fix: advertise callHierarchy client capability

org.eclipse.lsp4e.test/src/org/eclipse/lsp4e/test/callhierarchy/CallHierarchyViewContentTest.java

@@ -0,0 +1,103 @@
+/*******************************************************************************
+ * Copyright (c) 2025 Vegard IT 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:
+ *  Sebastian Thomschke (Vegard IT GmbH) - initial implementation
+ *******************************************************************************/
+package org.eclipse.lsp4e.test.callhierarchy;
+
+import static org.eclipse.lsp4e.test.utils.TestUtils.waitForAndAssertCondition;
+import static org.junit.Assert.*;
+
+import org.eclipse.core.resources.IFile;
+import org.eclipse.core.resources.IProject;
+import org.eclipse.jface.text.IDocument;
+import org.eclipse.jface.viewers.DelegatingStyledCellLabelProvider;
+import org.eclipse.jface.viewers.TreeViewer;
+import org.eclipse.lsp4e.LSPEclipseUtils;
+import org.eclipse.lsp4e.callhierarchy.CallHierarchyContentProvider;
+import org.eclipse.lsp4e.callhierarchy.CallHierarchyLabelProvider;
+import org.eclipse.lsp4e.callhierarchy.CallHierarchyViewTreeNode;
+import org.eclipse.lsp4e.test.utils.AbstractTestWithProject;
+import org.eclipse.lsp4e.test.utils.TestUtils;
+import org.eclipse.lsp4e.tests.mock.MockLanguageServer;
+import org.eclipse.lsp4e.ui.views.HierarchyViewInput;
+import org.eclipse.lsp4j.ServerCapabilities;
+import org.eclipse.swt.layout.FillLayout;
+import org.eclipse.swt.widgets.Shell;
+import org.eclipse.swt.widgets.Tree;
+import org.eclipse.swt.widgets.TreeItem;
+import org.junit.Test;
+
+/**
+ * UI-level test that opens a file, initializes Call Hierarchy and verifies that
+ * the view model contains expected nodes. Uses the mock LS.
+ */
+public class CallHierarchyViewContentTest extends AbstractTestWithProject {
+
+	@Override
+	public void setUpProject() throws Exception {
+		super.setUpProject();
+		// Ensure the mock server advertises callHierarchyProvider
+		MockLanguageServer.reset(() -> {
+			ServerCapabilities caps = MockLanguageServer.defaultServerCapabilities();
+			caps.setCallHierarchyProvider(Boolean.TRUE);
+			return caps;
+		});
+	}
+
+	@Test
+	public void testCallHierarchyShowsCalleeAndCaller() throws Exception {
+		IProject p = project;
+		IFile file = TestUtils.createUniqueTestFile(p, "// mock content for call hierarchy\nfunction f(){}\n");
+
+		// Open the file in Generic Editor to bind the LS
+		var editor = TestUtils.openEditor(file);
+		IDocument document = LSPEclipseUtils.getDocument(editor.getEditorInput());
+		assertTrue(document != null);
+
+		// Create a lightweight view embedding a TreeViewer with the real content
+		// provider
+		Shell shell = new Shell(editor.getSite().getShell());
+		shell.setLayout(new FillLayout());
+		TreeViewer viewer = new TreeViewer(shell);
+		viewer.setContentProvider(new CallHierarchyContentProvider());
+		viewer.setLabelProvider(new DelegatingStyledCellLabelProvider(new CallHierarchyLabelProvider()));
+		shell.open();
+
+		// Initialize input similar to CallHierarchyView.initialize
+		viewer.setInput(new HierarchyViewInput(document, 0));
+
+		// Wait until the placeholder ("Finding callers ...") is replaced by a node
+		waitForAndAssertCondition(5_000, shell.getDisplay(), () -> {
+			Tree tree = viewer.getTree();
+			if (tree.getItemCount() == 0) return false;
+			Object data = tree.getItem(0).getData();
+			return data instanceof CallHierarchyViewTreeNode;
+		});
+
+		Tree tree = viewer.getTree();
+		TreeItem root = tree.getItem(0);
+		Object rootData = root.getData();
+		assertTrue("Expected CallHierarchyViewTreeNode root", rootData instanceof CallHierarchyViewTreeNode);
+		var rootNode = (CallHierarchyViewTreeNode) rootData;
+		assertEquals("callee", rootNode.getCallContainer().getName());
+
+		// Expand and wait for children
+		viewer.expandToLevel(2);
+		waitForAndAssertCondition(5_000, shell.getDisplay(), () -> {
+			return root.getItemCount() > 0 && root.getItem(0).getData() instanceof CallHierarchyViewTreeNode;
+		});
+		Object childData = root.getItem(0).getData();
+		assertTrue(childData instanceof CallHierarchyViewTreeNode);
+		var childNode = (CallHierarchyViewTreeNode) childData;
+		assertEquals("caller", childNode.getCallContainer().getName());
+
+		shell.close();
+	}
+}

org.eclipse.lsp4e.tests.mock/src/org/eclipse/lsp4e/tests/mock/MockLanguageServer.java

@@ -192,6 +192,15 @@ public static ServerCapabilities defaultServerCapabilities() {
 
 	@Override
 	public CompletableFuture<InitializeResult> initialize(InitializeParams params) {
+
+		// Gate callHierarchyProvider on client capability (like real servers do)
+		var caps = params != null ? params.getCapabilities() : null;
+		var textDocCaps = caps != null ? caps.getTextDocument() : null;
+		boolean clientSupportsCallHierarchy = textDocCaps != null && textDocCaps.getCallHierarchy() != null;
+		if (!clientSupportsCallHierarchy) {
+			initializeResult.getCapabilities().setCallHierarchyProvider(Either.forLeft(false));
+		}
+
 		return buildMaybeDelayedFuture(initializeResult);
 	}
 

org.eclipse.lsp4e.tests.mock/src/org/eclipse/lsp4e/tests/mock/MockTextDocumentService.java

@@ -29,6 +29,12 @@
 import java.util.stream.Collectors;
 
 import org.eclipse.lsp4j.CodeAction;
+import org.eclipse.lsp4j.CallHierarchyIncomingCall;
+import org.eclipse.lsp4j.CallHierarchyIncomingCallsParams;
+import org.eclipse.lsp4j.CallHierarchyItem;
+import org.eclipse.lsp4j.CallHierarchyOutgoingCall;
+import org.eclipse.lsp4j.CallHierarchyOutgoingCallsParams;
+import org.eclipse.lsp4j.CallHierarchyPrepareParams;
 import org.eclipse.lsp4j.CodeActionParams;
 import org.eclipse.lsp4j.CodeLens;
 import org.eclipse.lsp4j.CodeLensParams;
@@ -462,6 +468,43 @@ public CompletableFuture<SemanticTokens> semanticTokensFull(SemanticTokensParams
 
 	private static final Range DUMMY_RANGE = new Range(new Position(0, 0), new Position(0, 0));
 
+	// --------------------------------------
+	// Call Hierarchy (minimal mock support)
+	// --------------------------------------
+	@Override
+	public CompletableFuture<List<CallHierarchyItem>> prepareCallHierarchy(CallHierarchyPrepareParams params) {
+		final String uri = params.getTextDocument().getUri();
+		CallHierarchyItem callee = new CallHierarchyItem();
+		callee.setName("callee");
+		callee.setKind(SymbolKind.Function);
+		callee.setUri(uri);
+		callee.setRange(DUMMY_RANGE);
+		callee.setSelectionRange(DUMMY_RANGE);
+		return CompletableFuture.completedFuture(List.of(callee));
+	}
+
+	@Override
+	public CompletableFuture<List<CallHierarchyIncomingCall>> callHierarchyIncomingCalls(
+			CallHierarchyIncomingCallsParams params) {
+		CallHierarchyItem caller = new CallHierarchyItem();
+		caller.setName("caller");
+		caller.setKind(SymbolKind.Function);
+		caller.setUri(params.getItem().getUri());
+		caller.setRange(DUMMY_RANGE);
+		caller.setSelectionRange(DUMMY_RANGE);
+		CallHierarchyIncomingCall incoming = new CallHierarchyIncomingCall();
+		incoming.setFrom(caller);
+		incoming.setFromRanges(List.of(DUMMY_RANGE));
+		return CompletableFuture.completedFuture(List.of(incoming));
+	}
+
+	@Override
+	public CompletableFuture<List<CallHierarchyOutgoingCall>> callHierarchyOutgoingCalls(
+			CallHierarchyOutgoingCallsParams params) {
+		// No outgoing calls in the minimal mock
+		return CompletableFuture.completedFuture(List.of());
+	}
+
 	@Override
 	public CompletableFuture<List<TypeHierarchyItem>> prepareTypeHierarchy(TypeHierarchyPrepareParams params) {
 		return CompletableFuture.completedFuture(List.of(new TypeHierarchyItem("a", SymbolKind.Class,

org.eclipse.lsp4e/src/org/eclipse/lsp4e/internal/SupportedFeatures.java

@@ -14,6 +14,7 @@
 
 import java.util.List;
 
+import org.eclipse.lsp4j.CallHierarchyCapabilities;
 import org.eclipse.lsp4j.CodeActionCapabilities;
 import org.eclipse.lsp4j.CodeActionKind;
 import org.eclipse.lsp4j.CodeActionKindCapabilities;
@@ -67,6 +68,7 @@ public class SupportedFeatures {
 
 	public static TextDocumentClientCapabilities getTextDocumentClientCapabilities() {
 		final var textDocumentClientCapabilities = new TextDocumentClientCapabilities();
+		textDocumentClientCapabilities.setCallHierarchy(new CallHierarchyCapabilities());
 		final var codeAction = new CodeActionCapabilities(
 				new CodeActionLiteralSupportCapabilities(new CodeActionKindCapabilities(List.of( //
 						CodeActionKind.QuickFix, //