#47: Fix NPE when branch is orphaned

Where a Pull Request no longer has a target branch - such as happens when the branch is deleted from SonarQube after the Pull Request is analysed - the `base` field in the branch information will be `null`. To prevent a `NullPointerException` being thrown in this scenario, an explicit check is being added for this field being `null` before attempting to extract the text value from it.

src/main/java/com/github/mc1arke/sonarqube/plugin/scanner/CommunityProjectPullRequestsLoader.java

@@ -21,6 +21,7 @@
 import com.google.gson.Gson;
 import com.google.gson.GsonBuilder;
 import com.google.gson.JsonDeserializer;
+import com.google.gson.JsonElement;
 import com.google.gson.JsonObject;
 import org.sonar.api.utils.MessageException;
 import org.sonar.api.utils.log.Logger;
@@ -40,6 +41,7 @@
 import java.text.SimpleDateFormat;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Optional;
 
 /**
  * Loads the Pull Requests currently known by SonarQube from the server component for client applications.
@@ -72,8 +74,9 @@ private static JsonDeserializer<PullRequestInfo> createPullRequestInfoJsonDeseri
             } catch (ParseException e) {
                 LOGGER.warn("Could not parse date from Pull Requests API response. Will use '0' date", e);
             }
+            final String base = Optional.ofNullable(jsonObject.get("base")).map(JsonElement::getAsString).orElse(null);
             return new PullRequestInfo(jsonObject.get("key").getAsString(), jsonObject.get("branch").getAsString(),
-                                       jsonObject.get("base").getAsString(), parsedDate);
+                    base, parsedDate);
         };
     }
 

src/test/java/com/github/mc1arke/sonarqube/plugin/scanner/CommunityProjectPullRequestsLoaderTest.java

@@ -40,6 +40,7 @@
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertTrue;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.Mockito.mock;
@@ -116,6 +117,27 @@ public void testAllPullRequestsFromNonEmptyServerResponseWithInvalidDate() {
         assertEquals("101", responseInfo.getKey());
     }
 
+    @Test
+    public void testAllPullRequestsFromNonEmptyServerResponseWithoutBase() {
+        WsResponse mockResponse = mock(WsResponse.class);
+        when(scannerWsClient.call(any())).thenReturn(mockResponse);
+
+        StringReader stringReader = new StringReader(
+                "{\"pullRequests\":[{\"key\":\"101\",\"title\":\"dummybranch\",\"branch\":\"dummybranch\",\"status\":{\"qualityGateStatus\":\"OK\",\"bugs\":0,\"vulnerabilities\":0,\"codeSmells\":0},\"analysisDate\":\"\"}]}");
+        when(mockResponse.contentReader()).thenReturn(stringReader);
+
+        CommunityProjectPullRequestsLoader testCase = new CommunityProjectPullRequestsLoader(scannerWsClient);
+        ProjectPullRequests response = testCase.load("key");
+        assertFalse(response.isEmpty());
+
+        PullRequestInfo responseInfo = response.get("dummybranch");
+        assertNotNull(responseInfo);
+        assertEquals(0, responseInfo.getAnalysisDate());
+        assertNull(responseInfo.getBase());
+        assertEquals("dummybranch", responseInfo.getBranch());
+        assertEquals("101", responseInfo.getKey());
+    }
+
     @Test
     public void testMessageExceptionOnIOException() {
         WsResponse mockResponse = mock(WsResponse.class);