fix: #355 Explicitly passing --project argument when starting emulator (#923)

* Running gcloud datastore emulator with --project argument

* Allow user to pass a custom project id when creating a new LocalDatastoreHelper instance

* Creating a local variable to increase the readability and emphasizing on the fact that project id not nullable now

* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

Author: jainsahab

google-cloud-datastore/src/main/java/com/google/cloud/datastore/testing/LocalDatastoreHelper.java

@@ -16,6 +16,8 @@
 
 package com.google.cloud.datastore.testing;
 
+import static com.google.common.base.MoreObjects.firstNonNull;
+
 import com.google.api.core.InternalApi;
 import com.google.cloud.NoCredentials;
 import com.google.cloud.ServiceOptions;
@@ -68,7 +70,9 @@ public class LocalDatastoreHelper extends BaseEmulatorHelper<DatastoreOptions> {
 
   // Common settings
   private static final String CONSISTENCY_FLAG = "--consistency=";
+  private static final String PROJECT_FLAG = "--project=";
   private static final double DEFAULT_CONSISTENCY = 0.9;
+  private static final String DEFAULT_PROJECT_ID = PROJECT_ID_PREFIX + UUID.randomUUID();
 
   private static final Logger LOGGER = Logger.getLogger(LocalDatastoreHelper.class.getName());
 
@@ -90,6 +94,7 @@ public static class Builder {
     private int port;
     private Path dataDir;
     private boolean storeOnDisk = true;
+    private String projectId;
 
     private Builder() {}
 
@@ -109,6 +114,11 @@ public Builder setPort(int port) {
       return this;
     }
 
+    public Builder setProjectId(String projectId) {
+      this.projectId = projectId;
+      return this;
+    }
+
     public Builder setDataDir(Path dataDir) {
       this.dataDir = dataDir;
       return this;
@@ -129,7 +139,8 @@ private LocalDatastoreHelper(Builder builder) {
     super(
         "datastore",
         builder.port > 0 ? builder.port : BaseEmulatorHelper.findAvailablePort(DEFAULT_PORT),
-        PROJECT_ID_PREFIX + UUID.randomUUID().toString());
+        firstNonNull(builder.projectId, DEFAULT_PROJECT_ID));
+    String projectId = firstNonNull(builder.projectId, DEFAULT_PROJECT_ID);
     this.consistency = builder.consistency > 0 ? builder.consistency : DEFAULT_CONSISTENCY;
     this.gcdPath = builder.dataDir;
     this.storeOnDisk = builder.storeOnDisk;
@@ -140,6 +151,7 @@ private LocalDatastoreHelper(Builder builder) {
     List<String> gcloudCommand = new ArrayList<>(Arrays.asList(GCLOUD_CMD_TEXT.split(" ")));
     gcloudCommand.add(GCLOUD_CMD_PORT_FLAG + "localhost:" + getPort());
     gcloudCommand.add(CONSISTENCY_FLAG + builder.consistency);
+    gcloudCommand.add(PROJECT_FLAG + projectId);
     if (!builder.storeOnDisk) {
       gcloudCommand.add("--no-store-on-disk");
     }

google-cloud-datastore/src/test/java/com/google/cloud/datastore/testing/ITLocalDatastoreHelperTest.java

@@ -88,6 +88,14 @@ public void testCreateWithBuilder() {
     assertTrue(incompleteHelper.getProjectId().startsWith(PROJECT_ID_PREFIX));
   }
 
+  @Test
+  public void testCreateWithCustomProjectId() {
+    String customProjectId = "custom-project-id";
+    LocalDatastoreHelper helper =
+        LocalDatastoreHelper.newBuilder().setProjectId(customProjectId).build();
+    assertEquals(customProjectId, helper.getProjectId());
+  }
+
   @Test
   public void testCreateWithToBuilder() throws IOException {
     LocalDatastoreHelper helper =