Merge branch 'stable-3.1'

* stable-3.1:
  Documentation: Fix parentForDeletedProjects in config.md
  Adapt the change in Gerrit core
  Bump Bazel version to 2.2.0
  Bump required Bazel version to 2.1.0
  Upgrade bazlets to latest stable-2.16 to build with 2.16.16 API
  Documentation: Refactor to match other plugin documentation
  Add an empty tools/BUILD file explicitly for Bazel
  Upgrade bazlets to latest stable-2.16
  Upgrade bazlets to latest stable-2.16
  Upgrade bazlets to latest stable-2.15
  Upgrade bazlets to latest stable-2.14
  config.md: Correct formatting of config values

Change-Id: Ib51ef5f829d0b318cffc41c44f83eb56e55a53df

src/main/java/com/googlesource/gerrit/plugins/deleteproject/DeletePreconditions.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/deleteproject/DeletePreconditions.java b/src/main/java/com/googlesource/gerrit/plugins/deleteproject/DeletePreconditions.java
index 05842c4..417c968 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/deleteproject/DeletePreconditions.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/deleteproject/DeletePreconditions.java
@@ -39,7 +39,7 @@
 import com.google.gerrit.server.query.change.InternalChangeQuery;
 import com.google.gerrit.server.restapi.project.ListChildProjects;
 import com.google.gerrit.server.submit.MergeOpRepoManager;
-import com.google.gerrit.server.submit.SubmoduleException;
+import com.google.gerrit.server.submit.SubmoduleConflictException;
 import com.google.gerrit.server.submit.SubmoduleOp;
 import com.google.inject.Inject;
 import com.google.inject.Provider;
@@ -165,7 +165,7 @@
     } catch (RepositoryNotFoundException e) {
       // we're trying to delete the repository,
       // so this exception should not stop us
-    } catch (IOException | SubmoduleException e) {
+    } catch (IOException | SubmoduleConflictException e) {
       throw new CannotDeleteProjectException("Project is subscribed by other projects.", e);
     }
   }

src/main/java/com/googlesource/gerrit/plugins/deleteproject/HideProject.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/deleteproject/HideProject.java b/src/main/java/com/googlesource/gerrit/plugins/deleteproject/HideProject.java
index c5bf8ce..7656726 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/deleteproject/HideProject.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/deleteproject/HideProject.java
@@ -84,7 +84,7 @@
   }
 
   private void createProjectIfMissing(String projectName) throws IOException, RestApiException {
-    if (projectCache.get(Project.nameKey(projectName)) == null) {
+    if (!projectCache.get(Project.nameKey(projectName)).isPresent()) {
       try {
         createProject.apply(TopLevelResource.INSTANCE, IdString.fromDecoded(projectName), null);
       } catch (RestApiException | ConfigInvalidException | PermissionBackendException e) {

src/test/java/com/googlesource/gerrit/plugins/deleteproject/DeleteProjectIT.java

diff --git a/src/test/java/com/googlesource/gerrit/plugins/deleteproject/DeleteProjectIT.java b/src/test/java/com/googlesource/gerrit/plugins/deleteproject/DeleteProjectIT.java
index d83fac7..4960816 100644
--- a/src/test/java/com/googlesource/gerrit/plugins/deleteproject/DeleteProjectIT.java
+++ b/src/test/java/com/googlesource/gerrit/plugins/deleteproject/DeleteProjectIT.java
@@ -19,15 +19,16 @@
 import static com.google.gerrit.acceptance.GitUtil.pushHead;
 import static com.google.gerrit.acceptance.testsuite.project.TestProjectUpdate.allow;
 import static com.google.gerrit.server.group.SystemGroupBackend.REGISTERED_USERS;
+import static com.google.gerrit.server.project.ProjectCache.illegalState;
 import static java.nio.file.StandardCopyOption.REPLACE_EXISTING;
 
 import com.google.common.base.Joiner;
-import com.google.gerrit.acceptance.GerritConfig;
 import com.google.gerrit.acceptance.LightweightPluginDaemonTest;
 import com.google.gerrit.acceptance.RestResponse;
 import com.google.gerrit.acceptance.TestPlugin;
 import com.google.gerrit.acceptance.UseLocalDisk;
 import com.google.gerrit.acceptance.UseSsh;
+import com.google.gerrit.acceptance.config.GerritConfig;
 import com.google.gerrit.acceptance.testsuite.project.ProjectOperations;
 import com.google.gerrit.acceptance.testsuite.request.RequestScopeOperations;
 import com.google.gerrit.common.data.Permission;
@@ -173,7 +174,7 @@
     String cmd = createDeleteCommand("--preserve-git-repository", project.get());
     adminSshSession.exec(cmd);
 
-    ProjectConfig cfg = projectCache.checkedGet(project).getConfig();
+    ProjectConfig cfg = projectCache.get(project).orElseThrow(illegalState(project)).getConfig();
     ProjectState state = cfg.getProject().getState();
 
     assertThat(state).isEqualTo(ProjectState.HIDDEN);