Add FeatureSet class holding information about mapping format capab…

…ilities (#92)

CHANGELOG.md

@@ -4,6 +4,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
+- Added `MappingFormat#features()` to allow for more fine-grained programmatic querying of format capabilities
 - Overhauled the internal `ColumnFileReader` to behave more consistently
 - Made handling of the `NEEDS_MULTIPLE_PASSES` flag more consistent, reducing memory usage in a few cases
 - Made some internal methods in Enigma and TSRG readers actually private

src/main/java/net/fabricmc/mappingio/MappingReader.java

@@ -161,7 +161,7 @@ public static List<String> getNamespaces(Path file, MappingFormat format) throws
 			if (format == null) throw new IOException("invalid/unsupported mapping format");
 		}
 
-		if (format.hasNamespaces) {
+		if (format.features().hasNamespaces()) {
 			try (Reader reader = Files.newBufferedReader(file)) {
 				return getNamespaces(reader, format);
 			}
@@ -183,7 +183,7 @@ public static List<String> getNamespaces(Reader reader, MappingFormat format) th
 			if (format == null) throw new IOException("invalid/unsupported mapping format");
 		}
 
-		if (format.hasNamespaces) {
+		if (format.features().hasNamespaces()) {
 			checkReaderCompatible(format);
 
 			switch (format) {

src/main/java/net/fabricmc/mappingio/format/FeatureSet.java

@@ -0,0 +1,101 @@
+/*
+ * Copyright (c) 2024 FabricMC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package net.fabricmc.mappingio.format;
+
+public interface FeatureSet {
+	boolean hasNamespaces();
+	MetadataSupport fileMetadata();
+	MetadataSupport elementMetadata();
+	NameSupport packages();
+	NameSupport classes();
+	MemberSupport fields();
+	MemberSupport methods();
+	LocalSupport args();
+	LocalSupport vars();
+	ElementCommentSupport elementComments();
+	boolean hasFileComments();
+
+	default boolean supportsPackages() {
+		return packages().srcNames() != FeaturePresence.ABSENT
+				|| packages().dstNames() != FeaturePresence.ABSENT;
+	}
+
+	default boolean supportsClasses() {
+		return classes().srcNames() != FeaturePresence.ABSENT
+				|| classes().dstNames() != FeaturePresence.ABSENT;
+	}
+
+	default boolean supportsFields() {
+		return FeatureSetHelper.isSupported(fields());
+	}
+
+	default boolean supportsMethods() {
+		return FeatureSetHelper.isSupported(methods());
+	}
+
+	default boolean supportsArgs() {
+		return FeatureSetHelper.isSupported(args());
+	}
+
+	default boolean supportsVars() {
+		return FeatureSetHelper.isSupported(vars());
+	}
+
+	enum MetadataSupport {
+		/** No metadata at all. */
+		NONE,
+
+		/** Only some select properties.  */
+		FIXED,
+
+		/** Arbitrary metadata may be attached. */
+		ARBITRARY
+	}
+
+	enum FeaturePresence {
+		REQUIRED,
+		OPTIONAL,
+		ABSENT
+	}
+
+	interface NameSupport {
+		FeaturePresence srcNames();
+		FeaturePresence dstNames();
+	}
+
+	interface DescSupport {
+		FeaturePresence srcDescs();
+		FeaturePresence dstDescs();
+	}
+
+	interface MemberSupport extends NameSupport, DescSupport {
+	}
+
+	interface LocalSupport extends NameSupport, DescSupport {
+		FeaturePresence positions();
+		FeaturePresence lvIndices();
+		FeaturePresence lvtRowIndices();
+		FeaturePresence startOpIndices();
+		FeaturePresence endOpIndices();
+	}
+
+	enum ElementCommentSupport {
+		NAMESPACED,
+		SHARED,
+		NONE
+	}
+}