eslint still works

Environment:

• OS: /
• @graphql-eslint/eslint-plugin: 3.20.1
• Node.js: 20.13.1

Additional context

[ldiqual]

Workaround using the compat package from eslint:

import { fixupPluginRules } from '@eslint/compat'
export default [
  {
    plugins: {
      '@graphql-eslint': fixupPluginRules(graphqlPlugin),
    },
    // ...
  }
]