Warn when the project is stored in OneDrive

src/main/java/net/fabricmc/loom/LoomGradlePlugin.java

@@ -48,6 +48,7 @@
 import net.fabricmc.loom.task.LoomTasks;
 import net.fabricmc.loom.task.RemapTaskConfiguration;
 import net.fabricmc.loom.util.LibraryLocationLogger;
+import net.fabricmc.loom.util.OneDrive;
 
 public class LoomGradlePlugin implements Plugin<PluginAware> {
 	public static final String NAME = "fabric-loom";
@@ -81,6 +82,7 @@ private void apply(Project project) {
 		project.getLogger().lifecycle("Fabric Loom: " + LOOM_VERSION);
 
 		LibraryLocationLogger.logLibraryVersions();
+		OneDrive.verify(project);
 
 		// Apply default plugins
 		project.apply(Map.of("plugin", "java-library"));

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

@@ -0,0 +1,91 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2025 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.util;
+
+import java.nio.file.InvalidPathException;
+import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.function.Supplier;
+
+import org.gradle.api.Project;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+// OneDrive causes all kinds of issues, log a warning if the users project is stored there.
+public final class OneDrive {
+	private static final List<String> ENV_VARS = List.of("OneDrive", "OneDriveConsumer", "OneDriveCommercial");
+	private static final Supplier<List<Path>> ONE_DRIVE_PATHS = Lazy.of(OneDrive::getOneDrivePaths);
+	private static final Logger LOGGER = LoggerFactory.getLogger(OneDrive.class);
+
+	private OneDrive() {
+	}
+
+	public static void verify(Project project) {
+		if (!Platform.CURRENT.getOperatingSystem().isWindows()) {
+			return;
+		}
+
+		Path projectDir = project.getProjectDir().toPath();
+
+		if (isInOneDrive(projectDir)) {
+			LOGGER.warn("Project directory '{}' is located in OneDrive. This is known to cause issues and slower performance. Consider moving the project to a different location.", projectDir);
+		}
+	}
+
+	private static boolean isInOneDrive(Path path) {
+		Path normalized = path.toAbsolutePath().normalize();
+
+		for (Path oneDrivePath : ONE_DRIVE_PATHS.get()) {
+			if (normalized.startsWith(oneDrivePath)) {
+				return true;
+			}
+		}
+
+		return false;
+	}
+
+	private static List<Path> getOneDrivePaths() {
+		var paths = new ArrayList<Path>();
+
+		for (String envVar : ENV_VARS) {
+			String value = System.getenv(envVar);
+
+			if (value == null || value.isEmpty()) {
+				continue;
+			}
+
+			try {
+				Path path = Path.of(value);
+				paths.add(path.toAbsolutePath().normalize());
+			} catch (InvalidPathException ignored) {
+				// Don't care
+			}
+		}
+
+		return Collections.unmodifiableList(paths);
+	}
+}