[Fix] adjust "is source type module" checks for flat config

Also see jest-community/eslint-plugin-jest#1639

CHANGELOG.md

@@ -15,6 +15,7 @@ This change log adheres to standards from [Keep a CHANGELOG](https://keepachange
 - [`export`]: False positive for exported overloaded functions in TS ([#3065], thanks [@liuxingbaoyu])
 - `exportMap`: export map cache is tainted by unreliable parse results ([#3062], thanks [@michaelfaith])
 - `exportMap`: improve cacheKey when using flat config ([#3072], thanks [@michaelfaith])
+- adjust "is source type module" checks for flat config ([#2996], thanks [@G-Rath])
 
 ### Changed
 - [Docs] [`no-relative-packages`]: fix typo ([#3066], thanks [@joshuaobrien])
@@ -1165,6 +1166,7 @@ for info on changes for earlier releases.
 [#3011]: https://github.com/import-js/eslint-plugin-import/pull/3011
 [#3004]: https://github.com/import-js/eslint-plugin-import/pull/3004
 [#2998]: https://github.com/import-js/eslint-plugin-import/pull/2998
+[#2996]: https://github.com/import-js/eslint-plugin-import/pull/2996
 [#2993]: https://github.com/import-js/eslint-plugin-import/pull/2993
 [#2991]: https://github.com/import-js/eslint-plugin-import/pull/2991
 [#2989]: https://github.com/import-js/eslint-plugin-import/pull/2989

src/core/sourceType.js

@@ -1,7 +1,12 @@
 /**
  * @param {import('eslint').Rule.RuleContext} context
- * @returns 'module' | 'script' | undefined
+ * @returns 'module' | 'script' | 'commonjs' | undefined
  */
 export default function sourceType(context) {
-  return context.parserOptions.sourceType;
+  if ('sourceType' in context.parserOptions) {
+    return context.parserOptions.sourceType;
+  }
+  if ('languageOptions' in context && context.languageOptions) {
+    return context.languageOptions.sourceType;
+  }
 }