Add action for requesting signature help

Author: travkin79

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

@@ -79,6 +79,10 @@
             id="org.eclipse.cdt.lsp.clangd.editor.commands.command.getSymbolInfo"
             name="Receive Symbol Info">
       </command>
+      <command
+            id="org.eclipse.cdt.lsp.clangd.editor.commands.command.getSignatureHelp"
+            name="Receive Signature Help">
+      </command>
    </extension>
    <extension
          point="org.eclipse.ui.bindings">
@@ -125,6 +129,18 @@
             </with>
          </activeWhen>
       </handler>
+      <handler
+            class="org.eclipse.cdt.lsp.internal.clangd.editor.handlers.ReceiveSignatureHelpCommandHandler"
+            commandId="org.eclipse.cdt.lsp.clangd.editor.commands.command.getSignatureHelp">
+         <activeWhen>
+            <with
+                  variable="activeEditor">
+               <test
+                     property="org.eclipse.cdt.lsp.editor.active">
+               </test>
+            </with>
+         </activeWhen>
+      </handler>
    </extension>
    <extension
          point="org.eclipse.ui.menus">
@@ -155,6 +171,14 @@
                   checkEnabled="true">
             </visibleWhen>
          </command>
+         <command
+               commandId="org.eclipse.cdt.lsp.clangd.editor.commands.command.getSignatureHelp"
+               label="Receive Signature Help"
+               style="push">
+            <visibleWhen
+                  checkEnabled="true">
+            </visibleWhen>
+         </command>
       </menuContribution>
    </extension>
 

bundles/org.eclipse.cdt.lsp.clangd/src/org/eclipse/cdt/lsp/internal/clangd/editor/handlers/ReceiveSignatureHelpCommandHandler.java

@@ -0,0 +1,93 @@
+package org.eclipse.cdt.lsp.internal.clangd.editor.handlers;
+
+import java.net.URI;
+import java.util.Optional;
+
+import org.eclipse.core.commands.AbstractHandler;
+import org.eclipse.core.commands.ExecutionEvent;
+import org.eclipse.core.commands.ExecutionException;
+import org.eclipse.core.runtime.Adapters;
+import org.eclipse.jface.text.BadLocationException;
+import org.eclipse.jface.text.IDocument;
+import org.eclipse.jface.text.ITextSelection;
+import org.eclipse.jface.viewers.ISelection;
+import org.eclipse.lsp4e.LSPEclipseUtils;
+import org.eclipse.lsp4e.LanguageServers;
+import org.eclipse.lsp4j.SignatureHelp;
+import org.eclipse.lsp4j.SignatureHelpParams;
+import org.eclipse.ui.IEditorInput;
+import org.eclipse.ui.IEditorPart;
+import org.eclipse.ui.IFileEditorInput;
+import org.eclipse.ui.IURIEditorInput;
+import org.eclipse.ui.handlers.HandlerUtil;
+import org.eclipse.ui.texteditor.ITextEditor;
+
+public class ReceiveSignatureHelpCommandHandler extends AbstractHandler {
+
+	@Override
+	public Object execute(ExecutionEvent event) throws ExecutionException {
+		return execute(HandlerUtil.getActiveEditor(event), HandlerUtil.getCurrentSelection(event));
+	}
+
+	@SuppressWarnings("restriction")
+	private Object execute(IEditorPart activeEditor, ISelection currentSelection) {
+		// Try to adapt to ITextEditor (e.g. to support editors embedded in
+		// MultiPageEditorParts), otherwise use activeEditor.
+		IEditorPart innerEditor = Optional.ofNullable((IEditorPart) Adapters.adapt(activeEditor, ITextEditor.class))
+				.orElse(activeEditor);
+
+		if (!(currentSelection instanceof ITextSelection)) {
+			return null;
+		}
+
+		ITextSelection textSelection = (ITextSelection) currentSelection;
+
+		getUri(innerEditor).ifPresent(fileUri -> {
+			IDocument document = LSPEclipseUtils.getDocument(innerEditor.getEditorInput());
+
+			SignatureHelpParams signatureHelpParams = new SignatureHelpParams();
+			try {
+				signatureHelpParams.setTextDocument(LSPEclipseUtils.toTextDocumentIdentifier(document));
+				signatureHelpParams.setPosition(LSPEclipseUtils.toPosition(textSelection.getOffset(), document));
+			} catch (BadLocationException e) {
+				// TODO handle this
+				e.printStackTrace();
+			}
+
+			try {
+				Optional<SignatureHelp> result = LanguageServers.forDocument(document)
+						.computeFirst(server -> server.getTextDocumentService().signatureHelp(signatureHelpParams))
+						.get();
+				if (result.isPresent()) {
+					// TODO return AST
+					System.out.println(result.get());
+				}
+			} catch (InterruptedException | java.util.concurrent.ExecutionException e) {
+				// TODO Auto-generated catch block
+				e.printStackTrace();
+			}
+		});
+
+		return null;
+	}
+
+	/**
+	 * Returns the URI of the given editor depending on the type of its
+	 * {@link IEditorPart#getEditorInput()}.
+	 *
+	 * @return the URI or an empty {@link Optional} if the URI couldn't be
+	 *         determined.
+	 */
+	private static Optional<URI> getUri(IEditorPart editor) {
+		IEditorInput editorInput = editor.getEditorInput();
+
+		if (editorInput instanceof IFileEditorInput) {
+			return Optional.of(((IFileEditorInput) editor.getEditorInput()).getFile().getLocationURI());
+		} else if (editorInput instanceof IURIEditorInput) {
+			return Optional.of(((IURIEditorInput) editorInput).getURI());
+		} else {
+			return Optional.empty();
+		}
+	}
+
+}