fix: set processor for flat config, prefer context.languageOptions.parserOptions

.changeset/new-pumpkins-remain.md

@@ -0,0 +1,5 @@
+---
+"eslint-plugin-mdx": patch
+---
+
+fix: set `processor` for flat config

.changeset/purple-terms-agree.md

@@ -0,0 +1,5 @@
+---
+"eslint-plugin-mdx": patch
+---
+
+fix: prefer `context.languageOptions.parserOptions` over `context.parserOptions`

packages/eslint-plugin-mdx/src/configs/flat.ts

@@ -2,15 +2,14 @@ import type { Linter } from 'eslint'
 import * as eslintMdx from 'eslint-mdx'
 
 import * as mdx from '../index.js'
+import { remark } from '../processors/remark.js'
 
 import { codeBlocks } from './code-blocks.js'
 
 // eslint-disable-next-line sonarjs/deprecation
 export const flat: Linter.FlatConfig = {
  files: ['**/*.{md,mdx}'],
  languageOptions: {
- sourceType: 'module',
- ecmaVersion: 'latest',
  parser: eslintMdx,
  globals: {
  React: false,
@@ -19,6 +18,7 @@ export const flat: Linter.FlatConfig = {
  plugins: {
  mdx,
  },
+ processor: remark,
  rules: {
  'mdx/remark': 'warn',
  'no-unused-expressions': 'error',

packages/eslint-plugin-mdx/src/rules/remark.ts

@@ -28,14 +28,17 @@ export const remark: Rule.RuleModule = {
  // eslint-disable-next-line sonarjs/deprecation -- FIXME: ESLint 8.40+ required
  const sourceCode = context.getSourceCode()
 
+ /* istanbul ignore next */
  const {
  extensions,
  markdownExtensions,
  ignoreRemarkConfig,
  remarkConfigPath,
- } =
+ } = {
  // eslint-disable-next-line sonarjs/deprecation -- FIXME: ESLint 8.40+ required
- context.parserOptions as ParserOptions
+ ...context.parserOptions,
+ ...context.languageOptions?.parserOptions,
+ } as ParserOptions
 
  const isMdx = [...DEFAULT_EXTENSIONS, ...(extensions || [])].includes(
  extname,