Fixed thread safety issues and enabled parallel requirement processing

serenity-model/src/main/java/net/thucydides/model/requirements/AggregateRequirementsService.java

@@ -1,33 +1,24 @@
 package net.thucydides.model.requirements;
 
-import net.serenitybdd.model.collect.NewList;
-import net.serenitybdd.model.di.ModelInfrastructure;
-import net.serenitybdd.model.environment.EnvironmentSpecificConfiguration;
-import net.thucydides.model.ThucydidesSystemProperty;
 import net.thucydides.model.domain.TestOutcome;
-import net.thucydides.model.environment.SystemEnvironmentVariables;
 import net.thucydides.model.requirements.model.Requirement;
-import net.thucydides.model.statistics.service.AnnotationBasedTagProvider;
-import net.thucydides.model.statistics.service.FeatureStoryTagProvider;
 import net.thucydides.model.util.EnvironmentVariables;
 import org.apache.commons.lang3.time.StopWatch;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import java.util.*;
-import java.util.stream.Collectors;
 
 public class AggregateRequirementsService extends BaseRequirementsService implements RequirementsService {
 
-    private List<RequirementsTagProvider> requirementsTagProviders;
+    private final List<RequirementsTagProvider> requirementsTagProviders;
 
     public AggregateRequirementsService(EnvironmentVariables environmentVariables,
                                         RequirementsTagProvider... tagProviders) {
         super(environmentVariables);
-        this.requirementsTagProviders = NewList.of(tagProviders);
+        this.requirementsTagProviders = List.of(tagProviders);
     }
 
-
     private static final Logger LOGGER = LoggerFactory.getLogger(AggregateRequirementsService.class);
 
     @Override
@@ -36,10 +27,9 @@ public List<Requirement> getRequirements() {
             StopWatch stopWatch = StopWatch.createStarted();
 
             requirements = getRequirementsTagProviders().stream()
-                    // todo: enable parallel processing
-//                    .parallel()
+                    .parallel()
                     .flatMap(RequirementsProvided::asStream)
-                    .collect(Collectors.toCollection(MergedRequirementList::new));
+                    .collect(RequirementsCollector.merging());
 
             stopWatch.split();
             LOGGER.debug("Requirements loaded in {}", stopWatch.formatSplitTime());

serenity-model/src/main/java/net/thucydides/model/requirements/MultiSourceRequirementsService.java

@@ -14,7 +14,6 @@
 import org.slf4j.LoggerFactory;
 
 import java.util.*;
-import java.util.stream.Collectors;
 
 public class MultiSourceRequirementsService extends BaseRequirementsService implements RequirementsService {
 
@@ -41,7 +40,7 @@ public List<Requirement> getRequirements() {
             requirements = getRequirementsTagProviders().stream()
                     .parallel()
                     .flatMap(RequirementsProvided::asStream)
-                    .collect(Collectors.toCollection(MergedRequirementList::new));
+                    .collect(RequirementsCollector.merging());
 
             stopWatch.split();
             LOGGER.debug("Requirements loaded in {}", stopWatch.formatSplitTime());

serenity-model/src/main/java/net/thucydides/model/requirements/RequirementsCollector.java

@@ -0,0 +1,25 @@
+package net.thucydides.model.requirements;
+
+import net.thucydides.model.requirements.model.Requirement;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.stream.Collector;
+import java.util.stream.Collectors;
+
+public class RequirementsCollector {
+
+    private static final Collector<Requirement, ?, List<Requirement>> INSTANCE =
+            Collectors.collectingAndThen(
+                    Collectors.toMap(
+                            req -> req, // Using the requirement itself as the key since we have no unique ID to rely on
+                            req -> req,
+                            Requirement::merge
+                    ),
+                    map -> new ArrayList<>(map.values())
+            );
+
+    public static Collector<Requirement, ?, List<Requirement>> merging() {
+        return INSTANCE;
+    }
+}

serenity-model/src/main/java/net/thucydides/model/requirements/RequirementsProvided.java

@@ -4,16 +4,16 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 import java.util.stream.Stream;
 
 public class RequirementsProvided {
 
     private static final Logger LOGGER = LoggerFactory.getLogger(RequirementsTagProvider.class);
 
-    private static final Iterable<Requirement> NO_REQUIREMENTS = new ArrayList<>();
-    private static final List<Requirement> EMPTY_REQUIREMENTS = new ArrayList<>();
+    private static final Iterable<Requirement> NO_REQUIREMENTS = Collections.emptyList();
+    private static final List<Requirement> EMPTY_REQUIREMENTS = Collections.emptyList();
 
     public static Iterable<Requirement> by(RequirementsTagProvider tagProvider) {
         try {

serenity-model/src/test/java/net/thucydides/model/requirements/RequirementAncestryTest.java

@@ -11,8 +11,8 @@
 class RequirementAncestryTest {
 
     /**
-     * Parent ID must be set to an empty string for the {@link MergedRequirementList}
-     * to correctly merge the requirements discovered by different tag providers.
+     * Parent ID must be set to an empty string for the {@link Requirement#merge}
+     * to correctly merge the requirements discovered by the different tag providers.
      */
     @Test
     void sets_the_parent_id_to_empty_string_when_parent_does_not_exist() {