Fix API tools slow down with multiple source folders sharing output

The fix in commit 215a618 for issue #2096 introduced an O(n^2) time
complexity regression when projects have multiple source folders
sharing the same output location (like SWT with 26 source roots).

The problem was that each source folder caused a new CompositeApiTypeContainer
to be created, wrapping all previous containers plus a new one. This
resulted in exponential duplication of container visits during API analysis.

The fix modifies ProjectTypeContainer to support multiple
IPackageFragmentRoots, allowing a single container to discover packages
from all source folders that share the same output location. This avoids
creating composite containers and maintains O(n) complexity.

Fixes #2197

Signed-off-by: moaead <moaead@users.noreply.github.com>

Author: Moaead Yahya

apitools/org.eclipse.pde.api.tools.tests/src/org/eclipse/pde/api/tools/builder/tests/compatibility/ProjectTypeContainerTests.java

@@ -261,7 +261,9 @@ public void testMultipleSourceFoldersWithSharedOutput() throws CoreException {
 		IApiTypeContainer[] containers = component.getApiTypeContainers();
 		assertEquals("Wrong number of API type containers", 1, containers.length); //$NON-NLS-1$
 		IApiTypeContainer container = containers[0];
-		assertEquals("Should be a composite type container", IApiTypeContainer.COMPOSITE, //$NON-NLS-1$
+		// A single ProjectTypeContainer handles multiple source roots sharing
+		// the same output location by tracking all package fragment roots
+		assertEquals("Should be a folder type container", IApiTypeContainer.FOLDER, //$NON-NLS-1$
 				container.getContainerType());
 
 		String[] packageNames = container.getPackageNames();

apitools/org.eclipse.pde.api.tools/src/org/eclipse/pde/api/tools/internal/model/ProjectComponent.java

@@ -14,7 +14,6 @@
 package org.eclipse.pde.api.tools.internal.model;
 
 import java.util.ArrayList;
-import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
 import java.util.Map;
@@ -419,30 +418,11 @@ private static IApiTypeContainer getApiTypeContainer(String location, ProjectCom
 						}
 						cfc = new ProjectTypeContainer(component, container, root);
 						outputLocationToContainer.put(outputLocation, cfc);
-					} else {
+					} else if (cfc instanceof ProjectTypeContainer) {
 						// Multiple source folders share the same output location
-						// Create a composite container to include packages from all source roots
-						List<IApiTypeContainer> containers = new ArrayList<>();
-						if (cfc instanceof CompositeApiTypeContainer) {
-							// Already a composite, add to it
-							IApiTypeContainer[] typeContainers = ((CompositeApiTypeContainer) cfc)
-									.getApiTypeContainers();
-							containers.addAll(Arrays.asList(typeContainers));
-						} else {
-							// Convert single container to composite
-							containers.add(cfc);
-						}
-						// Add new container for this source root
-						IPath projectFullPath = project.getProject().getFullPath();
-						IContainer container = null;
-						if (projectFullPath.equals(outputLocation)) {
-							container = project.getProject();
-						} else {
-							container = project.getProject().getWorkspace().getRoot().getFolder(outputLocation);
-						}
-						containers.add(new ProjectTypeContainer(component, container, root));
-						cfc = new CompositeApiTypeContainer(component, containers);
-						outputLocationToContainer.put(outputLocation, cfc);
+						// Add the new package fragment root to the existing container
+						// so it can discover packages from all source roots
+						((ProjectTypeContainer) cfc).addPackageFragmentRoot(root);
 					}
 					return cfc;
 				}

apitools/org.eclipse.pde.api.tools/src/org/eclipse/pde/api/tools/internal/model/ProjectTypeContainer.java

@@ -15,10 +15,10 @@
 
 import java.util.ArrayList;
 import java.util.List;
-import java.util.Objects;
 import java.util.Set;
 import java.util.SortedSet;
 import java.util.TreeSet;
+import java.util.concurrent.CopyOnWriteArrayList;
 
 import org.eclipse.core.resources.IContainer;
 import org.eclipse.core.resources.IFile;
@@ -50,9 +50,10 @@ public class ProjectTypeContainer extends ApiElement implements IApiTypeContaine
 	private String[] fPackageNames;
 
 	/**
-	 * Optional package fragment root for JDT-based package discovery
+	 * Package fragment roots for JDT-based package discovery. Multiple roots
+	 * may exist when several source folders share the same output location.
 	 */
-	private final IPackageFragmentRoot fPackageFragmentRoot;
+	private final List<IPackageFragmentRoot> fPackageFragmentRoots = new CopyOnWriteArrayList<>();
 
 	/**
 	 * Constructs an {@link IApiTypeContainer} rooted at the location with an
@@ -67,7 +68,24 @@ public class ProjectTypeContainer extends ApiElement implements IApiTypeContaine
 	public ProjectTypeContainer(IApiElement parent, IContainer container, IPackageFragmentRoot packageFragmentRoot) {
 		super(parent, IApiElement.API_TYPE_CONTAINER, container.getName());
 		this.fRoot = container;
-		this.fPackageFragmentRoot = Objects.requireNonNull(packageFragmentRoot);
+		if (packageFragmentRoot != null) {
+			this.fPackageFragmentRoots.add(packageFragmentRoot);
+		}
+	}
+
+	/**
+	 * Adds an additional package fragment root to this container. This is used
+	 * when multiple source folders share the same output location.
+	 *
+	 * @param root the package fragment root to add
+	 * @since 1.3.400
+	 */
+	public void addPackageFragmentRoot(IPackageFragmentRoot root) {
+		if (root != null && !fPackageFragmentRoots.contains(root)) {
+			fPackageFragmentRoots.add(root);
+			// Clear cached package names so they will be recomputed
+			fPackageNames = null;
+		}
 	}
 
 	@Override
@@ -159,8 +177,10 @@ public IApiTypeRoot findTypeRoot(String qualifiedName) throws CoreException {
 	public String[] getPackageNames() throws CoreException {
 		if (fPackageNames == null) {
 			SortedSet<String> names = new TreeSet<>();
-			if (fPackageFragmentRoot.exists()) {
-				collectPackageNames(names, fPackageFragmentRoot);
+			for (IPackageFragmentRoot root : fPackageFragmentRoots) {
+				if (root.exists()) {
+					collectPackageNames(names, root);
+				}
 			}
 			fPackageNames = names.toArray(String[]::new);
 		}