add ability for mods to provide further mod providers

minecraft/src/main/java/dev/frogmc/frogloader/example/ExampleModProvider.java

@@ -0,0 +1,10 @@
+package dev.frogmc.frogloader.example;
+
+import dev.frogmc.frogloader.api.plugin.ModProvider;
+
+public class ExampleModProvider implements ModProvider {
+	@Override
+	public String id() {
+		return "example_mod:example";
+	}
+}

minecraft/src/main/resources/frog.mod.toml

@@ -14,4 +14,4 @@ credits = [
 prelaunch = "dev.frogmc.frogloader.example.ExamplePreLaunchExtension"
 mixin = "example_mod.mixins.json"
 accesswidener = "example_mod.accesswidener"
-
+modprovider = "dev.frogmc.frogloader.example.ExampleModProvider"

src/main/java/dev/frogmc/frogloader/impl/PluginLoader.java

@@ -1,11 +1,8 @@
 package dev.frogmc.frogloader.impl;
 
 import java.nio.file.Path;
-import java.util.Collection;
+import java.util.*;
-import java.util.HashMap;
+import java.util.concurrent.atomic.AtomicInteger;
-import java.util.Map;
-import java.util.ServiceLoader;
-import java.util.stream.Collectors;
 
 import dev.frogmc.frogloader.api.FrogLoader;
 import dev.frogmc.frogloader.api.mod.ModProperties;
@@ -26,37 +23,50 @@ public class PluginLoader {
 	public static void discoverModProviders(Path gameDir, Map<String, Map<String, ModProperties>> mods, Collection<String> modIds, Collection<ModProvider> modProviders) throws ModDependencyResolver.ResolverException {
 		LOGGER.info("Discovering mod providers...");
 
-		for (ModProvider plugin : ServiceLoader.load(ModProvider.class)) {
+		List<ModProvider> providers = new ArrayList<>(ServiceLoader.load(ModProvider.class).stream().map(ServiceLoader.Provider::get).toList()); // we need mutability & random access
+		Map<String, Collection<ModProperties>> properties = new HashMap<>();
+		AtomicInteger size = new AtomicInteger(providers.size()); // use a separate size variable to not have to iterate over the list over and over again
+		for (int i = 0; i < size.get(); i++) {
+			ModProvider plugin = providers.get(i); // use random access to work around concurrent access (through modifications during iteration)
 			LOGGER.debug("Found mod provider: {}", plugin.getClass().getName());
 			if (!plugin.isApplicable()) {
 				continue;
 			}
 			try {
 				LOGGER.debug("Initialising mod provider: {}", plugin.id());
-				Map<String, ModProperties> modsFromProvider = new HashMap<>();
+				Collection<ModProperties> loadedMods = plugin.loadMods(Discovery.find(gameDir.resolve(plugin.loadDirectory()),
-				Collection<ModProperties> loadedMods = plugin.loadMods(Discovery.find(gameDir.resolve(plugin.loadDirectory()), plugin::isDirectoryApplicable, plugin::isFileApplicable), FrogLoaderImpl.getInstance().getClassloader()::addURL);
+								plugin::isDirectoryApplicable,
+								plugin::isFileApplicable),
+						FrogLoaderImpl.getInstance().getClassloader()::addURL);
 				initializeModMixins(loadedMods);
 				AWProcessor.load(loadedMods);
 
-				loadedMods.forEach(m -> modsFromProvider.put(m.id(), m));
+				properties.put(plugin.id(), loadedMods);
 
-				LOGGER.debug("Loaded {} mod(s) from provider: {}", modsFromProvider.size(), plugin.id());
+				LOGGER.debug("Loaded {} mod(s) from provider: {}", loadedMods.size(), plugin.id());
-				mods.put(plugin.id(), modsFromProvider);
+				loadedMods.forEach(p -> p.extensions().runIfPresent(BuiltinExtensions.MOD_PROVIDER, ModProvider.class, provider -> {
-				modIds.addAll(modsFromProvider.keySet());
+					providers.add(provider);
-				modProviders.add(plugin);
+					size.getAndIncrement();
+				}));
 			} catch (Throwable e) {
 				LOGGER.error("Error during plugin initialisation: ", e);
 			}
 		}
 
-		Collection<ModProperties> properties = mods.values().stream().map(Map::values).flatMap(Collection::stream).collect(Collectors.toUnmodifiableSet());
+		Collection<ModProperties> flattened = properties.values().stream().flatMap(Collection::stream).toList();
 		try {
-			Collection<ModProperties> solved = new  ModDependencyResolver(properties).solve();
+			Collection<ModProperties> solved = new  ModDependencyResolver(flattened).solve();
-			mods.forEach((s, map) -> map.values().retainAll(solved));
+			properties.forEach((s, c) -> c.retainAll(solved));
+			properties.forEach((s, c) -> {
+				Map<String, ModProperties> map = mods.computeIfAbsent(s, u -> new HashMap<>());
+				c.forEach(p -> map.put(p.id(), p));
+			});
+			modIds.addAll(solved.stream().map(ModProperties::id).toList());
+			modProviders.addAll(providers);
 		} catch (ModDependencyResolver.UnfulfilledDependencyException e) {
-			LoaderGui.execUnfulfilledDep(CrashReportGenerator.writeReport(e, properties), e, false);
+			LoaderGui.execUnfulfilledDep(CrashReportGenerator.writeReport(e, flattened), e, false);
 		} catch (ModDependencyResolver.BreakingModException e) {
-			LoaderGui.execBreakingDep(CrashReportGenerator.writeReport(e, properties), e, false);
+			LoaderGui.execBreakingDep(CrashReportGenerator.writeReport(e, flattened), e, false);
 		}
 	}
 

src/main/java/dev/frogmc/frogloader/impl/mod/BuiltinExtensions.java

@@ -9,4 +9,5 @@ public class BuiltinExtensions {
 	public final String PRE_LAUNCH = "prelaunch";
 	public final String ACCESSWIDENER = "accesswidener";
 	public final String LOADING_TYPE = "loading_type";
+	public final String MOD_PROVIDER = "modprovider";
 }