PluginService: add a method to sort plugins

If you have a list of instances, but not their PluginInfo metadata
anymore, the priority will not be known unless the plugin type extends
HasPluginInfo. But regardless, we can look up the infos again, match
the instances against the looked-up infos, and sort that way.

Author: ctrueden

pom.xml

@@ -10,7 +10,7 @@
 	</parent>
 
 	<artifactId>scijava-common</artifactId>
-	<version>2.68.1-SNAPSHOT</version>
+	<version>2.69.0-SNAPSHOT</version>
 
 	<name>SciJava Common</name>
 	<description>SciJava Common is a shared library for SciJava software. It provides a plugin framework, with an extensible mechanism for service discovery, backed by its own annotation processor, so that plugins can be loaded dynamically. It is used by downstream projects in the SciJava ecosystem, such as ImageJ and SCIFIO.</description>

src/main/java/org/scijava/plugin/PluginService.java

@@ -34,8 +34,14 @@
 
 
 import java.util.Collection;
+import java.util.Collections;
+import java.util.Comparator;
 import java.util.List;
+import java.util.Map;
+import java.util.function.Function;
+import java.util.stream.Collectors;
 
+import org.scijava.Priority;
 import org.scijava.service.SciJavaService;
 
 /**
@@ -254,4 +260,23 @@ public interface PluginService extends SciJavaService {
 	 */
 	<PT extends SciJavaPlugin> PT createInstance(PluginInfo<PT> info);
 
+	/**
+	 * Sorts the given list of plugin instances by priority.
+	 * 
+	 * @param instances List of plugin instances to sort.
+	 * @param type The type of plugin these instances represent.
+	 */
+	default <PT extends SciJavaPlugin> void sort(final List<PT> instances,
+		final Class<PT> type)
+	{
+		// Create a mapping from plugin classes to priorities.
+		final List<PluginInfo<PT>> plugins = getPluginsOfType(type);
+		final Map<Class<?>, PluginInfo<PT>> infos = plugins.stream().collect(//
+			Collectors.toMap(PluginInfo::getPluginClass, Function.identity()));
+
+		// Compare plugin instances by priority via the mapping.
+		final Comparator<PT> comparator = (o1, o2) -> Priority.compare(//
+			infos.get(o1.getClass()), infos.get(o2.getClass()));
+		Collections.sort(instances, comparator);
+	}
 }