Add a ClasspathContributor for API tools annotations

Currently it is quite cumbersome to use and discover the PDE own API
tools annotations and requires some kind of workarounds.

This adds a classpath contributor that makes the annotations available
like already done for ds and bundle annotations.

Fix #447

apitools/org.eclipse.pde.api.tools/plugin.xml

@@ -328,4 +328,10 @@
        </run>
     </application>
  </extension>
+ <extension
+       point="org.eclipse.pde.core.pluginClasspathContributors">
+    <contributor
+          class="org.eclipse.pde.api.tools.internal.ApiAnnotationsClasspathContributor">
+    </contributor>
+ </extension>
 </plugin>

apitools/org.eclipse.pde.api.tools/src/org/eclipse/pde/api/tools/internal/ApiAnnotationsClasspathContributor.java

@@ -0,0 +1,78 @@
+/*******************************************************************************
+ * Copyright (c) 2023 Christoph Läubrich and others.
+ *
+ * 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
+ *
+ * Contributors:
+ *     Christoph Läubrich - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.pde.api.tools.internal;
+
+import java.util.Collection;
+import java.util.Collections;
+import java.util.List;
+import java.util.Objects;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+import org.eclipse.core.resources.IResource;
+import org.eclipse.core.runtime.CoreException;
+import org.eclipse.jdt.core.IClasspathEntry;
+import org.eclipse.osgi.service.resolver.BundleDescription;
+import org.eclipse.pde.api.tools.internal.provisional.ApiPlugin;
+import org.eclipse.pde.core.IClasspathContributor;
+import org.eclipse.pde.core.plugin.IPluginModelBase;
+import org.eclipse.pde.core.plugin.PluginRegistry;
+import org.eclipse.pde.internal.core.ClasspathUtilCore;
+
+public class ApiAnnotationsClasspathContributor implements IClasspathContributor {
+
+	private static final Collection<String> API_TOOLS_ANNOTATIONS = List.of("org.eclipse.pde.api.tools.annotations"); //$NON-NLS-1$
+
+	@Override
+	public List<IClasspathEntry> getInitialEntries(BundleDescription project) {
+		IPluginModelBase model = PluginRegistry.findModel(project);
+		if (hasApiNature(model)) {
+			return ClasspathUtilCore.classpathEntries(annotations()).collect(Collectors.toList());
+		}
+		return Collections.emptyList();
+	}
+
+
+
+	private boolean hasApiNature(IPluginModelBase model) {
+		if (model != null) {
+			IResource resource = model.getUnderlyingResource();
+			if (resource != null) {
+				try {
+					return resource.getProject().hasNature(ApiPlugin.NATURE_ID);
+				} catch (CoreException e) {
+					// assume not compatible project then...
+				}
+			}
+		}
+		return false;
+	}
+
+
+
+	/**
+	 * @return s stream of all current available annotations in the current plugin
+	 *         registry
+	 */
+	public static Stream<IPluginModelBase> annotations() {
+		return API_TOOLS_ANNOTATIONS.stream().map(PluginRegistry::findModel).filter(Objects::nonNull)
+				.filter(IPluginModelBase::isEnabled);
+	}
+
+	@Override
+	public List<IClasspathEntry> getEntriesForDependency(BundleDescription project, BundleDescription addedDependency) {
+		return Collections.emptyList();
+	}
+
+}

ui/org.eclipse.pde.core/src/org/eclipse/pde/internal/core/ClasspathUtilCore.java

@@ -17,11 +17,16 @@
 
 import java.io.File;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Collection;
+import java.util.Objects;
+import java.util.stream.Stream;
 
 import org.eclipse.core.resources.IResource;
 import org.eclipse.core.runtime.CoreException;
 import org.eclipse.core.runtime.IPath;
+import org.eclipse.jdt.core.IAccessRule;
+import org.eclipse.jdt.core.IClasspathAttribute;
 import org.eclipse.jdt.core.IClasspathEntry;
 import org.eclipse.jdt.core.JavaCore;
 import org.eclipse.osgi.service.resolver.BundleDescription;
@@ -76,6 +81,28 @@ private static Collection<ClasspathLibrary> collectLibraryEntries(IPluginModelBa
 		return entries;
 	}
 
+	public static Stream<IClasspathEntry> classpathEntries(Stream<IPluginModelBase> models) {
+		return models.flatMap(model -> {
+			String location = model.getInstallLocation();
+			if (location == null) {
+				return Stream.empty();
+			}
+			boolean isJarShape = new File(location).isFile();
+			IPluginLibrary[] libraries = model.getPluginBase().getLibraries();
+			if (isJarShape || libraries.length == 0) {
+				return Stream.of(IPath.fromOSString(location));
+			}
+			return Arrays.stream(libraries).filter(library -> !IPluginLibrary.RESOURCE.equals(library.getType()))
+					.map(library -> {
+						String name = library.getName();
+						String expandedName = ClasspathUtilCore.expandLibraryName(name);
+						IPath path = ClasspathUtilCore.getPath(model, expandedName, isJarShape);
+						return path;
+					}).filter(Objects::nonNull);
+		}).map(path -> JavaCore.newLibraryEntry(path, path, IPath.ROOT, new IAccessRule[0], new IClasspathAttribute[0],
+				false));
+	}
+
 	private static void addLibraryEntry(IPluginLibrary library, Collection<ClasspathLibrary> entries) {
 
 		String name = library.getName();

ui/org.eclipse.pde.core/src/org/eclipse/pde/internal/core/annotations/OSGiAnnotationsClasspathContributor.java

@@ -20,15 +20,12 @@
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
-import org.eclipse.core.runtime.IPath;
-import org.eclipse.jdt.core.IAccessRule;
-import org.eclipse.jdt.core.IClasspathAttribute;
 import org.eclipse.jdt.core.IClasspathEntry;
-import org.eclipse.jdt.core.JavaCore;
 import org.eclipse.osgi.service.resolver.BundleDescription;
 import org.eclipse.pde.core.IClasspathContributor;
 import org.eclipse.pde.core.plugin.IPluginModelBase;
 import org.eclipse.pde.core.plugin.PluginRegistry;
+import org.eclipse.pde.internal.core.ClasspathUtilCore;
 
 /**
  * This makes the <a href=
@@ -48,20 +45,14 @@ public class OSGiAnnotationsClasspathContributor implements IClasspathContributo
 	public List<IClasspathEntry> getInitialEntries(BundleDescription project) {
 		IPluginModelBase model = PluginRegistry.findModel(project);
 		if (model != null) {
-			return entries().collect(Collectors.toList());
+			return ClasspathUtilCore.classpathEntries(annotations()).collect(Collectors.toList());
 		}
 		return Collections.emptyList();
 	}
 
-	static Stream<IClasspathEntry> entries() {
-		return annotations().map(IPluginModelBase::getInstallLocation).filter(Objects::nonNull).map(IPath::fromOSString)
-				.map(path -> JavaCore.newLibraryEntry(path, path, IPath.ROOT, new IAccessRule[0],
-						new IClasspathAttribute[0], false));
-	}
-
 	/**
-	 * @return s stream of all current aviable annotations in the current plugin
-	 *         registry
+	 * @return s stream of all current available annotations in the current
+	 *         plugin registry
 	 */
 	public static Stream<IPluginModelBase> annotations() {
 		return OSGI_ANNOTATIONS.stream().map(PluginRegistry::findModel).filter(Objects::nonNull)