408511: [api] provide an extension to dynamically contribute connectors

Change-Id: If0acbbd24a543d13414ed4bf862a145803b6121c
Task-Url: https://bugs.eclipse.org/bugs/show_bug.cgi?id=408511

6 files changed, 244 insertions, 21 deletions

diff --git a/org.eclipse.mylyn.tasks.core/META-INF/MANIFEST.MF b/org.eclipse.mylyn.tasks.core/META-INF/MANIFEST.MF
index 6c8d85a3c..59f8a8698 100644
--- a/org.eclipse.mylyn.tasks.core/META-INF/MANIFEST.MF
+++ b/org.eclipse.mylyn.tasks.core/META-INF/MANIFEST.MF
@@ -25,5 +25,6 @@ Export-Package: org.eclipse.mylyn.internal.provisional.tasks.core;x-internal:=tr
  org.eclipse.mylyn.tasks.core.activity,
  org.eclipse.mylyn.tasks.core.context,
  org.eclipse.mylyn.tasks.core.data,
+ org.eclipse.mylyn.tasks.core.spi,
  org.eclipse.mylyn.tasks.core.sync
 Bundle-Localization: plugin
diff --git a/org.eclipse.mylyn.tasks.core/plugin.xml b/org.eclipse.mylyn.tasks.core/plugin.xml
index 219b5e723..cb398f106 100644
--- a/org.eclipse.mylyn.tasks.core/plugin.xml
+++ b/org.eclipse.mylyn.tasks.core/plugin.xml
@@ -17,4 +17,5 @@
    <extension-point id="taskActivationListeners" name="Task Activation Listeners" schema="schema/taskActivationListeners.exsd"/>
    <extension-point id="activityMonitor" name="Task Activity Monitor" schema="schema/activityMonitor.exsd"/>
    <extension-point id="contextStore" name="Task Context Store" schema="schema/contextStore.exsd"/>
+   <extension-point id="repositoryConnectorContributor" name="Repository Connector Contributor" schema="schema/repositoryConnectorContributor.exsd"/>
 </plugin>
diff --git a/org.eclipse.mylyn.tasks.core/schema/repositoryConnectorContributor.exsd b/org.eclipse.mylyn.tasks.core/schema/repositoryConnectorContributor.exsd
new file mode 100644
index 000000000..1009f3f5e
--- /dev/null
+++ b/org.eclipse.mylyn.tasks.core/schema/repositoryConnectorContributor.exsd
@@ -0,0 +1,102 @@
+<?xml version='1.0' encoding='UTF-8'?>
+<!-- Schema file written by PDE -->
+<schema targetNamespace="org.eclipse.mylyn.tasks.core" xmlns="http://www.w3.org/2001/XMLSchema">
+<annotation>
+      <appInfo>
+         <meta.schema plugin="org.eclipse.mylyn.tasks.core" id="repositoryConnectorContributor" name="Repository Connector Contributor"/>
+      </appInfo>
+      <documentation>
+         An extension point for contributing repository connector instances at runtime.
+      </documentation>
+   </annotation>
+
+   <element name="extension">
+      <annotation>
+         <appInfo>
+            <meta.element />
+         </appInfo>
+      </annotation>
+      <complexType>
+         <choice>
+            <element ref="contributor"/>
+         </choice>
+         <attribute name="point" type="string" use="required">
+            <annotation>
+               <documentation>
+                  
+               </documentation>
+            </annotation>
+         </attribute>
+         <attribute name="id" type="string">
+            <annotation>
+               <documentation>
+                  
+               </documentation>
+            </annotation>
+         </attribute>
+         <attribute name="name" type="string">
+            <annotation>
+               <documentation>
+                  
+               </documentation>
+               <appInfo>
+                  <meta.attribute translatable="true"/>
+               </appInfo>
+            </annotation>
+         </attribute>
+      </complexType>
+   </element>
+
+   <element name="contributor">
+      <complexType>
+         <attribute name="class" type="string">
+            <annotation>
+               <documentation>
+                  The class that contributes connector descriptors.
+               </documentation>
+               <appInfo>
+                  <meta.attribute kind="java" basedOn="org.eclipse.mylyn.tasks.core.RepositoryConnectorDescriptor:"/>
+               </appInfo>
+            </annotation>
+         </attribute>
+      </complexType>
+   </element>
+
+   <annotation>
+      <appInfo>
+         <meta.section type="since"/>
+      </appInfo>
+      <documentation>
+         3.10
+      </documentation>
+   </annotation>
+
+   <annotation>
+      <appInfo>
+         <meta.section type="examples"/>
+      </appInfo>
+      <documentation>
+         [Enter extension point usage example here.]
+      </documentation>
+   </annotation>
+
+   <annotation>
+      <appInfo>
+         <meta.section type="apiinfo"/>
+      </appInfo>
+      <documentation>
+         [Enter API information here.]
+      </documentation>
+   </annotation>
+
+   <annotation>
+      <appInfo>
+         <meta.section type="implementation"/>
+      </appInfo>
+      <documentation>
+         [Enter information about supplied implementation of this extension point.]
+      </documentation>
+   </annotation>
+
+
+</schema>
diff --git a/org.eclipse.mylyn.tasks.core/src/org/eclipse/mylyn/internal/tasks/core/util/RepositoryConnectorExtensionReader.java b/org.eclipse.mylyn.tasks.core/src/org/eclipse/mylyn/internal/tasks/core/util/RepositoryConnectorExtensionReader.java
index d4103c7ec..2137fbf98 100644
--- a/org.eclipse.mylyn.tasks.core/src/org/eclipse/mylyn/internal/tasks/core/util/RepositoryConnectorExtensionReader.java
+++ b/org.eclipse.mylyn.tasks.core/src/org/eclipse/mylyn/internal/tasks/core/util/RepositoryConnectorExtensionReader.java
@@ -12,6 +12,7 @@
 package org.eclipse.mylyn.internal.tasks.core.util;
 
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.HashSet;
 import java.util.LinkedHashMap;
 import java.util.List;
@@ -23,8 +24,11 @@ import org.eclipse.core.runtime.CoreException;
 import org.eclipse.core.runtime.IConfigurationElement;
 import org.eclipse.core.runtime.IExtension;
 import org.eclipse.core.runtime.IExtensionPoint;
+import org.eclipse.core.runtime.ISafeRunnable;
 import org.eclipse.core.runtime.IStatus;
 import org.eclipse.core.runtime.MultiStatus;
+import org.eclipse.core.runtime.Platform;
+import org.eclipse.core.runtime.SafeRunner;
 import org.eclipse.core.runtime.Status;
 import org.eclipse.mylyn.commons.core.StatusHandler;
 import org.eclipse.mylyn.internal.tasks.core.ITasksCoreConstants;
@@ -33,7 +37,8 @@ import org.eclipse.mylyn.internal.tasks.core.externalization.TaskListExternalize
 import org.eclipse.mylyn.tasks.core.AbstractRepositoryConnector;
 import org.eclipse.mylyn.tasks.core.AbstractRepositoryMigrator;
 import org.eclipse.mylyn.tasks.core.AbstractTaskListMigrator;
-import org.eclipse.mylyn.tasks.core.RepositoryConnectorDescriptor;
+import org.eclipse.mylyn.tasks.core.spi.RepositoryConnectorContributor;
+import org.eclipse.mylyn.tasks.core.spi.RepositoryConnectorDescriptor;
 import org.eclipse.osgi.util.NLS;
 
 public class RepositoryConnectorExtensionReader {
@@ -48,6 +53,9 @@ public class RepositoryConnectorExtensionReader {
 
 	public static final String ATTR_CLASS = "class"; //$NON-NLS-1$
 
+	private static final String EXTENSION_CONTRIBUTORS = ITasksCoreConstants.ID_PLUGIN
+			+ ".repositoryConnectorContributor"; //$NON-NLS-1$
+
 	private static class ConnectorFactory {
 
 		private AbstractRepositoryConnector connector;
@@ -61,6 +69,8 @@ public class RepositoryConnectorExtensionReader {
 		private final String pluginId;
 
 		public ConnectorFactory(RepositoryConnectorDescriptor descriptor, String pluginId) {
+			Assert.isNotNull(pluginId);
+			Assert.isNotNull(pluginId);
 			this.descriptor = descriptor;
 			this.pluginId = pluginId;
 		}
@@ -196,6 +206,10 @@ public class RepositoryConnectorExtensionReader {
 
 	private final TaskRepositoryManager repositoryManager;
 
+	private final List<ConnectorFactory> factories = new ArrayList<ConnectorFactory>();
+
+	private MultiStatus result;
+
 	public RepositoryConnectorExtensionReader(TaskListExternalizer taskListExternalizer,
 			TaskRepositoryManager repositoryManager) {
 		this.taskListExternalizer = taskListExternalizer;
@@ -203,28 +217,69 @@ public class RepositoryConnectorExtensionReader {
 	}
 
 	public void registerConnectors(IExtensionPoint repositoriesExtensionPoint) {
-		List<ConnectorFactory> descriptors = new ArrayList<ConnectorFactory>();
-		MultiStatus result = new MultiStatus(ITasksCoreConstants.ID_PLUGIN, 0,
-				"Repository connectors failed to load.", null); //$NON-NLS-1$
+		if (result != null) {
+			throw new IllegalStateException("registerConnectors may only be invoked once"); //$NON-NLS-1$
+		}
+
+		result = new MultiStatus(ITasksCoreConstants.ID_PLUGIN, 0, "Repository connectors failed to load.", null); //$NON-NLS-1$
+
+		Map<String, List<ConnectorFactory>> factoryById = readFromRepositoriesExtensionPoint(repositoriesExtensionPoint);
+		checkForConflicts(factoryById);
 
-		Map<String, List<ConnectorFactory>> factoryById = readFromRepositoriesExtensionPoint(
-				repositoriesExtensionPoint, descriptors);
-		checkForConflicts(descriptors, result, factoryById);
+		readFromContributorsExtensionPoint();
 
-		Map<String, List<ConnectorFactory>> factoryByConnectorKind = createConnectorInstances(descriptors, result);
-		checkForConflicts(descriptors, result, factoryByConnectorKind);
+		Map<String, List<ConnectorFactory>> factoryByConnectorKind = createConnectorInstances();
+		checkForConflicts(factoryByConnectorKind);
 
-		registerConnectorInstances(descriptors, result);
+		registerConnectorInstances();
 
 		if (!result.isOK()) {
 			StatusHandler.log(result);
 		}
 	}
 
-	public Map<String, List<ConnectorFactory>> createConnectorInstances(List<ConnectorFactory> descriptors,
-			MultiStatus result) {
+	private void readFromContributorsExtensionPoint() {
+		IExtensionPoint repositoriesExtensionPoint = Platform.getExtensionRegistry().getExtensionPoint(
+				EXTENSION_CONTRIBUTORS);
+		IExtension[] extensions = repositoriesExtensionPoint.getExtensions();
+		for (IExtension extension : extensions) {
+			IConfigurationElement[] elements = extension.getConfigurationElements();
+			for (IConfigurationElement element : elements) {
+				addDescriptorsFromContributor(element);
+			}
+		}
+	}
+
+	private void addDescriptorsFromContributor(final IConfigurationElement element) {
+		SafeRunner.run(new ISafeRunnable() {
+
+			@Override
+			public void run() throws Exception {
+				RepositoryConnectorContributor contributor = (RepositoryConnectorContributor) element.createExecutableExtension(ATTR_CLASS);
+				Collection<RepositoryConnectorDescriptor> descriptors = contributor.getDescriptors();
+				if (descriptors == null) {
+					result.add(new Status(IStatus.ERROR, ITasksCoreConstants.ID_PLUGIN, NLS.bind(
+							"Could not load connectors contributed by ''{0}''", element.getContributor().getName()))); //$NON-NLS-1$
+					return;
+				}
+				for (RepositoryConnectorDescriptor descriptor : descriptors) {
+					if (descriptor != null) {
+						factories.add(new ConnectorFactory(descriptor, element.getContributor().getName()));
+					}
+				}
+			}
+
+			@Override
+			public void handleException(Throwable exception) {
+				// ignore
+
+			}
+		});
+	}
+
+	public Map<String, List<ConnectorFactory>> createConnectorInstances() {
 		Map<String, List<ConnectorFactory>> factoryByConnectorKind = new LinkedHashMap<String, List<ConnectorFactory>>();
-		for (ConnectorFactory descriptor : descriptors) {
+		for (ConnectorFactory descriptor : factories) {
 			IStatus status = descriptor.createConnector();
 			if (status.isOK() && descriptor.getConnector() != null) {
 				add(factoryByConnectorKind, descriptor.getConnectorKind(), descriptor);
@@ -235,11 +290,11 @@ public class RepositoryConnectorExtensionReader {
 		return factoryByConnectorKind;
 	}
 
-	private void registerConnectorInstances(List<ConnectorFactory> descriptors, MultiStatus result) {
+	private void registerConnectorInstances() {
 		List<AbstractTaskListMigrator> taskListmigrators = new ArrayList<AbstractTaskListMigrator>();
 		List<AbstractRepositoryMigrator> repositoryMigrators = new ArrayList<AbstractRepositoryMigrator>();
 
-		for (ConnectorFactory descriptor : descriptors) {
+		for (ConnectorFactory descriptor : factories) {
 			if (descriptor.getConnector() != null) {
 				repositoryManager.addRepositoryConnector(descriptor.getConnector());
 
@@ -268,7 +323,7 @@ public class RepositoryConnectorExtensionReader {
 	}
 
 	private Map<String, List<ConnectorFactory>> readFromRepositoriesExtensionPoint(
-			IExtensionPoint repositoriesExtensionPoint, List<ConnectorFactory> descriptors) {
+			IExtensionPoint repositoriesExtensionPoint) {
 		// read core and migrator extensions to check for id conflicts
 		Map<String, List<ConnectorFactory>> factoryById = new LinkedHashMap<String, List<ConnectorFactory>>();
 
@@ -291,7 +346,7 @@ public class RepositoryConnectorExtensionReader {
 				descriptor.taskListMigratorElement = tasklistMigratorElement;
 				descriptor.repositoryMigratorElement = repositoryMigratorElement;
 				ConnectorFactory factory = new ConnectorFactory(descriptor, descriptor.getPluginId());
-				descriptors.add(factory);
+				factories.add(factory);
 				if (descriptor.getId() != null) {
 					add(factoryById, descriptor.getId(), factory);
 				}
@@ -300,8 +355,7 @@ public class RepositoryConnectorExtensionReader {
 		return factoryById;
 	}
 
-	private void checkForConflicts(List<ConnectorFactory> descriptors, MultiStatus result,
-			Map<String, List<ConnectorFactory>> descriptorById) {
+	private void checkForConflicts(Map<String, List<ConnectorFactory>> descriptorById) {
 		for (Map.Entry<String, List<ConnectorFactory>> entry : descriptorById.entrySet()) {
 			if (entry.getValue().size() > 1) {
 				MultiStatus status = new MultiStatus(ITasksCoreConstants.ID_PLUGIN, 0, NLS.bind(
@@ -310,7 +364,7 @@ public class RepositoryConnectorExtensionReader {
 					status.add(new Status(IStatus.ERROR, ITasksCoreConstants.ID_PLUGIN, NLS.bind(
 							"All extensions contributed by ''{0}'' have been disabled.", factory.getPluginId()), null)); //$NON-NLS-1$
 					disabledContributors.add(factory.getPluginId());
-					descriptors.remove(factory);
+					factories.remove(factory);
 				}
 				result.add(status);
 			}
@@ -330,4 +384,8 @@ public class RepositoryConnectorExtensionReader {
 		return new HashSet<String>(disabledContributors);
 	}
 
+	public IStatus getResult() {
+		return result;
+	}
+
 }
diff --git a/org.eclipse.mylyn.tasks.core/src/org/eclipse/mylyn/tasks/core/spi/RepositoryConnectorContributor.java b/org.eclipse.mylyn.tasks.core/src/org/eclipse/mylyn/tasks/core/spi/RepositoryConnectorContributor.java
new file mode 100644
index 000000000..de00d6f39
--- /dev/null
+++ b/org.eclipse.mylyn.tasks.core/src/org/eclipse/mylyn/tasks/core/spi/RepositoryConnectorContributor.java
@@ -0,0 +1,35 @@
+/*******************************************************************************
+ * Copyright (c) 2013 Tasktop Technologies and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *     Tasktop Technologies - initial API and implementation
+ *******************************************************************************/
+
+package org.eclipse.mylyn.tasks.core.spi;
+
+import java.util.List;
+
+import org.eclipse.jdt.annotation.NonNull;
+import org.eclipse.mylyn.tasks.core.AbstractRepositoryConnector;
+
+/**
+ * Implementors of this class can contribute instances of {@link AbstractRepositoryConnector} at runtime.
+ * 
+ * @since 3.10
+ */
+public abstract class RepositoryConnectorContributor {
+
+	/**
+	 * Returns a list of descriptors for connectors that are to be contributed. This method is invoked when the tasks
+	 * core framework is initialized.
+	 * 
+	 * @return a list of descriptors
+	 */
+	@NonNull
+	public abstract List<RepositoryConnectorDescriptor> getDescriptors();
+
+}
diff --git a/org.eclipse.mylyn.tasks.core/src/org/eclipse/mylyn/tasks/core/RepositoryConnectorDescriptor.java b/org.eclipse.mylyn.tasks.core/src/org/eclipse/mylyn/tasks/core/spi/RepositoryConnectorDescriptor.java
index f987dacf2..a0151d122 100644
--- a/org.eclipse.mylyn.tasks.core/src/org/eclipse/mylyn/tasks/core/RepositoryConnectorDescriptor.java
+++ b/org.eclipse.mylyn.tasks.core/src/org/eclipse/mylyn/tasks/core/spi/RepositoryConnectorDescriptor.java
@@ -9,17 +9,43 @@
  *     Tasktop Technologies - initial API and implementation
  *******************************************************************************/
 
-package org.eclipse.mylyn.tasks.core;
+package org.eclipse.mylyn.tasks.core.spi;
+
+import org.eclipse.jdt.annotation.NonNull;
+import org.eclipse.jdt.annotation.Nullable;
+import org.eclipse.mylyn.tasks.core.AbstractRepositoryConnector;
+import org.eclipse.mylyn.tasks.core.AbstractRepositoryMigrator;
+import org.eclipse.mylyn.tasks.core.AbstractTaskListMigrator;
 
 /**
+ * A descriptor for an {@link AbstractRepositoryConnector} instance.
+ * 
  * @since 3.10
  */
 public abstract class RepositoryConnectorDescriptor {
 
+	/**
+	 * Creates and returns a connector instance. Only invoked once.
+	 * 
+	 * @return a connector instance
+	 */
+	@NonNull
 	public abstract AbstractRepositoryConnector createRepositoryConnector();
 
+	/**
+	 * Creates and returns a task list migrator instance. Only invoked once.
+	 * 
+	 * @return a migrator or null if no migrator is provided
+	 */
+	@Nullable
 	public abstract AbstractTaskListMigrator createTaskListMigrator();
 
+	/**
+	 * Creates and returns a repository migrator instance. Only invoked once.
+	 * 
+	 * @return a migrator or null if no migrator is provided
+	 */
+	@Nullable
 	public abstract AbstractRepositoryMigrator createRepositoryMigrator();
 
 }