Add MissingSrcFilter

src/main/java/net/fabricmc/mappingio/adapter/MissingSrcFilter.java

@@ -0,0 +1,60 @@
+/*
+ * Copyright (c) 2021 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.adapter;
+
+import java.io.IOException;
+
+import net.fabricmc.mappingio.tree.MemoryMappingTree;
+
+public class MissingSrcFilter extends ForwardingMappingVisitor {
+	public MissingSrcFilter(MemoryMappingTree next) {
+		super(next);
+
+		this.next = next;
+	}
+
+	@Override
+	public boolean visitClass(String srcName) throws IOException {
+		if (next.getClass(srcName) != null) {
+			this.classSrcName = srcName;
+			return super.visitClass(srcName);
+		}
+
+		return false;
+	}
+
+	@Override
+	public boolean visitField(String srcName, String srcDesc) throws IOException {
+		if (next.getField(this.classSrcName, srcName, srcDesc) != null) {
+			return super.visitField(srcName, srcDesc);
+		}
+
+		return false;
+	}
+
+	@Override
+	public boolean visitMethod(String srcName, String srcDesc) throws IOException {
+		if (next.getMethod(this.classSrcName, srcName, srcDesc) != null) {
+			return super.visitMethod(srcName, srcDesc);
+		}
+
+		return false;
+	}
+
+	protected final MemoryMappingTree next;
+	protected String classSrcName;
+}