Fix

Author: emmercm

src/modules/dats/datCombiner.ts

@@ -21,11 +21,17 @@ export default class DATCombiner extends Module {
   combine(dats: DAT[]): DAT {
     this.prefixedLogger.trace(`combining ${dats.length} DAT${dats.length === 1 ? '' : 's'}`);
 
+    const games = dats
+      .flatMap((dat) => dat.getGames())
+      .filter(ArrayUtil.filterUniqueMapped((game) => game.hashCode()));
+
+    // Preserve MAME provenance so that consumers relying on {@link DAT.isMame} (e.g. raw archive
+    // checksumming decisions) continue to treat the combined DAT as MAME-derived
+    const isMame = dats.some((dat) => dat.isMame());
+
     const newDat = new LogiqxDAT({
       header: DATCombiner.generateHeader(dats),
-      games: dats
-        .flatMap((dat) => dat.getGames())
-        .filter(ArrayUtil.filterUniqueMapped((game) => game.hashCode())),
+      ...(isMame ? { machine: games } : { games }),
     });
 
     this.prefixedLogger.trace(`done combining ${dats.length} DAT${dats.length === 1 ? '' : 's'}`);

test/modules/dats/datCombiner.test.ts

@@ -2,6 +2,7 @@ import type DAT from '../../../src/models/dats/dat.js';
 import Game from '../../../src/models/dats/game.js';
 import Header from '../../../src/models/dats/logiqx/header.js';
 import LogiqxDAT from '../../../src/models/dats/logiqx/logiqxDat.js';
+import MameDAT from '../../../src/models/dats/mame/mameDat.js';
 import DATCombiner from '../../../src/modules/dats/datCombiner.js';
 import ProgressBarFake from '../../console/progressBarFake.js';
 
@@ -41,3 +42,31 @@ test.each([[1], [10], [100]])('should combine with any number of DATs: %s', (dat
       .toSorted(),
   ).toEqual([...expectedGameNames].toSorted());
 });
+
+test('should not be MAME when no source DAT is MAME', () => {
+  const dats = generateDummyDats(3);
+  const combinedDat = new DATCombiner(new ProgressBarFake()).combine(dats);
+
+  expect(combinedDat.isMame()).toEqual(false);
+});
+
+test('should be MAME when any source DAT is MAME', () => {
+  const dats: DAT[] = [
+    new LogiqxDAT({
+      header: new Header({ name: 'Logiqx' }),
+      games: [new Game({ name: 'Logiqx Game' })],
+    }),
+    new MameDAT({
+      machine: [new Game({ name: 'MAME Machine' })],
+    }),
+  ];
+  const combinedDat = new DATCombiner(new ProgressBarFake()).combine(dats);
+
+  expect(combinedDat.isMame()).toEqual(true);
+  expect(
+    combinedDat
+      .getGames()
+      .map((game) => game.getName())
+      .toSorted(),
+  ).toEqual(['Logiqx Game', 'MAME Machine']);
+});