Improve message if artifact can not be downloaded from any repository

There are rare cases where one gets a message that an artifact can not
be downloaded from any repository, this has two pitfalls:

1) You don't get an idea what repositories are actually contacted
2) Its hard to find out who actually requires this artifact

This now enhances an IArtifactRequest by a method to set a "context iu"
why this artifact is requested. If the information is given, it searches
through the available IUs and gives additional information why it is
required and what repositories are queried.

bundles/org.eclipse.equinox.p2.engine/META-INF/MANIFEST.MF

@@ -2,7 +2,7 @@ Manifest-Version: 1.0
 Bundle-ManifestVersion: 2
 Bundle-Name: %pluginName
 Bundle-SymbolicName: org.eclipse.equinox.p2.engine;singleton:=true
-Bundle-Version: 2.10.100.qualifier
+Bundle-Version: 2.10.200.qualifier
 Bundle-Activator: org.eclipse.equinox.internal.p2.engine.EngineActivator
 Bundle-Vendor: %providerName
 Bundle-Localization: plugin

bundles/org.eclipse.equinox.p2.engine/src/org/eclipse/equinox/internal/p2/engine/DownloadManager.java

@@ -14,16 +14,20 @@
  *******************************************************************************/
 package org.eclipse.equinox.internal.p2.engine;
 
+import java.net.URI;
 import java.util.*;
+import java.util.stream.Collectors;
 import org.eclipse.core.runtime.*;
 import org.eclipse.equinox.internal.p2.engine.phases.Collect;
 import org.eclipse.equinox.internal.provisional.p2.core.eventbus.IProvisioningEventBus;
 import org.eclipse.equinox.p2.core.IProvisioningAgent;
 import org.eclipse.equinox.p2.engine.ProvisioningContext;
+import org.eclipse.equinox.p2.metadata.*;
 import org.eclipse.equinox.p2.metadata.expression.ExpressionUtil;
 import org.eclipse.equinox.p2.query.*;
 import org.eclipse.equinox.p2.repository.artifact.IArtifactRepository;
 import org.eclipse.equinox.p2.repository.artifact.IArtifactRequest;
+import org.eclipse.osgi.util.NLS;
 
 public class DownloadManager {
 	private ProvisioningContext provContext = null;
@@ -49,9 +53,15 @@ public int compare(IArtifactRepository arg0, IArtifactRepository arg1) {
 			return 0;
 		}
 	};
+	private Set<IInstallableUnit> ius;
 
 	public DownloadManager(ProvisioningContext context, IProvisioningAgent agent) {
+		this(context, Set.of(), agent);
+	}
+
+	public DownloadManager(ProvisioningContext context, Set<IInstallableUnit> ius, IProvisioningAgent agent) {
 		provContext = context;
+		this.ius = ius;
 		this.agent = agent;
 	}
 
@@ -96,7 +106,7 @@ public IStatus start(IProgressMonitor monitor) {
 			if (repositories.length == 0)
 				return new Status(IStatus.ERROR, EngineActivator.ID, Messages.download_no_repository, new Exception(Collect.NO_ARTIFACT_REPOSITORIES_AVAILABLE));
 			fetch(repositories, subMonitor.newChild(500));
-			return overallStatus(monitor);
+			return overallStatus(monitor, repositories);
 		} finally {
 			subMonitor.done();
 		}
@@ -148,12 +158,7 @@ private IArtifactRequest[] getRequestsForRepository(IArtifactRepository reposito
 		return applicable.toArray(new IArtifactRequest[applicable.size()]);
 	}
 
-	//	private void notifyFetched() {
-	//		ProvisioningEventBus bus = (ProvisioningEventBus) ServiceHelper.getService(DownloadActivator.context, ProvisioningEventBus.class);
-	//		bus.publishEvent();
-	//	}
-
-	private IStatus overallStatus(IProgressMonitor monitor) {
+	private IStatus overallStatus(IProgressMonitor monitor, IArtifactRepository[] repositories) {
 		if (monitor != null && monitor.isCanceled())
 			return Status.CANCEL_STATUS;
 
@@ -163,9 +168,51 @@ private IStatus overallStatus(IProgressMonitor monitor) {
 		MultiStatus result = new MultiStatus(EngineActivator.ID, IStatus.OK, null, null);
 		for (IArtifactRequest request : requestsToProcess) {
 			IStatus failed = request.getResult();
-			if (failed != null && !failed.isOK())
+			if (failed != null && !failed.isOK()) {
+				IArtifactKey key = request.getArtifactKey();
+				IInstallableUnit unit = getUnit(key);
+				if (unit != null) {
+					String dependencyPath = computeDependency(unit);
+					result.add(Status.error(NLS.bind(Messages.DownloadManager_cant_find_artifact,
+							new Object[] { request.getArtifactKey().toString(), dependencyPath,
+									Arrays.stream(repositories).map(repo -> repo.getLocation()).filter(Objects::nonNull)
+											.map(URI::toString).collect(Collectors.joining(System.lineSeparator(),
+													System.lineSeparator(), "")) }))); //$NON-NLS-1$
+					continue;
+				}
 				result.add(failed);
+			}
 		}
 		return result;
 	}
+
+	private IInstallableUnit getUnit(IArtifactKey artifactKey) {
+		if (ius != null) {
+			for (IInstallableUnit unit : ius) {
+				if (unit.getArtifacts().contains(artifactKey)) {
+					return unit;
+				}
+			}
+		}
+		return null;
+	}
+
+	private String computeDependency(IInstallableUnit unit) {
+		List<String> requiredBy = new ArrayList<>();
+		requiredBy.add(toIdAndVersion(unit));
+		if (ius != null) {
+			for (IInstallableUnit other : ius) {
+				List<IRequirement> requirement = other.getRequirements().stream().filter(req -> unit.satisfies(req))
+						.toList();
+				if (!requirement.isEmpty()) {
+					requiredBy.add(toIdAndVersion(other));
+				}
+			}
+		}
+		return requiredBy.stream().collect(Collectors.joining(", ")); //$NON-NLS-1$
+	}
+
+	private static String toIdAndVersion(IInstallableUnit unit) {
+		return String.format("%s[%s]", unit.getId(), unit.getVersion()); //$NON-NLS-1$
+	}
 }

bundles/org.eclipse.equinox.p2.engine/src/org/eclipse/equinox/internal/p2/engine/Messages.java

@@ -46,6 +46,8 @@ public class Messages extends NLS {
 	public static String committing;
 	public static String download_artifact;
 	public static String download_no_repository;
+
+	public static String DownloadManager_cant_find_artifact;
 	public static String Engine_Operation_Canceled_By_User;
 
 	public static String EngineActivator_0;

bundles/org.eclipse.equinox.p2.engine/src/org/eclipse/equinox/internal/p2/engine/messages.properties

@@ -108,6 +108,7 @@ CertificateChecker_SignedContentError=Error with signed content.
 CertificateChecker_SignedContentIOError=Error reading signed content.
 CertificateChecker_UnsignedNotAllowed=Installing unsigned artifacts is not permitted: {0}
 CertificateChecker_UnsignedRejected=Unsigned content is rejected. Installation cannot proceed.
+DownloadManager_cant_find_artifact=Can't download artifact {0} required by {1} from any of the following repositories: {2}
 
 Phase_Collect_Error=An error occurred while collecting items to be installed
 Phase_Configure_Error=An error occurred while configuring the installed items

bundles/org.eclipse.equinox.p2.engine/src/org/eclipse/equinox/internal/p2/engine/phases/Collect.java

@@ -89,9 +89,9 @@ protected IStatus completePhase(IProgressMonitor monitor, IProfile profile, Map<
 			agent = (IProvisioningAgent) parameters.get(PARM_AGENT);
 		}
 
+		@SuppressWarnings("unchecked")
+		Set<IInstallableUnit> ius = (Set<IInstallableUnit>) parameters.get(PARM_IUS);
 		if (Boolean.parseBoolean(context.getProperty(ProvisioningContext.CHECK_AUTHORITIES))) {
-			@SuppressWarnings("unchecked")
-			Set<IInstallableUnit> ius = (Set<IInstallableUnit>) parameters.get(PARM_IUS);
 			IStatus authorityStatus = new AuthorityChecker(agent, context, ius, artifactRequests.stream()
 						.flatMap(Arrays::stream).map(IArtifactRequest::getArtifactKey).collect(Collectors.toList()),
 						profile).start(monitor);
@@ -111,7 +111,7 @@ protected IStatus completePhase(IProgressMonitor monitor, IProfile profile, Map<
 		}
 
 		List<IArtifactRequest> totalArtifactRequests = new ArrayList<>(artifactRequests.size());
-		DownloadManager dm = new DownloadManager(context, agent);
+		DownloadManager dm = new DownloadManager(context, ius, agent);
 		for (IArtifactRequest[] requests : artifactRequests) {
 			for (IArtifactRequest request : requests) {
 				dm.add(request);