Properly propagate exception to sentinel mod (close #2)

src/main/java/org/teacon/sync/SyncedModLocator.java

@@ -21,6 +21,7 @@
 package org.teacon.sync;
 
 import com.google.gson.Gson;
+import com.google.gson.JsonParseException;
 import cpw.mods.modlauncher.Launcher;
 import cpw.mods.modlauncher.api.IEnvironment;
 import net.minecraftforge.fml.loading.moddiscovery.AbstractJarFileLocator;
@@ -46,6 +47,7 @@
 import java.util.Collection;
 import java.util.Map;
 import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.CompletionException;
 import java.util.function.Consumer;
 import java.util.stream.Stream;
 
@@ -86,15 +88,15 @@ public SyncedModLocator() throws Exception {
                 LOGGER.warn("Failed to download mod list", e);
                 throw new RuntimeException(e);
             }
-        }).handleAsync((fcModList, exc) -> {
-            if (exc != null) {
-                return new ModEntry[0];
-            }
+        }).thenApplyAsync((fcModList) -> {
             try (Reader reader = Channels.newReader(fcModList, "UTF-8")) {
                 return GSON.fromJson(reader, ModEntry[].class);
+            } catch (JsonParseException e) {
+                LOGGER.warn("Error parsing modlist", e);
+                throw e;
             } catch (IOException e) {
                 LOGGER.warn("Failed to fetch mod list from remote", e);
-                return new ModEntry[0];
+                throw new RuntimeException(e);
             }
         }).thenComposeAsync(entries -> {
             var futures = Arrays.stream(entries).flatMap(e -> Stream.of(
@@ -130,7 +132,7 @@ public Stream<Path> scanCandidates() {
             return this.fetchPathsTask.join().stream();
         } catch (Exception e) {
             LOGGER.error("Mod downloading worker encountered error and cannot continue. " +
-                    "No mod will be loaded from the remote-synced locator. ", e);
+                    "No mod will be loaded from the remote-synced locator. ", e instanceof CompletionException ? e.getCause() : e);
             System.setProperty("org.teacon.sync.failed", "true");
             return Stream.empty();
         }