fix: Better error message when subscription path is invalid.

src/main/java/com/google/cloud/pubsublite/spark/PslDataSourceOptions.java

@@ -18,6 +18,7 @@
 
 import static com.google.cloud.pubsublite.internal.wire.ServiceClients.addDefaultSettings;
 
+import com.google.api.gax.rpc.ApiException;
 import com.google.auto.value.AutoValue;
 import com.google.cloud.pubsublite.AdminClient;
 import com.google.cloud.pubsublite.AdminClientSettings;
@@ -79,9 +80,16 @@ public static PslDataSourceOptions fromSparkDataSourceOptions(DataSourceOptions
     options
         .get(Constants.MAX_MESSAGE_PER_BATCH_CONFIG_KEY)
         .ifPresent(mmpb -> builder.setMaxMessagesPerBatch(Long.parseLong(mmpb)));
+    String subscriptionPathVal = options.get(Constants.SUBSCRIPTION_CONFIG_KEY).get();
+    SubscriptionPath subscriptionPath;
+    try {
+      subscriptionPath = SubscriptionPath.parse(subscriptionPathVal);
+    } catch (ApiException e) {
+      throw new IllegalArgumentException(
+          "Unable to parse subscription path " + subscriptionPathVal);
+    }
     return builder
-        .setSubscriptionPath(
-            SubscriptionPath.parse(options.get(Constants.SUBSCRIPTION_CONFIG_KEY).get()))
+        .setSubscriptionPath(subscriptionPath)
         .setFlowControlSettings(
             FlowControlSettings.builder()
                 .setMessagesOutstanding(

src/test/java/com/google/cloud/pubsublite/spark/PslDataSourceOptionsTest.java

@@ -0,0 +1,35 @@
+/*
+ * Copyright 2020 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.cloud.pubsublite.spark;
+
+import static org.junit.Assert.assertThrows;
+
+import com.google.common.collect.ImmutableMap;
+import org.apache.spark.sql.sources.v2.DataSourceOptions;
+import org.junit.Test;
+
+public class PslDataSourceOptionsTest {
+
+  @Test
+  public void testInvalidSubPath() {
+    DataSourceOptions options =
+        new DataSourceOptions(ImmutableMap.of(Constants.SUBSCRIPTION_CONFIG_KEY, "invalid/path"));
+    assertThrows(
+        IllegalArgumentException.class,
+        () -> PslDataSourceOptions.fromSparkDataSourceOptions(options));
+  }
+}