order and deuplicate build issues

pitest-entry/src/main/java/org/pitest/mutationtest/ListenerArguments.java

@@ -10,6 +10,7 @@
 import java.util.Collections;
 import java.util.List;
 import java.util.Optional;
+import java.util.stream.Collectors;
 
 /**
  * Data passed to the listener MutationResultListener factories for use when
@@ -55,7 +56,10 @@ public ListenerArguments(ResultOutputStrategy outputStrategy,
     this.fullMutationMatrix = fullMutationMatrix;
     this.data = data;
     this.setting = setting;
-    this.issues = issues;
+    this.issues = issues.stream()
+            .distinct()
+            .sorted()
+            .collect(Collectors.toList());
   }
 
   public ResultOutputStrategy getOutputStrategy() {

pitest-entry/src/test/java/org/pitest/mutationtest/ListenerArgumentsTest.java

@@ -0,0 +1,29 @@
+package org.pitest.mutationtest;
+
+import org.junit.Test;
+import org.pitest.mutationtest.verify.BuildIssue;
+
+import java.util.List;
+
+import static java.util.Arrays.asList;
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class ListenerArgumentsTest {
+
+    @Test
+    public void removesDuplicateBuildIssues() {
+        List<BuildIssue> issues = asList(BuildIssue.issue("foo"), BuildIssue.issue("foo"));
+        ListenerArguments underTest = new ListenerArguments(null, null, null, null, 0, false, null, issues);
+        assertThat(underTest.issues()).containsExactly(BuildIssue.issue("foo"));
+    }
+
+    @Test
+    public void ordersBuildIssuesByPriority() {
+        BuildIssue a = new BuildIssue("foo", null, 5);
+        BuildIssue b = new BuildIssue("important", null, 0);
+        BuildIssue c = new BuildIssue("bar", null, 4);
+        List<BuildIssue> issues = asList(a,b,c);
+        ListenerArguments underTest = new ListenerArguments(null, null, null, null, 0, false, null, issues);
+        assertThat(underTest.issues()).containsExactly(b, c, a);
+    }
+}

pitest-html-report/src/main/java/org/pitest/mutationtest/report/html/MutationHtmlReportListener.java

@@ -238,6 +238,7 @@ private void createIndexPages() {
 
   private List<ConvertedIssue> wrap(List<BuildIssue> issues) {
     return issues.stream()
+            .distinct()
             .sorted()
             .map(ConvertedIssue::new)
             .collect(Collectors.toList());