Add FeatureFlag API

paper-server/src/test/java/io/papermc/paper/world/flag/FeatureFlagTest.java

@@ -0,0 +1,99 @@
+package io.papermc.paper.world.flag;
+
+import io.papermc.paper.adventure.PaperAdventure;
+import io.papermc.paper.registry.PaperRegistries;
+import io.papermc.paper.registry.RegistryAccess;
+import io.papermc.paper.registry.RegistryKey;
+import io.papermc.paper.registry.entry.RegistryEntry;
+import java.util.HashSet;
+import java.util.Set;
+import java.util.stream.Stream;
+import net.kyori.adventure.key.Key;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.resources.ResourceLocation;
+import net.minecraft.world.flag.FeatureElement;
+import net.minecraft.world.flag.FeatureFlagSet;
+import net.minecraft.world.flag.FeatureFlags;
+import org.bukkit.FeatureFlag;
+import org.bukkit.Keyed;
+import org.bukkit.support.RegistryHelper;
+import org.bukkit.support.environment.AllFeatures;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.MethodSource;
+
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertInstanceOf;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.fail;
+
+@AllFeatures
+class FeatureFlagTest {
+
+    @Test
+    void testFeatureFlagParity() {
+        final Set<ResourceLocation> locations = new HashSet<>();
+        for (final FeatureFlag flag : FeatureFlag.ALL_FLAGS.values()) {
+            locations.add(PaperAdventure.asVanilla(flag.getKey()));
+        }
+        FeatureFlags.REGISTRY.fromNames(locations, unknown -> {
+            fail("Unknown api feature flag: " + unknown);
+        });
+
+        for (final ResourceLocation nmsFlag : allNames()) {
+            assertNotNull(FeatureFlag.ALL_FLAGS.value(Key.key(nmsFlag.toString())), "can't find api flag for " + nmsFlag);
+        }
+    }
+
+    @Test
+    void testFeatureFlagConversion() {
+        assertEquals(allNames().size(), PaperFeatureFlagProviderImpl.FLAGS.size());
+        for (final FeatureFlag featureFlag : PaperFeatureFlagProviderImpl.FLAGS.keySet()) {
+            final net.minecraft.world.flag.FeatureFlag nmsFlag = PaperFeatureFlagProviderImpl.FLAGS.get(featureFlag);
+            final ResourceLocation nmsFlagName = FeatureFlags.REGISTRY.toNames(FeatureFlagSet.of(nmsFlag)).iterator().next();
+            assertEquals(nmsFlagName.toString(), featureFlag.key().asString());
+        }
+    }
+
+    static Set<ResourceLocation> allNames() {
+        return FeatureFlags.REGISTRY.toNames(FeatureFlags.REGISTRY.allFlags());
+    }
+
+    @SuppressWarnings({"rawtypes", "unchecked"})
+    static Set<RegistryKey<?>> featureFilteredRegistries() {
+        final Set<RegistryKey<?>> registryKeys = new HashSet<>();
+        for (final ResourceKey filteredRegistry : FeatureElement.FILTERED_REGISTRIES) {
+            registryKeys.add(PaperRegistries.registryFromNms(filteredRegistry));
+        }
+        return registryKeys;
+    }
+
+    @MethodSource("featureFilteredRegistries")
+    @ParameterizedTest
+    <T extends Keyed> void testApiImplementsFeatureDependant(final RegistryKey<T> registryKey) {
+        final org.bukkit.Registry<T> registry = RegistryAccess.registryAccess().getRegistry(registryKey);
+        final T anyElement = registry.iterator().next();
+        assertInstanceOf(FeatureDependant.class, anyElement, "Registry " + registryKey + " doesn't have feature dependent elements");
+        final FeatureDependant dependant = ((FeatureDependant) anyElement);
+        assertDoesNotThrow(dependant::requiredFeatures, "Failed to get required features for " + anyElement + " in " + registryKey);
+    }
+
+    static Stream<RegistryKey<?>> nonFeatureFilteredRegistries() {
+        return RegistryHelper.getRegistry().registries().filter(r -> {
+            final RegistryEntry<?, ?> entry = PaperRegistries.getEntry(r.key());
+            // has an API registry and isn't a filtered registry
+            return entry != null && !FeatureElement.FILTERED_REGISTRIES.contains(r.key());
+        }).map(r -> PaperRegistries.getEntry(r.key()).apiKey());
+    }
+
+
+    @MethodSource("nonFeatureFilteredRegistries")
+    @ParameterizedTest
+    <T extends Keyed> void testApiDoesntImplementFeatureDependant(final RegistryKey<T> registryKey) {
+        final org.bukkit.Registry<T> registry = RegistryAccess.registryAccess().getRegistry(registryKey);
+        final T anyElement = registry.iterator().next();
+        assertFalse(anyElement instanceof FeatureDependant, "Registry " + registryKey + " has feature dependent elements");
+    }
+}