Fix index out of bounds exception when using DMN Hit Policy Priority and no results

Fixes #4092

Author: filiphr

modules/flowable-dmn-engine/src/main/java/org/flowable/dmn/engine/impl/hitpolicy/HitPolicyPriority.java

@@ -73,6 +73,9 @@ public int compare(Object o1, Object o2) {
             }
         });
 
-        executionContext.getAuditContainer().addDecisionResultObject(ruleResults.get(0));
+        if (!ruleResults.isEmpty()) {
+            executionContext.getAuditContainer().addDecisionResultObject(ruleResults.get(0));
+        }
+
     }
 }

modules/flowable-dmn-engine/src/test/java/org/flowable/dmn/engine/test/runtime/HitPolicyCollectTest.java

@@ -44,6 +44,19 @@ public void collectHitPolicyNoAggregator() {
                 .containsExactly("OUTPUT1", "OUTPUT2", "OUTPUT3");
     }
 
+    @Test
+    @DmnDeployment(resources = "org/flowable/dmn/engine/test/runtime/HitPolicyCollectTest.collectHitPolicyNoAggregator.dmn")
+    public void collectHitPolicyNoAggregatorNoMatch() {
+        DmnDecisionService dmnRuleService = dmnEngine.getDmnDecisionService();
+
+        List<Map<String, Object>> result = dmnRuleService.createExecuteDecisionBuilder()
+                .decisionKey("decision1")
+                .variable("inputVariable1", 50)
+                .execute();
+
+        assertThat(result).isEmpty();
+    }
+
     @Test
     @DmnDeployment
     public void collectHitPolicyNoAggregatorCompound() {
@@ -110,6 +123,19 @@ public void collectHitPolicySUM() {
                 .containsExactly(entry("outputVariable1", 90D));
     }
 
+    @Test
+    @DmnDeployment(resources = "org/flowable/dmn/engine/test/runtime/HitPolicyCollectTest.collectHitPolicySUM.dmn")
+    public void collectHitPolicySUMNoMatch() {
+        DmnDecisionService dmnRuleService = dmnEngine.getDmnDecisionService();
+
+        Map<String, Object> result = dmnRuleService.createExecuteDecisionBuilder()
+                .decisionKey("decision1")
+                .variable("inputVariable1", 50)
+                .executeWithSingleResult();
+
+        assertThat(result).isNull();
+    }
+
     @Test
     @DmnDeployment
     public void collectHitPolicySUM_force_DMN11() {

modules/flowable-dmn-engine/src/test/java/org/flowable/dmn/engine/test/runtime/HitPolicyFirstTest.java

@@ -43,4 +43,17 @@ public void firstHitPolicy() {
                         entry("outputVariable2", "result2")
                 );
     }
+
+    @Test
+    @DmnDeployment
+    public void firstHitPolicyNoMatch() {
+        DmnDecisionService dmnRuleService = dmnEngine.getDmnDecisionService();
+
+        Map<String, Object> result = dmnRuleService.createExecuteDecisionBuilder()
+                .decisionKey("decision1")
+                .variable("inputVariable1", 50)
+                .executeWithSingleResult();
+
+        assertThat(result).isNull();
+    }
 }

modules/flowable-dmn-engine/src/test/java/org/flowable/dmn/engine/test/runtime/HitPolicyOutputOrderTest.java

@@ -44,6 +44,19 @@ public void outputOrderHitPolicy() {
                 .containsExactly("OUTPUT2", "OUTPUT3", "OUTPUT1");
     }
 
+    @Test
+    @DmnDeployment(resources = "org/flowable/dmn/engine/test/runtime/HitPolicyOutputOrderTest.outputOrderHitPolicy.dmn")
+    public void outputOrderHitPolicyNoMatch() {
+        DmnDecisionService dmnRuleService = dmnEngine.getDmnDecisionService();
+
+        List<Map<String, Object>> result = dmnRuleService.createExecuteDecisionBuilder()
+                .decisionKey("decision1")
+                .variable("inputVariable1", 50)
+                .execute();
+
+        assertThat(result).isEmpty();
+    }
+
     @Test
     @DmnDeployment
     public void outputOrderHitPolicyNumberAsString() {

modules/flowable-dmn-engine/src/test/java/org/flowable/dmn/engine/test/runtime/HitPolicyPriorityTest.java

@@ -42,6 +42,19 @@ public void priorityHitPolicy() {
                 .containsOnly(entry("outputVariable1", "OUTPUT2"));
     }
 
+    @Test
+    @DmnDeployment(resources = "org/flowable/dmn/engine/test/runtime/HitPolicyPriorityTest.priorityHitPolicy.dmn")
+    public void priorityHitPolicyNoMatch() {
+        DmnDecisionService dmnRuleService = dmnEngine.getDmnDecisionService();
+
+        Map<String, Object> result = dmnRuleService.createExecuteDecisionBuilder()
+                .decisionKey("decision1")
+                .variable("inputVariable1", 50)
+                .executeWithSingleResult();
+
+        assertThat(result).isNull();
+    }
+
     @Test
     @DmnDeployment
     public void priorityHitPolicyCompound() {

modules/flowable-dmn-engine/src/test/resources/org/flowable/dmn/engine/test/runtime/HitPolicyFirstTest.firstHitPolicyNoMatch.dmn

@@ -0,0 +1,35 @@
+<definitions xmlns="http://www.omg.org/spec/DMN/20151101" id="full" name="Full" namespace="http://www.flowable.org/dmn">
+  <decision id="decision1" name="Full Decision">
+    <decisionTable id="decisionTable" hitPolicy="FIRST">
+      <input>
+        <inputExpression id="inputVariable1" typeRef="double">
+          <text>inputVariable1</text>
+        </inputExpression>
+      </input>
+      <output id="output1" label="Output 1" name="outputVariable1" typeRef="string"></output>
+      <output id="output2" label="Output 2" name="outputVariable2" typeRef="string"></output>
+      <rule>
+        <inputEntry id="inputEntry1">
+          <text><![CDATA[< 10]]></text>
+        </inputEntry>
+        <outputEntry id="outputEntry1_1">
+          <text>'lt 10'</text>
+        </outputEntry>
+        <outputEntry id="outputEntry1_2">
+          <text>'result1'</text>
+        </outputEntry>
+      </rule>
+      <rule>
+        <inputEntry id="inputEntry3">
+          <text><![CDATA[< 20]]></text>
+        </inputEntry>
+        <outputEntry id="outputEntry3_1">
+          <text>'lt 20'</text>
+        </outputEntry>
+        <outputEntry id="outputEntry3_2">
+          <text>'result3'</text>
+        </outputEntry>
+      </rule>
+    </decisionTable>
+  </decision>
+</definitions>