[eclipse-cdt#247] Add .clangd configuration file syntax checker

- Inform the user via markers in the .clangd file when the syntax cannot
be parsed, because this leads to problems in the
ClangdConfigurationFileManager.

bundles/org.eclipse.cdt.lsp.clangd/plugin.xml

@@ -110,5 +110,16 @@
          </command>
       </menuContribution>
    </extension>
+   <extension
+         id="org.eclipse.cdt.lsp.clangd.config.marker"
+         name="Clangd Marker"
+         point="org.eclipse.core.resources.markers">
+      <super
+            type="org.eclipse.core.resources.problemmarker">
+      </super>
+      <persistent
+            value="true">
+      </persistent>
+   </extension>   
 
 </plugin>

bundles/org.eclipse.cdt.lsp.clangd/src/org/eclipse/cdt/lsp/internal/clangd/ClangdConfigFileChecker.java

@@ -0,0 +1,172 @@
+/*******************************************************************************
+ * Copyright (c) 2024 Bachmann electronic GmbH and others.
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *
+ * Contributors:
+ * Gesa Hentschke (Bachmann electronic GmbH) - initial implementation
+ *******************************************************************************/
+
+package org.eclipse.cdt.lsp.internal.clangd;
+
+import java.io.IOException;
+import java.util.Optional;
+import java.util.regex.Pattern;
+
+import org.eclipse.cdt.lsp.internal.clangd.editor.ClangdPlugin;
+import org.eclipse.core.resources.IFile;
+import org.eclipse.core.resources.IMarker;
+import org.eclipse.core.resources.IResource;
+import org.eclipse.core.runtime.CoreException;
+import org.eclipse.core.runtime.Platform;
+import org.eclipse.jface.text.BadLocationException;
+import org.eclipse.jface.text.IDocument;
+import org.yaml.snakeyaml.Yaml;
+
+/**
+ * Checks the <code>.clangd</code> file for syntax errors and notifies the user via error markers in the file and Problems view.
+ */
+public class ClangdConfigFileChecker {
+	public static final String CLANGD_MARKER = ClangdPlugin.PLUGIN_ID + ".config.marker"; //$NON-NLS-1$
+	private final Pattern pattern = Pattern.compile(".*line (\\d+), column (\\d+).*"); //$NON-NLS-1$
+	private boolean temporaryLoadedFile = false;
+
+	/**
+	 * Checks if the .clangd file contains valid yaml syntax. Adds error marker to the file if not.
+	 * @param configFile
+	 */
+	public void checkConfigFile(IFile configFile) {
+		Yaml yaml = new Yaml();
+		try (var inputStream = configFile.getContents()) {
+			try {
+				removeMarkerFromClangdConfig(configFile);
+				//throws ScannerException and ParserException:
+				yaml.load(inputStream);
+			} catch (Exception yamlException) {
+				addMarkerToClangdConfig(configFile, yamlException);
+			}
+		} catch (IOException | CoreException e) {
+			Platform.getLog(getClass()).error(e.getMessage(), e);
+		}
+	}
+
+	private void addMarkerToClangdConfig(IFile configFile, Exception e) {
+		try {
+			var configMarker = parseYamlException(e, configFile);
+			var marker = configFile.createMarker(CLANGD_MARKER);
+			marker.setAttribute(IMarker.MESSAGE, configMarker.message);
+			marker.setAttribute(IMarker.SEVERITY, IMarker.SEVERITY_ERROR);
+			marker.setAttribute(IMarker.LINE_NUMBER, configMarker.line);
+			marker.setAttribute(IMarker.CHAR_START, configMarker.charStart);
+			marker.setAttribute(IMarker.CHAR_END, configMarker.charEnd);
+		} catch (CoreException core) {
+			Platform.getLog(getClass()).log(core.getStatus());
+		}
+	}
+
+	private class ClangdConfigMarker {
+		public String message;
+		public int line = 1;
+		public int charStart = -1;
+		public int charEnd = -1;
+	}
+
+	/**
+	 * Fetch line and char position information from exception to create a marker for the .clangd file.
+	 * @param e
+	 * @param file
+	 * @return
+	 */
+	private ClangdConfigMarker parseYamlException(Exception e, IFile file) {
+		var marker = new ClangdConfigMarker();
+		marker.message = getErrorMessage(e);
+		var doc = getDocument(file);
+		if (doc == null) {
+			return marker;
+		}
+		int startLine = -1;
+		int endLine = -1;
+		for (var line : toLines(e.getMessage())) {
+			var matcher = pattern.matcher(line);
+			if (matcher.matches()) {
+				var lineInt = Integer.parseInt(matcher.replaceAll("$1")); //$NON-NLS-1$
+				var column = Integer.parseInt(matcher.replaceAll("$2")); //$NON-NLS-1$
+				if (startLine == -1) {
+					startLine = lineInt;
+				} else if (endLine == -1) {
+					endLine = lineInt;
+				}
+				try {
+					if (marker.charStart == -1 && startLine > -1) {
+						var lineOffset = doc.getLineOffset(startLine - 1);
+						marker.charStart = lineOffset + column - 1;
+					} else if (marker.charEnd == -1 && endLine > -1) {
+						var lineOffset = doc.getLineOffset(endLine - 1);
+						marker.charEnd = lineOffset + column - 1;
+					}
+				} catch (BadLocationException bl) {
+					Platform.getLog(getClass()).error(bl.getMessage(), bl);
+				}
+				if (startLine > -1 && endLine > -1)
+					break;
+			}
+		}
+		//check if endChar has been found:
+		if (marker.charEnd == -1) {
+			if (marker.charStart < doc.getLength() - 1) {
+				marker.charEnd = marker.charStart + 1;
+			} else if (marker.charStart == doc.getLength() - 1 && marker.charStart > 0) {
+				marker.charEnd = marker.charStart;
+				marker.charStart--;
+			} else {
+				marker.charStart = 0;
+				marker.charEnd = 1;
+			}
+		}
+		cleanUp(file);
+		if (startLine > -1) {
+			marker.line = startLine;
+		}
+		return marker;
+	}
+
+	private String[] toLines(String message) {
+		return Optional.ofNullable(message).map(m -> m.lines().toArray(String[]::new)).orElse(new String[] {});
+	}
+
+	private String getErrorMessage(Exception e) {
+		return Optional.ofNullable(e.getLocalizedMessage())
+				.map(m -> m.replaceAll("[" + System.lineSeparator() + "]", " ")) //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$
+				.orElse("Unknown yaml error"); //$NON-NLS-1$
+	}
+
+	private void removeMarkerFromClangdConfig(IFile configFile) {
+		try {
+			configFile.deleteMarkers(CLANGD_MARKER, false, IResource.DEPTH_INFINITE);
+		} catch (CoreException e) {
+			Platform.getLog(getClass()).log(e.getStatus());
+		}
+	}
+
+	private IDocument getDocument(IFile file) {
+		IDocument document = FileUtils.getDocumentFromBuffer(file);
+		if (document != null)
+			return document;
+		document = FileUtils.loadFileTemporary(file);
+		if (document != null)
+			temporaryLoadedFile = true;
+		return document;
+	}
+
+	private void cleanUp(IFile file) {
+		if (temporaryLoadedFile) {
+			FileUtils.disconnectTemporaryLoadedFile(file);
+			temporaryLoadedFile = false;
+		}
+	}
+
+}

bundles/org.eclipse.cdt.lsp.clangd/src/org/eclipse/cdt/lsp/internal/clangd/ClangdConfigFileMonitor.java

@@ -0,0 +1,88 @@
+/*******************************************************************************
+ * Copyright (c) 2024 Bachmann electronic GmbH and others.
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *
+ * Contributors:
+ * Gesa Hentschke (Bachmann electronic GmbH) - initial implementation
+ *******************************************************************************/
+
+package org.eclipse.cdt.lsp.internal.clangd;
+
+import java.util.concurrent.ConcurrentLinkedQueue;
+
+import org.eclipse.cdt.lsp.internal.clangd.editor.ClangdPlugin;
+import org.eclipse.core.resources.IFile;
+import org.eclipse.core.resources.IResourceChangeEvent;
+import org.eclipse.core.resources.IResourceChangeListener;
+import org.eclipse.core.resources.IResourceDelta;
+import org.eclipse.core.resources.IWorkspace;
+import org.eclipse.core.resources.WorkspaceJob;
+import org.eclipse.core.runtime.CoreException;
+import org.eclipse.core.runtime.IProgressMonitor;
+import org.eclipse.core.runtime.IStatus;
+import org.eclipse.core.runtime.Status;
+import org.eclipse.ui.statushandlers.StatusManager;
+
+/**
+ * Monitor changes in <code>.clangd</code> files in the workspace and triggers a yaml checker
+ * to add error markers to the <code>.clangd</code> file when the edits causes yaml loader failures.
+ */
+public class ClangdConfigFileMonitor {
+	private static final String CLANGD_CONFIG_FILE = ".clangd"; //$NON-NLS-1$
+	private final ConcurrentLinkedQueue<IFile> pendingFiles = new ConcurrentLinkedQueue<>();
+	private final IWorkspace workspace;
+	private final ClangdConfigFileChecker checker = new ClangdConfigFileChecker();
+
+	private final IResourceChangeListener listener = new IResourceChangeListener() {
+		@Override
+		public void resourceChanged(IResourceChangeEvent event) {
+			if (event.getDelta() != null && event.getType() == IResourceChangeEvent.POST_CHANGE) {
+				try {
+					event.getDelta().accept(delta -> {
+						if ((delta.getKind() == IResourceDelta.ADDED || delta.getKind() == IResourceDelta.REMOVED
+								|| (delta.getFlags() & IResourceDelta.CONTENT) != 0)
+								&& CLANGD_CONFIG_FILE.equals(delta.getResource().getName())) {
+							if (delta.getResource() instanceof IFile file) {
+								pendingFiles.add(file);
+								checkJob.schedule(100);
+							}
+						}
+						return true;
+					});
+				} catch (CoreException e) {
+					StatusManager.getManager().handle(e, ClangdPlugin.PLUGIN_ID);
+				}
+			}
+		}
+	};
+
+	public ClangdConfigFileMonitor(IWorkspace workspace) {
+		this.workspace = workspace;
+	}
+
+	private final WorkspaceJob checkJob = new WorkspaceJob("Check .clangd file") { //$NON-NLS-1$
+
+		@Override
+		public IStatus runInWorkspace(IProgressMonitor monitor) throws CoreException {
+			while (pendingFiles.peek() != null) {
+				checker.checkConfigFile(pendingFiles.poll());
+			}
+			return Status.OK_STATUS;
+		}
+
+	};
+
+	public ClangdConfigFileMonitor start() {
+		workspace.addResourceChangeListener(listener);
+		return this;
+	}
+
+	public void stop() {
+		workspace.removeResourceChangeListener(listener);
+	}
+}

bundles/org.eclipse.cdt.lsp.clangd/src/org/eclipse/cdt/lsp/internal/clangd/FileUtils.java

@@ -0,0 +1,98 @@
+/*******************************************************************************
+ * Copyright (c) 2024 Bachmann electronic GmbH and others.
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *
+ * Contributors:
+ * Gesa Hentschke (Bachmann electronic GmbH) - initial implementation
+ *******************************************************************************/
+
+package org.eclipse.cdt.lsp.internal.clangd;
+
+import java.util.Optional;
+
+import org.eclipse.core.filebuffers.FileBuffers;
+import org.eclipse.core.filebuffers.ITextFileBuffer;
+import org.eclipse.core.filebuffers.ITextFileBufferManager;
+import org.eclipse.core.filebuffers.LocationKind;
+import org.eclipse.core.resources.IFile;
+import org.eclipse.core.resources.IResource;
+import org.eclipse.core.runtime.CoreException;
+import org.eclipse.core.runtime.NullProgressMonitor;
+import org.eclipse.core.runtime.Platform;
+import org.eclipse.jface.text.IDocument;
+
+public class FileUtils {
+
+	private FileUtils() {
+		// do not instantiate
+	}
+
+	/**
+	 * Loads a files document for temporary usage. {@link FileUtils#disconnectTemporaryLoadedFile(IFile)} has to be called on the file after usage!
+	 * @param file
+	 * @return temporary loaded document for the given file or null.
+	 */
+	public static IDocument loadFileTemporary(IFile file) {
+		if (file == null) {
+			return null;
+		}
+		IDocument document = null;
+
+		if (file.getType() == IResource.FILE) {
+			var bufferManager = getBufferManager();
+			if (bufferManager == null)
+				return document;
+			try {
+				bufferManager.connect(file.getFullPath(), LocationKind.IFILE, new NullProgressMonitor());
+			} catch (CoreException e) {
+				Platform.getLog(FileUtils.class).error(e.getMessage(), e);
+				return document;
+			}
+
+			ITextFileBuffer buffer = bufferManager.getTextFileBuffer(file.getFullPath(), LocationKind.IFILE);
+			if (buffer != null) {
+				document = buffer.getDocument();
+			}
+		}
+
+		return document;
+	}
+
+	/**
+	 * When a files document has been obtained via {@link FileUtils#loadFileTemporary(IFile)}, then the file has to be disconnected from it's buffer manager.
+	 * @param file
+	 */
+	public static void disconnectTemporaryLoadedFile(IFile file) {
+		Optional.ofNullable(getBufferManager()).ifPresent(bm -> {
+			try {
+				bm.disconnect(file.getFullPath(), LocationKind.IFILE, new NullProgressMonitor());
+			} catch (CoreException e) {
+				Platform.getLog(FileUtils.class).error(e.getMessage(), e);
+			}
+		});
+	}
+
+	/**
+	 * Tries to fetch the document for the given file. Returns the document when the file is already in the text file buffer or <code>null</code> if not.
+	 * @param file
+	 * @return document for the given file or <code>null</code>
+	 */
+	public static IDocument getDocumentFromBuffer(IFile file) {
+		if (file == null) {
+			return null;
+		}
+		return Optional.ofNullable(getBufferManager())
+				.map(bm -> bm.getTextFileBuffer(file.getFullPath(), LocationKind.IFILE)).map(b -> b.getDocument())
+				.orElse(null);
+	}
+
+	private static ITextFileBufferManager getBufferManager() {
+		return FileBuffers.getTextFileBufferManager();
+	}
+
+}