Fix dependency cycle reporting

loader/src/main/java/net/neoforged/fml/loading/ModSorter.java

@@ -32,7 +32,6 @@
 import net.neoforged.fml.ModLoadingException;
 import net.neoforged.fml.ModLoadingIssue;
 import net.neoforged.fml.loading.moddiscovery.ModFile;
-import net.neoforged.fml.loading.moddiscovery.ModFileInfo;
 import net.neoforged.fml.loading.moddiscovery.ModInfo;
 import net.neoforged.fml.loading.toposort.CyclePresentException;
 import net.neoforged.fml.loading.toposort.TopologicalSort;
@@ -99,7 +98,7 @@ public static LoadingModList sort(List<ModFile> plugins, List<ModFile> gameLibra
             if (modLoadingException == null) {
                 list = LoadingModList.of(plugins, gameLibraries, ms.modFiles, ms.sortedList, issues, ms.modDependencies);
             } else {
-                list = LoadingModList.of(plugins, gameLibraries, ms.modFiles, ms.sortedList, concat(issues, modLoadingException.getIssues()), Map.of());
+                list = LoadingModList.of(plugins, gameLibraries, ms.systemMods, ms.systemMods.stream().map(mf -> (ModInfo) mf.getModInfos().getFirst()).collect(toList()), concat(issues, modLoadingException.getIssues()), Map.of());
             }
         }
 
@@ -171,14 +170,15 @@ private void sort(List<ModLoadingIssue> issues) {
         try {
             sorted = TopologicalSort.topologicalSort(graph, Comparator.comparing(infos::get));
         } catch (CyclePresentException e) {
-            Set<Set<ModFileInfo>> cycles = e.getCycles();
+            Set<Set<ModInfo>> cycles = e.getCycles();
             if (LOGGER.isErrorEnabled(LogMarkers.LOADING)) {
                 LOGGER.error(LogMarkers.LOADING, "Mod Sorting failed.\nDetected Cycles: {}\n", cycles);
             }
             var dataList = cycles.stream()
-                    .<ModFileInfo>mapMulti(Iterable::forEach)
-                    .<IModInfo>mapMulti((mf, c) -> mf.getMods().forEach(c))
-                    .map(IModInfo::getModId)
+                    .map(cycle -> cycle.stream()
+                            .map(IModInfo::getModId)
+                            .sorted()
+                            .collect(Collectors.joining(", ")))
                     .map(list -> ModLoadingIssue.error("fml.modloadingissue.cycle", list).withCause(e))
                     .toList();
             throw new ModLoadingException(dataList);

loader/src/main/java/net/neoforged/fml/loading/moddiscovery/ModInfo.java

@@ -201,6 +201,11 @@ private ForgeFeature.Bound makeBound(Map.Entry<String, Object> e) {
         }
     }
 
+    @Override
+    public String toString() {
+        return modId + " (" + displayName + ") @ " + version;
+    }
+
     class ModVersion implements net.neoforged.neoforgespi.language.IModInfo.ModVersion {
         private IModInfo owner;
         private final String modId;

loader/src/test/java/net/neoforged/fml/loading/FMLLoaderTest.java

@@ -794,6 +794,35 @@ void testMissingRequiredDependency() throws Exception {
             assertThat(getTranslatedIssues(e.getIssues())).containsOnly("ERROR: Mod testmod requires requiredmod any\nCurrently, requiredmod is not installed\n");
         }
 
+        @Test
+        void testDependencyCycle() throws Exception {
+            installation.setupProductionClient();
+            installation.buildModJar("mod_one.jar")
+                    .withModsToml(builder -> {
+                        builder.unlicensedJavaMod();
+                        builder.addMod("mod_one", "1.0");
+                        builder.addDependency("mod_one", "mod_two", "[1.0,)", dep -> dep.set("ordering", "BEFORE"));
+                    })
+                    .build();
+            installation.buildModJar("mod_two.jar")
+                    .withModsToml(builder -> {
+                        builder.unlicensedJavaMod();
+                        builder.addMod("mod_two", "1.0");
+                        builder.addDependency("mod_two", "mod_three", "[1.0,)", dep -> dep.set("ordering", "BEFORE"));
+                    })
+                    .build();
+            installation.buildModJar("mod_three.jar")
+                    .withModsToml(builder -> {
+                        builder.unlicensedJavaMod();
+                        builder.addMod("mod_three", "1.0");
+                        builder.addDependency("mod_three", "mod_one", "[1.0,)", dep -> dep.set("ordering", "BEFORE"));
+                    })
+                    .build();
+
+            var e = assertThrows(ModLoadingException.class, () -> launchInstalledDist());
+            assertThat(getTranslatedIssues(e.getIssues())).containsOnly("ERROR: Detected a mod dependency cycle: mod_one, mod_three, mod_two");
+        }
+
         @Test
         void testDependencyOverride() throws Exception {
             installation.setupProductionClient();