Make data generation .cache reproducible

fabric-data-generation-api-v1/src/main/java/net/fabricmc/fabric/mixin/datagen/DataCacheCachedDataMixin.java

@@ -0,0 +1,48 @@
+/*
+ * Copyright (c) 2016, 2017, 2018, 2019 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.fabric.mixin.datagen;
+
+import java.nio.file.Path;
+import java.util.Comparator;
+import java.util.Map;
+
+import com.google.common.collect.ImmutableSet;
+import com.google.common.hash.HashCode;
+import com.llamalad7.mixinextras.injector.ModifyExpressionValue;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Unique;
+import org.spongepowered.asm.mixin.injection.At;
+
+@Mixin(targets = "net.minecraft.data.DataCache$CachedData")
+public abstract class DataCacheCachedDataMixin {
+	@ModifyExpressionValue(method = "write", at = @At(value = "INVOKE", target = "Lcom/google/common/collect/ImmutableMap;entrySet()Lcom/google/common/collect/ImmutableSet;"))
+	private ImmutableSet<Map.Entry<Path, HashCode>> sortPaths(ImmutableSet<Map.Entry<Path, HashCode>> original) {
+		return original.stream()
+				.sorted(Map.Entry.comparingByKey(Comparator.comparing(k -> normalizePath(k.toString()))))
+				.collect(ImmutableSet.toImmutableSet());
+	}
+
+	@ModifyExpressionValue(method = "write", at = @At(value = "INVOKE", target = "Ljava/nio/file/Path;toString()Ljava/lang/String;"))
+	private String pathToString(String original) {
+		return normalizePath(original);
+	}
+
+	@Unique
+	private static String normalizePath(String path) {
+		return path.replace('\\', '/');
+	}
+}

fabric-data-generation-api-v1/src/main/java/net/fabricmc/fabric/mixin/datagen/DataCacheMixin.java

@@ -0,0 +1,35 @@
+/*
+ * Copyright (c) 2016, 2017, 2018, 2019 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.fabric.mixin.datagen;
+
+import java.time.LocalDateTime;
+
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Redirect;
+
+import net.minecraft.data.DataCache;
+
+@Mixin(DataCache.class)
+public abstract class DataCacheMixin {
+	// Lambda in write()V
+	@Redirect(method = "method_46571", at = @At(value = "INVOKE", target = "Ljava/time/LocalDateTime;now()Ljava/time/LocalDateTime;"))
+	private LocalDateTime constantTime() {
+		// Write a constant time to the .cache file to ensure datagen output is reproducible
+		return LocalDateTime.MIN;
+	}
+}

fabric-data-generation-api-v1/src/main/resources/fabric-data-generation-api-v1.mixins.json

@@ -3,6 +3,8 @@
   "package": "net.fabricmc.fabric.mixin.datagen",
   "compatibilityLevel": "JAVA_21",
   "mixins": [
+    "DataCacheCachedDataMixin",
+    "DataCacheMixin",
     "DataProviderMixin",
     "TagBuilderMixin",
     "TagProviderMixin",