SONAR-22009 Fix NPE on SARIF import when Extensions don't have Rules

sonar-core/src/main/java/org/sonar/core/sarif/Extension.java

 
 import com.google.gson.annotations.SerializedName;
 import java.util.Set;
+import javax.annotation.CheckForNull;
 
 public class Extension {
   @SerializedName("rules")
     // http://stackoverflow.com/a/18645370/229031
   }
 
+  @CheckForNull
   public Set<Rule> getRules() {
     return rules;
   }

sonar-scanner-engine/src/main/java/org/sonar/scanner/externalissue/sarif/RunMapper.java

 import org.sonar.api.batch.sensor.rule.NewAdHocRule;
 import org.sonar.api.scanner.ScannerSide;
 import org.sonar.core.sarif.Driver;
+import org.sonar.core.sarif.Extension;
 import org.sonar.core.sarif.Result;
 import org.sonar.core.sarif.Rule;
 import org.sonar.core.sarif.Run;
   private List<NewAdHocRule> toNewAdHocRules(Run run, String driverName, Map<String, String> ruleSeveritiesByRuleId, Map<String, String> ruleSeveritiesByRuleIdForNewCCT) {
     Set<Rule> driverRules = run.getTool().getDriver().getRules();
     Set<Rule> extensionRules = hasExtensions(run.getTool())
-      ? run.getTool().getExtensions().stream().flatMap(extension -> extension.getRules().stream()).collect(toSet())
+      ? run.getTool().getExtensions().stream().filter(RunMapper::hasRules).flatMap(extension -> extension.getRules().stream()).collect(toSet())
       : Set.of();
     return Stream.concat(driverRules.stream(), extensionRules.stream())
       .distinct()
     return tool.getExtensions() != null && !tool.getExtensions().isEmpty();
   }
 
+  private static boolean hasRules(Extension extension) {
+    return extension.getRules() != null && !extension.getRules().isEmpty();
+  }
+
   private List<NewExternalIssue> toNewExternalIssues(Run run, String driverName, Map<String, String> ruleSeveritiesByRuleId, Map<String, String> ruleSeveritiesByRuleIdForNewCCT) {
     return run.getResults()
       .stream()

sonar-scanner-engine/src/test/java/org/sonar/scanner/externalissue/sarif/RunMapperTest.java

 import static java.util.Collections.emptySet;
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
+import static org.assertj.core.api.Assertions.assertThatNoException;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.mockStatic;
 import static org.mockito.Mockito.when;
     }
   }
 
+  @Test
+  public void mapRun_shouldNotFail_whenExtensionsDontHaveRules() {
+    when(run.getTool().getDriver().getRules()).thenReturn(Set.of(rule));
+    Extension extension = mock(Extension.class);
+    when(extension.getRules()).thenReturn(null);
+    when(run.getTool().getExtensions()).thenReturn(Set.of(extension));
+
+    try (MockedStatic<RulesSeverityDetector> detector = mockStatic(RulesSeverityDetector.class)) {
+      detector.when(() -> RulesSeverityDetector.detectRulesSeverities(run, TEST_DRIVER)).thenReturn(Map.of(RULE_ID, WARNING));
+      detector.when(() -> RulesSeverityDetector.detectRulesSeveritiesForNewTaxonomy(run, TEST_DRIVER)).thenReturn(Map.of(RULE_ID, WARNING));
+
+      assertThatNoException().isThrownBy(() -> runMapper.mapRun(run));
+    }
+  }
+
+  @Test
+  public void mapRun_shouldNotFail_whenExtensionsHaveEmptyRules() {
+    when(run.getTool().getDriver().getRules()).thenReturn(Set.of(rule));
+    Extension extension = mock(Extension.class);
+    when(extension.getRules()).thenReturn(Set.of());
+    when(run.getTool().getExtensions()).thenReturn(Set.of(extension));
+
+    try (MockedStatic<RulesSeverityDetector> detector = mockStatic(RulesSeverityDetector.class)) {
+      detector.when(() -> RulesSeverityDetector.detectRulesSeverities(run, TEST_DRIVER)).thenReturn(Map.of(RULE_ID, WARNING));
+      detector.when(() -> RulesSeverityDetector.detectRulesSeveritiesForNewTaxonomy(run, TEST_DRIVER)).thenReturn(Map.of(RULE_ID, WARNING));
+
+      assertThatNoException().isThrownBy(() -> runMapper.mapRun(run));
+    }
+  }
+
   @Test
   public void mapRun_ifRunIsEmpty_returnsEmptyList() {
     when(run.getResults()).thenReturn(emptySet());