update config to support default definition function

src/configuration/from_file.ts

@@ -15,8 +15,21 @@ export async function fromFile(
   file: string,
   profiles: string[] = []
 ): Promise<Partial<IConfiguration>> {
-  const definitions = await loadFile(logger, cwd, file)
-  if (!definitions.default) {
+  let definitions = await loadFile(logger, cwd, file)
+
+  const defaultDefinition: unknown = definitions.default
+
+  if (defaultDefinition) {
+    if (typeof defaultDefinition === 'function') {
+      const definitionsFromDefault = await defaultDefinition()
+
+      definitions = {
+        ...definitions,
+        default: {},
+        ...definitionsFromDefault,
+      }
+    }
+  } else {
     logger.debug('No default profile defined in configuration file')
     definitions.default = {}
   }

src/configuration/from_file_spec.ts

@@ -98,6 +98,29 @@ describe('fromFile', () => {
       expect(result).to.deep.eq({ paths: ['other/path/*.feature'] })
     })
 
+    it('should work with .mjs with default function', async () => {
+      const { logger, cwd } = await setup(
+        'cucumber.mjs',
+        `export default async function() { 
+          return {
+            default: { paths: ['default/path/*.feature'] },
+            p1: { paths: ['p1/path/*.feature'] }
+          };
+        };
+        export const p1 = { paths: ['other/p1/path/*.feature'] };
+        export const p2 = { paths: ['p2/path/*.feature'] };`
+      )
+
+      const p1Result = await fromFile(logger, cwd, 'cucumber.mjs', ['p1'])
+      const p2Result = await fromFile(logger, cwd, 'cucumber.mjs', ['p2'])
+      const defaultResult = await fromFile(logger, cwd, 'cucumber.mjs', [
+        'default',
+      ])
+      expect(p1Result).to.deep.eq({ paths: ['p1/path/*.feature'] })
+      expect(p2Result).to.deep.eq({ paths: ['p2/path/*.feature'] })
+      expect(defaultResult).to.deep.eq({ paths: ['default/path/*.feature'] })
+    })
+
     it('should work with .cjs', async () => {
       const { logger, cwd } = await setup(
         'cucumber.cjs',