Add error recovery

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

@@ -28,6 +28,9 @@
 
 import org.jetbrains.annotations.Nullable;
 
+import net.fabricmc.mappingio.format.ErrorCollector;
+import net.fabricmc.mappingio.format.ErrorCollector.Severity;
+import net.fabricmc.mappingio.format.ErrorCollector.ThrowingErrorCollector;
 import net.fabricmc.mappingio.format.MappingFormat;
 import net.fabricmc.mappingio.format.enigma.EnigmaDirReader;
 import net.fabricmc.mappingio.format.enigma.EnigmaFileReader;
@@ -184,10 +187,23 @@ public static List<String> getNamespaces(Reader reader, MappingFormat format) th
 	 * @param visitor The receiving visitor.
 	 * @throws IOException If the format can't be detected or reading fails.
 	 */
+	@Deprecated
 	public static void read(Path path, MappingVisitor visitor) throws IOException {
 		read(path, null, visitor);
 	}
 
+	/**
+	 * Tries to detect the format of the given path and read it.
+	 *
+	 * @param path The path to read from. Can be a file or a directory.
+	 * @param visitor The receiving visitor.
+	 * @param errorCollector The error collector instance to log errors to.
+	 * @throws IOException If the format can't be detected or reading fails.
+	 */
+	public static void read(Path path, MappingVisitor visitor, ErrorCollector errorCollector) throws IOException {
+		read(path, null, visitor, errorCollector);
+	}
+
 	/**
 	 * Tries to read the given path using the passed format's reader.
 	 *
@@ -196,20 +212,33 @@ public static void read(Path path, MappingVisitor visitor) throws IOException {
 	 * @param visitor The receiving visitor.
 	 * @throws IOException If reading fails.
 	 */
+	@Deprecated
 	public static void read(Path path, MappingFormat format, MappingVisitor visitor) throws IOException {
+		read(path, format, visitor, new ThrowingErrorCollector(Severity.ERROR));
+	}
+
+	/**
+	 * Tries to read the given path using the passed format's reader.
+	 *
+	 * @param path The path to read from. Can be a file or a directory.
+	 * @param format The format to use. Has to match the path's format.
+	 * @param visitor The receiving visitor.
+	 * @throws IOException If reading fails.
+	 */
+	public static void read(Path path, MappingFormat format, MappingVisitor visitor, ErrorCollector errorCollector) throws IOException {
 		if (format == null) {
 			format = detectFormat(path);
 			if (format == null) throw new IOException("invalid/unsupported mapping format");
 		}
 
 		if (format.hasSingleFile()) {
 			try (Reader reader = Files.newBufferedReader(path)) {
-				read(reader, format, visitor);
+				read(reader, format, visitor, errorCollector);
 			}
 		} else {
 			switch (format) {
 			case ENIGMA_DIR:
-				EnigmaDirReader.read(path, visitor);
+				EnigmaDirReader.read(path, visitor, errorCollector);
 				break;
 			default:
 				throw new IllegalStateException();
@@ -224,10 +253,23 @@ public static void read(Path path, MappingFormat format, MappingVisitor visitor)
 	 * @param visitor The receiving visitor.
 	 * @throws IOException If the format can't be detected or reading fails.
 	 */
+	@Deprecated
 	public static void read(Reader reader, MappingVisitor visitor) throws IOException {
 		read(reader, null, visitor);
 	}
 
+	/**
+	 * Tries to detect the reader's content's format and read it.
+	 *
+	 * @param reader The reader to read from.
+	 * @param visitor The receiving visitor.
+	 * @param errorCollector The error collector instance to log errors to.
+	 * @throws IOException If the format can't be detected or reading fails.
+	 */
+	public static void read(Reader reader, MappingVisitor visitor, ErrorCollector errorCollector) throws IOException {
+		read(reader, null, visitor, errorCollector);
+	}
+
 	/**
 	 * Tries to read the reader's content using the passed format's mapping reader.
 	 *
@@ -236,7 +278,21 @@ public static void read(Reader reader, MappingVisitor visitor) throws IOExceptio
 	 * @param visitor The receiving visitor.
 	 * @throws IOException If reading fails.
 	 */
+	@Deprecated
 	public static void read(Reader reader, MappingFormat format, MappingVisitor visitor) throws IOException {
+		read(reader, format, visitor, new ThrowingErrorCollector(Severity.ERROR));
+	}
+
+	/**
+	 * Tries to read the reader's content using the passed format's mapping reader.
+	 *
+	 * @param reader The reader to read from.
+	 * @param format The format to use. Has to match the reader's content's format.
+	 * @param visitor The receiving visitor.
+	 * @param errorCollector The error collector instance to log errors to.
+	 * @throws IOException If reading fails.
+	 */
+	public static void read(Reader reader, MappingFormat format, MappingVisitor visitor, ErrorCollector errorCollector) throws IOException {
 		if (format == null) {
 			if (!reader.markSupported()) reader = new BufferedReader(reader);
 			reader.mark(DETECT_HEADER_LEN);
@@ -249,25 +305,25 @@ public static void read(Reader reader, MappingFormat format, MappingVisitor visi
 
 		switch (format) {
 		case TINY_FILE:
-			Tiny1FileReader.read(reader, visitor);
+			Tiny1FileReader.read(reader, visitor, errorCollector);
 			break;
 		case TINY_2_FILE:
-			Tiny2FileReader.read(reader, visitor);
+			Tiny2FileReader.read(reader, visitor, errorCollector);
 			break;
 		case ENIGMA_FILE:
-			EnigmaFileReader.read(reader, visitor);
+			EnigmaFileReader.read(reader, visitor, errorCollector);
 			break;
 		case SRG_FILE:
 		case XSRG_FILE:
-			SrgFileReader.read(reader, visitor);
+			SrgFileReader.read(reader, visitor, errorCollector);
 			break;
 		case CSRG_FILE:
 		case TSRG_FILE:
 		case TSRG_2_FILE:
-			TsrgFileReader.read(reader, visitor);
+			TsrgFileReader.read(reader, visitor, errorCollector);
 			break;
 		case PROGUARD_FILE:
-			ProGuardFileReader.read(reader, visitor);
+			ProGuardFileReader.read(reader, visitor, errorCollector);
 			break;
 		default:
 			throw new IllegalStateException();

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

@@ -0,0 +1,116 @@
+/*
+ * Copyright (c) 2023 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;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+import org.jetbrains.annotations.ApiStatus;
+
+public interface ErrorCollector {
+	static ErrorCollector create() {
+		return new ErrorCollector() {
+			@Override
+			public void add(Severity severity, String message) throws IOException {
+				errors.add(new ParsingError(severity, message));
+			}
+
+			@Override
+			public List<ParsingError> getErrors() {
+				return errors;
+			}
+
+			private final List<ParsingError> errors = new ArrayList<>();
+		};
+	}
+
+	default void addInfo(String message) throws IOException {
+		add(Severity.INFO, message);
+	}
+
+	default void addWarning(String message) throws IOException {
+		add(Severity.WARNING, message);
+	}
+
+	default void addError(String message) throws IOException {
+		add(Severity.ERROR, message);
+	}
+
+	void add(Severity severity, String message) throws IOException;
+
+	List<ParsingError> getErrors();
+
+	enum Severity {
+		/**
+		 * When something's technically wrong but doesn't affect
+		 * parsing or the mapping data in any way.
+		 */
+		INFO,
+		/**
+		 * When element data is partially missing, but the rest of the element
+		 * could still be deciphered and it didn't have to be skipped entirely.
+		 * Or when an unknown top-level element is encountered.
+		 */
+		WARNING,
+		/**
+		 * An issue so severe that parsing of entire elements had to be skipped.
+		 * E.g. a class's/member's source name being absent.
+		 */
+		ERROR
+	}
+
+	class ParsingError {
+		ParsingError(Severity severity, String message) {
+			this.severity = severity;
+			this.message = message;
+		}
+
+		public Severity getSeverity() {
+			return severity;
+		}
+
+		public String getMessage() {
+			return message;
+		}
+
+		private final Severity severity;
+		private final String message;
+	}
+
+	@ApiStatus.Internal
+	class ThrowingErrorCollector implements ErrorCollector {
+		public ThrowingErrorCollector(Severity severityToThrowAt) {
+			this.severityToThrowAt = severityToThrowAt;
+		}
+
+		@Override
+		public void add(Severity severity, String message) throws IOException {
+			if (severity.compareTo(severityToThrowAt) >= 0) {
+				throw new IOException(message);
+			}
+		}
+
+		@Override
+		public List<ParsingError> getErrors() {
+			return Collections.emptyList();
+		}
+
+		private Severity severityToThrowAt;
+	}
+}

src/main/java/net/fabricmc/mappingio/format/enigma/EnigmaDirReader.java

@@ -29,6 +29,9 @@
 import net.fabricmc.mappingio.MappingUtil;
 import net.fabricmc.mappingio.MappingVisitor;
 import net.fabricmc.mappingio.adapter.ForwardingMappingVisitor;
+import net.fabricmc.mappingio.format.ErrorCollector;
+import net.fabricmc.mappingio.format.ErrorCollector.Severity;
+import net.fabricmc.mappingio.format.ErrorCollector.ThrowingErrorCollector;
 import net.fabricmc.mappingio.format.MappingFormat;
 import net.fabricmc.mappingio.tree.MappingTree;
 import net.fabricmc.mappingio.tree.MemoryMappingTree;
@@ -43,11 +46,21 @@ public final class EnigmaDirReader {
 	private EnigmaDirReader() {
 	}
 
+	@Deprecated
 	public static void read(Path dir, MappingVisitor visitor) throws IOException {
 		read(dir, MappingUtil.NS_SOURCE_FALLBACK, MappingUtil.NS_TARGET_FALLBACK, visitor);
 	}
 
+	public static void read(Path dir, MappingVisitor visitor, ErrorCollector errorCollector) throws IOException {
+		read(dir, MappingUtil.NS_SOURCE_FALLBACK, MappingUtil.NS_TARGET_FALLBACK, visitor, errorCollector);
+	}
+
+	@Deprecated
 	public static void read(Path dir, String sourceNs, String targetNs, MappingVisitor visitor) throws IOException {
+		read(dir, sourceNs, targetNs, visitor, new ThrowingErrorCollector(Severity.ERROR));
+	}
+
+	public static void read(Path dir, String sourceNs, String targetNs, MappingVisitor visitor, ErrorCollector errorCollector) throws IOException {
 		Set<MappingFlag> flags = visitor.getFlags();
 		MappingVisitor parentVisitor = null;
 
@@ -89,7 +102,7 @@ public boolean visitEnd() throws IOException {
 			@Override
 			public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
 				if (file.getFileName().toString().endsWith("." + MappingFormat.ENIGMA_FILE.fileExt)) {
-					EnigmaFileReader.read(Files.newBufferedReader(file), sourceNs, targetNs, delegatingVisitor);
+					EnigmaFileReader.read(Files.newBufferedReader(file), sourceNs, targetNs, delegatingVisitor, errorCollector);
 				}
 
 				return FileVisitResult.CONTINUE;