Remove invalid hints from Properties inputs.

hoptimator-util/src/main/java/com/linkedin/hoptimator/util/DeploymentService.java

@@ -29,7 +29,7 @@
 
 public final class DeploymentService {
 
-  private static final String HINT_OPTION = "hints";
+  static final String HINT_OPTION = "hints";
   public static final String PIPELINE_OPTION = "pipeline";
 
   private DeploymentService() {
@@ -97,11 +97,19 @@ public static PipelineRel.Implementor plan(RelRoot root, List<RelOptMaterializat
   public static Map<String, String> parseHints(Properties connectionProperties) {
     Map<String, String> hints = new LinkedHashMap<>();
     if (connectionProperties.containsKey(HINT_OPTION)) {
-      hints.putAll(Splitter.on(',').withKeyValueSeparator('=').split(connectionProperties.getProperty(HINT_OPTION)));
+      String property = connectionProperties.getProperty(HINT_OPTION);
+      if (property != null && !property.isEmpty()) {
+        hints.putAll(Splitter.on(',').withKeyValueSeparator('=').split(property));
+      }
     }
+
     if (connectionProperties.containsKey(PIPELINE_OPTION)) {
-      hints.put(PIPELINE_OPTION, connectionProperties.getProperty(PIPELINE_OPTION));
+      String property = connectionProperties.getProperty(PIPELINE_OPTION);
+      if (property != null && !property.isEmpty()) {
+        hints.put(PIPELINE_OPTION, property);
+      }
     }
+
     return hints;
   }
 }

hoptimator-util/src/test/java/com/linkedin/hoptimator/util/DeploymentServiceTest.java

@@ -0,0 +1,54 @@
+package com.linkedin.hoptimator.util;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import java.util.Properties;
+
+import org.junit.jupiter.api.Test;
+
+import static com.linkedin.hoptimator.util.DeploymentService.HINT_OPTION;
+import static com.linkedin.hoptimator.util.DeploymentService.PIPELINE_OPTION;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+
+
+class DeploymentServiceTest {
+
+  /**
+   * "hint" keys <b>and</b> values are required to be non-{@code null}. An
+   * empty {@link Map} is considered invalid and should <b>not</b> be added
+   * to the {@link Properties} object.
+   * <br/>
+   * nb. "pipeline" values are <b>always</b> added when present.
+   */
+  @Test
+  void parseHints() {
+    Map<String, String> empty = DeploymentService.parseHints(new Properties());
+    assertTrue(empty.isEmpty(), "An empty map should not add `hints`.");
+
+    Map<String, String> defined = DeploymentService.parseHints(new Properties() {{
+      put(HINT_OPTION, "key=value");
+    }});
+    assertEquals("value", defined.get("key"), "Did not match expected key value pair: `key=value`.");
+
+    Map<String, String> nokey = DeploymentService.parseHints(new Properties() {{
+      put(HINT_OPTION, "flag0=,flag1=");
+    }});
+    assertTrue(nokey.keySet().containsAll(Arrays.asList("flag0", "flag1")), "Expected to find flags.");
+
+    Map<String, String> pipelineOnly = DeploymentService.parseHints(new Properties() {{
+      put(PIPELINE_OPTION, "pipeline");
+    }});
+    assertEquals("pipeline", pipelineOnly.get(PIPELINE_OPTION), "Did not match expected `pipeline` value.");
+
+    Map<String, String> both = DeploymentService.parseHints(new Properties() {{
+      putAll(defined);
+      put(PIPELINE_OPTION, "pipeline");
+    }});
+    assertEquals("pipeline", both.get(PIPELINE_OPTION), "Did not match expected `pipeline` value.");
+  }
+}