SONAR-6730 Measure computer should allowed no Input metrics

For instance, when a measure computer needs only issues to compute measures, it won't declare any input metrics

2 files changed, 37 insertions, 23 deletions

diff --git a/sonar-plugin-api/src/main/java/org/sonar/api/ce/measure/MeasureComputer.java b/sonar-plugin-api/src/main/java/org/sonar/api/ce/measure/MeasureComputer.java
index 32d5d90e469..d62851006a6 100644
--- a/sonar-plugin-api/src/main/java/org/sonar/api/ce/measure/MeasureComputer.java
+++ b/sonar-plugin-api/src/main/java/org/sonar/api/ce/measure/MeasureComputer.java
@@ -48,24 +48,29 @@ public interface MeasureComputer {
   interface MeasureComputerBuilder {
 
     /**
-     * @throws IllegalStateException if there's not at least one input metrics
-     */
+     * Input metrics can be empty (for instance when only issues are needed)
+     * @throws NullPointerException if inputMetrics is null
+     * @throws NullPointerException if the metrics contains a {@code null}
+     * */
     MeasureComputerBuilder setInputMetrics(String... inputMetrics);
 
     /**
-     * @throws IllegalStateException if there's not at least one output metrics
+     * @throws IllegalArgumentException if there's not at least one output metrics
+     * @throws NullPointerException if the metrics contains a {@code null}
      */
     MeasureComputerBuilder setOutputMetrics(String... outMetrics);
 
     /**
-     * @throws IllegalStateException if there's no implementation
+     * @throws NullPointerException if there's no implementation
      */
     MeasureComputerBuilder setImplementation(Implementation impl);
 
     /**
-     * @throws IllegalStateException if there's not at least one input metrics
-     * @throws IllegalStateException if there's not at least one output metrics
-     * @throws IllegalStateException if there's no implementation
+     * @throws NullPointerException if inputMetrics is null
+     * @throws NullPointerException if inputs metrics contains a {@code null}
+     * @throws IllegalArgumentException if there's not at least one output metrics
+     * @throws NullPointerException if outputs metrics contains a {@code null}
+     * @throws NullPointerException if there's no implementation
      */
     MeasureComputer build();
   }
diff --git a/sonar-plugin-api/src/test/java/org/sonar/api/test/ce/measure/MeasureComputerImpl.java b/sonar-plugin-api/src/test/java/org/sonar/api/test/ce/measure/MeasureComputerImpl.java
index 653499c6efe..b661247a517 100644
--- a/sonar-plugin-api/src/test/java/org/sonar/api/test/ce/measure/MeasureComputerImpl.java
+++ b/sonar-plugin-api/src/test/java/org/sonar/api/test/ce/measure/MeasureComputerImpl.java
@@ -22,9 +22,11 @@ package org.sonar.api.test.ce.measure;
 
 import com.google.common.collect.ImmutableSet;
 import java.util.Set;
+import javax.annotation.Nullable;
 import org.sonar.api.ce.measure.MeasureComputer;
 
 import static com.google.common.base.Preconditions.checkArgument;
+import static java.util.Objects.requireNonNull;
 
 public class MeasureComputerImpl implements MeasureComputer {
 
@@ -64,49 +66,56 @@ public class MeasureComputerImpl implements MeasureComputer {
 
   public static class MeasureComputerBuilderImpl implements MeasureComputerBuilder {
 
-    private String[] inputMetricKeys;
+    private String[] inputMetricKeys = new String[] {};
     private String[] outputMetrics;
     private Implementation measureComputerImplementation;
 
     @Override
     public MeasureComputerBuilder setInputMetrics(String... inputMetrics) {
-      this.inputMetricKeys = inputMetrics;
-      checkInputMetricKeys();
+      this.inputMetricKeys = validateInputMetricKeys(inputMetrics);
       return this;
     }
 
     @Override
     public MeasureComputerBuilder setOutputMetrics(String... outputMetrics) {
-      this.outputMetrics = outputMetrics;
-      checkOutputMetricKeys();
+      this.outputMetrics = validateOutputMetricKeys(outputMetrics);
       return this;
     }
 
     @Override
     public MeasureComputerBuilder setImplementation(Implementation impl) {
-      this.measureComputerImplementation = impl;
-      checkImplementation();
+      this.measureComputerImplementation = validateImplementation(impl);
       return this;
     }
 
     @Override
     public MeasureComputer build() {
-      checkInputMetricKeys();
-      checkOutputMetricKeys();
-      checkImplementation();
+      validateInputMetricKeys(this.inputMetricKeys);
+      validateOutputMetricKeys(this.outputMetrics);
+      validateImplementation(this.measureComputerImplementation);
       return new MeasureComputerImpl(this);
     }
 
-    private void checkInputMetricKeys(){
-      checkArgument(this.inputMetricKeys != null && inputMetricKeys.length > 0, "At least one input metrics must be defined");
+    private static String[] validateInputMetricKeys(@Nullable String[] inputMetrics) {
+      requireNonNull(inputMetrics, "Input metrics cannot be null");
+      checkNotNull(inputMetrics);
+      return inputMetrics;
     }
 
-    private void checkOutputMetricKeys(){
-      checkArgument(this.outputMetrics != null && outputMetrics.length > 0, "At least one output metrics must be defined");
+    private static String[] validateOutputMetricKeys(@Nullable String[] outputMetrics) {
+      checkArgument(outputMetrics != null && outputMetrics.length > 0, "At least one output metric must be defined");
+      checkNotNull(outputMetrics);
+      return outputMetrics;
     }
 
-    private void checkImplementation(){
-      checkArgument(this.measureComputerImplementation != null, "The implementation is missing");
+    private static Implementation validateImplementation(Implementation impl) {
+      return requireNonNull(impl, "The implementation is missing");
+    }
+  }
+
+  private static void checkNotNull(String[] metrics){
+    for (String metric : metrics) {
+      requireNonNull(metric, "Null metric is not allowed");
     }
   }
 }