Reintroduce namespace filtering for mapping trees

Should be a simple optimisation to avoid reading an
additional ns.

src/main/java/dev/architectury/loom/util/MappingOption.java

@@ -1,11 +1,32 @@
 package dev.architectury.loom.util;
 
+import org.jetbrains.annotations.Nullable;
+
 import net.fabricmc.loom.api.LoomGradleExtensionAPI;
+import net.fabricmc.loom.api.mappings.layered.MappingsNamespace;
 
 public enum MappingOption {
-	DEFAULT,
-	WITH_SRG,
-	WITH_MOJANG;
+	DEFAULT(null),
+	WITH_SRG(MappingsNamespace.SRG.toString()),
+	WITH_MOJANG(MappingsNamespace.MOJANG.toString());
+
+	private final String extraNamespace;
+
+	MappingOption(@Nullable String extraNamespace) {
+		this.extraNamespace = extraNamespace;
+	}
+
+	public MappingOption forNamespaces(String... namespaces) {
+		if (extraNamespace == null) return this;
+
+		for (String namespace : namespaces) {
+			if (extraNamespace.equals(namespace)) {
+				return this;
+			}
+		}
+
+		return DEFAULT;
+	}
 
 	public static MappingOption forPlatform(LoomGradleExtensionAPI extension) {
 		return switch (extension.getPlatform().get()) {

src/main/java/net/fabricmc/loom/util/TinyRemapperHelper.java

@@ -71,8 +71,7 @@ public static TinyRemapper getTinyRemapper(Project project, SharedServiceManager
 
 	public static TinyRemapper getTinyRemapper(Project project, SharedServiceManager serviceManager, String fromM, String toM, boolean fixRecords, Consumer<TinyRemapper.Builder> builderConsumer, Set<String> fromClassNames) throws IOException {
 		LoomGradleExtension extension = LoomGradleExtension.get(project);
-		// TODO (Neo): Bring back the fromM.equals(srg) || toM.equals(srg) check, also for mojang ns?
-		final MappingOption mappingOption = MappingOption.forPlatform(extension);
+		final MappingOption mappingOption = MappingOption.forPlatform(extension).forNamespaces(fromM, toM);
 		MemoryMappingTree mappingTree = extension.getMappingConfiguration().getMappingsService(serviceManager, mappingOption).getMappingTree();
 
 		if (fixRecords && !mappingTree.getSrcNamespace().equals(fromM)) {

src/test/groovy/net/fabricmc/loom/test/unit/architectury/MappingOptionTest.groovy

@@ -0,0 +1,49 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2023 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.test.unit.architectury
+
+import spock.lang.Specification
+
+import static dev.architectury.loom.util.MappingOption.*
+
+class MappingOptionTest extends Specification {
+	def "namespace filtering with empty array should not change mapping option"() {
+		when:
+		def filtered = mappingOption.forNamespaces(namespaces as String[])
+		then:
+		filtered == expected
+		where:
+		mappingOption | namespaces      | expected
+		DEFAULT       | []              | DEFAULT
+		WITH_MOJANG   | []              | DEFAULT
+		WITH_SRG      | []              | DEFAULT
+		DEFAULT       | ['a', 'srg']    | DEFAULT
+		WITH_SRG      | ['a', 'srg']    | WITH_SRG
+		WITH_MOJANG   | ['a', 'srg']    | DEFAULT
+		DEFAULT       | ['mojang', 'a'] | DEFAULT
+		WITH_SRG      | ['mojang', 'a'] | DEFAULT
+		WITH_MOJANG   | ['mojang', 'a'] | WITH_MOJANG
+	}
+}