Use module.exports export to detect CJS config

package.json

@@ -250,7 +250,6 @@
     "mkdirp": "^3.0.0",
     "mz": "^2.7.0",
     "progress": "^2.0.3",
-    "read-package-up": "^11.0.0",
     "semver": "7.7.2",
     "string-argv": "0.3.1",
     "supports-color": "^8.1.1",

src/configuration/from_file.ts

@@ -107,24 +107,20 @@ async function loadFile(
       break
     case '.js':
       {
-        const parentPackage = await readPackageJson(filePath)
-        if (!parentPackage) {
+        logger.debug(
+          `Loading configuration file "${file}" as JavaScript based on extension`
+        )
+        const ambiguous = await import(pathToFileURL(filePath).toString())
+        if ('module.exports' in ambiguous) {
           logger.debug(
-            `Loading configuration file "${file}" as CommonJS based on absence of a parent package`
+            `Treating configuration file "${file}" as CommonJS based on heuristics`
           )
-          // eslint-disable-next-line @typescript-eslint/no-require-imports
-          definitions = require(filePath)
-        } else if (parentPackage.type === 'module') {
-          logger.debug(
-            `Loading configuration file "${file}" as ESM based on "${parentPackage.name}" package type`
-          )
-          definitions = await import(pathToFileURL(filePath).toString())
+          definitions = ambiguous['module.exports']
         } else {
           logger.debug(
-            `Loading configuration file "${file}" as CommonJS based on "${parentPackage.name}" package type`
+            `Treating configuration file "${file}" as ESM based on heuristics`
           )
-          // eslint-disable-next-line @typescript-eslint/no-require-imports
-          definitions = require(filePath)
+          definitions = ambiguous
         }
       }
       break
@@ -136,9 +132,3 @@ async function loadFile(
   }
   return definitions
 }
-
-async function readPackageJson(filePath: string) {
-  const { readPackageUp } = await import('read-package-up')
-  const parentPackage = await readPackageUp({ cwd: path.dirname(filePath) })
-  return parentPackage?.packageJson
-}