wrap lookup command result in java.util.Optional to clarify api

scm-core/src/main/java/sonia/scm/repository/api/LookupCommandBuilder.java

@@ -27,6 +27,8 @@ package sonia.scm.repository.api;
 import sonia.scm.repository.spi.LookupCommand;
 import sonia.scm.repository.spi.LookupCommandRequest;
 
+import java.util.Optional;
+
 /**
  * The lookup command executes a lookup for additional repository information.
  *
@@ -41,7 +43,7 @@ public class LookupCommandBuilder {
     this.lookupCommand = lookupCommand;
   }
 
-  public <T> T lookup(Class<T> type, String... args) {
+  public <T> Optional<T> lookup(Class<T> type, String... args) {
     request.setType(type);
     request.setArgs(args);
     return lookupCommand.lookup(request);

scm-core/src/main/java/sonia/scm/repository/spi/LookupCommand.java

@@ -24,12 +24,15 @@
 
 package sonia.scm.repository.spi;
 
+import java.util.Optional;
+
 public interface LookupCommand {
 
   /**
    * Executes lookup for given parameters.
+   *
    * @param request Arguments provided for the lookup.
    * @return Result of provided type.
    */
-  <T> T lookup(LookupCommandRequest request);
+  <T> Optional<T> lookup(LookupCommandRequest request);
 }

scm-plugins/scm-svn-plugin/src/main/java/sonia/scm/repository/spi/SvnLookupCommand.java

@@ -29,6 +29,7 @@ import org.tmatesoft.svn.core.SVNException;
 import org.tmatesoft.svn.core.io.SVNRepository;
 
 import java.util.Arrays;
+import java.util.Optional;
 
 @Slf4j
 public class SvnLookupCommand extends AbstractSvnCommand implements LookupCommand {
@@ -38,18 +39,28 @@ public class SvnLookupCommand extends AbstractSvnCommand implements LookupComman
   }
 
   @Override
-  public <T> T lookup(LookupCommandRequest request) {
+  public <T> Optional<T> lookup(LookupCommandRequest request) {
     try {
-      SVNRepository repository = context.open();
-      if (request.getArgs()[0].equalsIgnoreCase("props")) {
-        if (Arrays.stream(request.getArgs()).anyMatch(a -> a.equalsIgnoreCase("uuid"))) {
-          return (T) repository.getRepositoryUUID(false);
-        }
+      if (requestContainsArg(request, "props")) {
+        return lookupProps(request);
       }
-    } catch (SVNException | ClassCastException e) {
-      log.error("Invalid lookup request", e);
+    } catch (SVNException e) {
+      log.error("Lookup failed: ", e);
     }
 
-    return null;
+    return Optional.empty();
+  }
+
+  private <T> Optional<T> lookupProps(LookupCommandRequest request) throws SVNException {
+    if (requestContainsArg(request, "uuid")) {
+      SVNRepository repository = context.open();
+      return Optional.of((T) repository.getRepositoryUUID(true));
+    }
+    log.debug("No result found on lookup");
+    return Optional.empty();
+  }
+
+  private boolean requestContainsArg(LookupCommandRequest request, String props) {
+    return Arrays.stream(request.getArgs()).anyMatch(a -> a.equalsIgnoreCase(props));
   }
 }

scm-plugins/scm-svn-plugin/src/test/java/sonia/scm/repository/spi/SvnLookupCommandTest.java

@@ -0,0 +1,80 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2020-present Cloudogu GmbH and Contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package sonia.scm.repository.spi;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.InjectMocks;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+import org.tmatesoft.svn.core.SVNException;
+import org.tmatesoft.svn.core.io.SVNRepository;
+
+import java.util.Optional;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.Mockito.when;
+
+@ExtendWith(MockitoExtension.class)
+class SvnLookupCommandTest {
+
+  @Mock
+  SvnContext context;
+
+  @Mock
+  SVNRepository svnRepository;
+
+  @InjectMocks
+  SvnLookupCommand command;
+
+  @Test
+  void shouldReturnEmptyOptional() {
+    LookupCommandRequest request = new LookupCommandRequest();
+    request.setType(String.class);
+    request.setArgs(new String[]{"props"});
+
+    Optional<Object> result = command.lookup(request);
+
+    assertThat(result).isNotPresent();
+  }
+
+  @Test
+  void shouldReturnRepositoryUUID() throws SVNException {
+    String uuid = "trillian-hitchhiker-42";
+    when(context.open()).thenReturn(svnRepository);
+    when(svnRepository.getRepositoryUUID(true)).thenReturn(uuid);
+
+    LookupCommandRequest request = new LookupCommandRequest();
+    request.setType(String.class);
+    request.setArgs(new String[]{"props", "uuid"});
+
+    Optional<Object> result = command.lookup(request);
+
+    assertThat(result).isPresent();
+    assertThat(result.get())
+      .isInstanceOf(String.class)
+      .isEqualTo(uuid);
+  }
+}