Use linked resource instead of filesystem

org.eclipse.jdt.ls.core/src/org/eclipse/jdt/ls/core/internal/managers/LinkResourceUtil.java

@@ -0,0 +1,137 @@
+/*******************************************************************************
+ * Copyright (c) 2023 Red Hat, Inc. and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License 2.0
+ * which accompanies this distribution, and is available at
+ * https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *******************************************************************************/
+package org.eclipse.jdt.ls.core.internal.managers;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.StandardCopyOption;
+import java.nio.file.StandardOpenOption;
+import java.nio.file.attribute.BasicFileAttributeView;
+import java.time.Instant;
+import java.time.temporal.ChronoUnit;
+import java.util.stream.Stream;
+
+import org.eclipse.core.internal.preferences.EclipsePreferences;
+import org.eclipse.core.resources.IFile;
+import org.eclipse.core.resources.IFolder;
+import org.eclipse.core.resources.IProject;
+import org.eclipse.core.resources.IProjectDescription;
+import org.eclipse.core.resources.IResource;
+import org.eclipse.core.resources.ResourcesPlugin;
+import org.eclipse.core.runtime.CoreException;
+import org.eclipse.core.runtime.IPath;
+import org.eclipse.core.runtime.NullProgressMonitor;
+import org.eclipse.core.runtime.Platform;
+import org.eclipse.core.runtime.Status;
+import org.eclipse.jdt.core.IJavaProject;
+
+class LinkResourceUtil {
+
+	private static final IPath METADATA_FOLDER_PATH = ResourcesPlugin.getWorkspace().getRoot().getLocation().append(".projects");
+
+	private static boolean isNewer(Path file, Instant instant) throws CoreException {
+		try {
+			Instant creationInstant = Files.getFileAttributeView(file, BasicFileAttributeView.class).readAttributes().creationTime().toInstant();
+			// match accuracy
+			ChronoUnit smallestSupportedUnit = Stream.of(ChronoUnit.NANOS, ChronoUnit.MILLIS, ChronoUnit.SECONDS) // IMPORTANT: keeps units in Stream from finer to coarser
+				.filter(creationInstant::isSupported).filter(instant::isSupported) //
+				.findFirst().orElse(null);
+			if (Platform.OS_MACOSX.equals(Platform.getOS())) {
+				// macOS filesystem has second-only accuracy (despite Instant.isSupported returns)
+				smallestSupportedUnit = ChronoUnit.SECONDS;
+			}
+			if (smallestSupportedUnit != null) {
+				creationInstant.truncatedTo(smallestSupportedUnit);
+				instant.truncatedTo(smallestSupportedUnit);
+			} else {
+				throw new CoreException(Status.error("No supported time unit!"));
+			}
+			return creationInstant.equals(instant) || creationInstant.isAfter(instant);
+		} catch (IOException ex) {
+			throw new CoreException(Status.error(ex.getMessage(), ex));
+		}
+	}
+
+    /**
+     * Get the redirected path of the input path. The path will be redirected to
+     * the workspace's metadata folder ({@link LinkResourceUtil#METADATA_FOLDER_PATH}).
+     * @param projectName name of the project.
+     * @param path path needs to be redirected.
+     * @return the redirected path.
+     */
+    private static IPath getMetaDataFilePath(String projectName, IPath path) {
+        if (path.segmentCount() == 1) {
+            return METADATA_FOLDER_PATH.append(projectName).append(path);
+        }
+
+        String lastSegment = path.lastSegment();
+        if (IProjectDescription.DESCRIPTION_FILE_NAME.equals(lastSegment)) {
+            return METADATA_FOLDER_PATH.append(projectName).append(lastSegment);
+        }
+
+        return null;
+    }
+
+	private static void linkFolderIfNewer(IFolder settingsFolder, Instant instant) throws CoreException {
+		if (settingsFolder.isLinked()) {
+			return;
+		}
+		if (settingsFolder.exists() && !isNewer(settingsFolder.getLocation().toPath(), instant)) {
+			return;
+		}
+		if (!settingsFolder.exists()) {
+			// not existing yet, create link
+			File diskFolder = getMetaDataFilePath(settingsFolder.getProject().getName(), settingsFolder.getProjectRelativePath()).toFile();
+			diskFolder.mkdirs();
+			settingsFolder.createLink(diskFolder.toURI(), IResource.NONE, new NullProgressMonitor());
+		} else if (isNewer(settingsFolder.getLocation().toPath(), instant)) {
+			// already existing but not existing before import: move then link
+			File sourceFolder = settingsFolder.getLocation().toFile();
+			File targetFolder = getMetaDataFilePath(settingsFolder.getProject().getName(), settingsFolder.getProjectRelativePath()).toFile();
+			File parentTargetFolder = targetFolder.getParentFile();
+			if (!parentTargetFolder.isDirectory()) {
+				parentTargetFolder.mkdirs();
+			}
+			sourceFolder.renameTo(targetFolder);
+			settingsFolder.createLink(targetFolder.toURI(), IResource.REPLACE, new NullProgressMonitor());
+		}
+	}
+
+	private static void linkFileIfNewer(IFile metadataFile, Instant instant, String ifEmpty) throws CoreException {
+		if (metadataFile.isLinked()) {
+			return;
+		}
+		if (metadataFile.exists() && !isNewer(metadataFile.getLocation().toPath(), instant)) {
+			return;
+		}
+		File targetFile = getMetaDataFilePath(metadataFile.getProject().getName(), metadataFile.getProjectRelativePath()).toFile();
+		targetFile.getParentFile().mkdirs();
+		try {
+			if (metadataFile.exists()) {
+				Files.move(metadataFile.getLocation().toFile().toPath(), targetFile.toPath(), StandardCopyOption.REPLACE_EXISTING);
+			} else {
+				Files.writeString(targetFile.toPath(), ifEmpty != null ? ifEmpty : "", StandardOpenOption.CREATE);
+			}
+		} catch (IOException ex) {
+			throw new CoreException(Status.error(ex.getMessage(), ex));
+		}
+		metadataFile.createLink(targetFile.toURI(), IResource.REPLACE, new NullProgressMonitor());
+	}
+
+	public static void linkMetadataResourcesIfNewer(IProject project, Instant instant) throws CoreException {
+		linkFileIfNewer(project.getFile(IProjectDescription.DESCRIPTION_FILE_NAME), instant, null);
+		linkFolderIfNewer(project.getFolder(EclipsePreferences.DEFAULT_PREFERENCES_DIRNAME), instant);
+		linkFileIfNewer(project.getFile(IJavaProject.CLASSPATH_FILE_NAME), instant, null);
+		linkFileIfNewer(project.getFile(".factorypath"), instant, "<factorypath/>");
+	}
+
+}

org.eclipse.jdt.ls.core/src/org/eclipse/jdt/ls/core/internal/managers/ProjectsManager.java

@@ -17,16 +17,19 @@
 
 import java.io.File;
 import java.net.URI;
+import java.time.Instant;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
+import java.util.Map.Entry;
 import java.util.Objects;
 import java.util.Optional;
+import java.util.Set;
 import java.util.TreeMap;
-import java.util.Map.Entry;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
@@ -145,6 +148,8 @@ private void updateEncoding(IProgressMonitor monitor) throws CoreException {
 	protected void importProjects(Collection<IPath> rootPaths, IProgressMonitor monitor) throws CoreException, OperationCanceledException {
 		SubMonitor subMonitor = SubMonitor.convert(monitor, rootPaths.size() * 100);
 		MultiStatus importStatusCollection = new MultiStatus(IConstants.PLUGIN_ID, -1, "Failed to import projects", null);
+		IProject[] alreadyExistingProjects = ProjectsManager.getWorkspaceRoot().getProjects();
+		Instant importSessionStart = Instant.now();
 		for (IPath rootPath : rootPaths) {
 			File rootFolder = rootPath.toFile();
 			try {
@@ -163,6 +168,18 @@ protected void importProjects(Collection<IPath> rootPaths, IProgressMonitor moni
 				JavaLanguageServerPlugin.logException("Failed to import projects", e);
 			}
 		}
+		if (!generatesMetadataFilesAtProjectRoot()) {
+			Set<IProject> newProjects = new HashSet<>(Arrays.asList(getWorkspaceRoot().getProjects()));
+			newProjects.removeAll(Arrays.asList(alreadyExistingProjects));
+			for (IProject project : newProjects) {
+				try {
+					LinkResourceUtil.linkMetadataResourcesIfNewer(project, importSessionStart);
+				} catch (CoreException e) {
+					importStatusCollection.add(e.getStatus());
+					JavaLanguageServerPlugin.logException("Failed to import projects", e);
+				}
+			}
+		}
 		if (!importStatusCollection.isOK()) {
 			throw new CoreException(importStatusCollection);
 		}
@@ -349,10 +366,29 @@ public static IProject createJavaProject(IProject project, IProgressMonitor moni
 		return createJavaProject(project, null, "src", "bin", monitor);
 	}
 
+	/*
+	 * ⚠ These value is duplicated in ProjectsManager as both bundles must remain independent,
+	 * but the same dir should be used for .project or .settings/.classpath.
+	 * So when updating one, think about updating the other.
+	 */
+	public static final String GENERATES_METADATA_FILES_AT_PROJECT_ROOT = "java.import.generatesMetadataFilesAtProjectRoot";
+
+	/**
+	 * Check whether the metadata files needs to be generated at project root.
+	 */
+	public static boolean generatesMetadataFilesAtProjectRoot() {
+		String property = System.getProperty(GENERATES_METADATA_FILES_AT_PROJECT_ROOT);
+		if (property == null) {
+			return true;
+		}
+		return Boolean.parseBoolean(property);
+	}
+
 	public static IProject createJavaProject(IProject project, IPath projectLocation, String src, String bin, IProgressMonitor monitor) throws CoreException, OperationCanceledException {
 		if (project.exists()) {
 			return project;
 		}
+		Instant creationRequestInstant = Instant.now();
 		JavaLanguageServerPlugin.logInfo("Creating the Java project " + project.getName());
 		//Create project
 		IProjectDescription description = ResourcesPlugin.getWorkspace().newProjectDescription(project.getName());
@@ -400,6 +436,10 @@ public static IProject createJavaProject(IProject project, IPath projectLocation
 		//Add JVM to project class path
 		javaProject.setRawClasspath(classpaths.toArray(new IClasspathEntry[0]), monitor);
 
+		if (!generatesMetadataFilesAtProjectRoot()) {
+			LinkResourceUtil.linkMetadataResourcesIfNewer(project, creationRequestInstant);
+		}
+
 		JavaLanguageServerPlugin.logInfo("Finished creating the Java project " + project.getName());
 		return project;
 	}
@@ -434,6 +474,7 @@ public IStatus runInWorkspace(IProgressMonitor monitor) {
 					updateEncoding(monitor);
 					project.deleteMarkers(BUILD_FILE_MARKER_TYPE, false, IResource.DEPTH_ONE);
 					long elapsed = System.currentTimeMillis() - start;
+					replaceLinkedMetadataWithLocal(project);
 					JavaLanguageServerPlugin.logInfo("Updated " + projectName + " in " + elapsed + " ms");
 				} catch (Exception e) {
 					String msg = "Error updating " + projectName;
@@ -641,6 +682,13 @@ public void reportProjectsStatus() {
 			JavaLanguageServerPlugin.sendStatus(ServiceStatus.ProjectStatus, "OK");
 		}
 	}
+
+	private void replaceLinkedMetadataWithLocal(IProject p) throws CoreException {
+		if (new File(p.getLocation().toFile(), IJavaProject.CLASSPATH_FILE_NAME).exists() &&
+			p.getFile(IJavaProject.CLASSPATH_FILE_NAME).isLinked()) {
+			p.getFile(IJavaProject.CLASSPATH_FILE_NAME).delete(false, false, null);
+		}
+	}
 
 	class UpdateProjectsWorkspaceJob extends WorkspaceJob {