fix: avoid NPE when constructing dynamic model

Fixes: https://github.ibm.com/arf/planning-sdk-squad/issues/2060

This commit fixes the scenario where an NPE could occur when
constructing an instance of a dynamic model that contains no
dynamic properties.  We were simply missing a null check
prior to using the generated builder class' dynamicProperties field.

Author: padamstx

src/main/java/com/ibm/cloud/sdk/core/service/model/DynamicModel.java

@@ -85,7 +85,10 @@ public T get(String key) {
    *         a map containing arbitrary properties to set on this object
    */
   public void setProperties(Map<String, T> properties) {
-    this.dynamicProperties = new HashMap<String, T>(properties);
+    this.dynamicProperties = new HashMap<String, T>();
+    if (properties != null) {
+      this.dynamicProperties.putAll(properties);
+    }
   }
 
   /**

src/main/java/com/ibm/cloud/sdk/core/util/GsonSingleton.java

@@ -98,7 +98,7 @@ public static synchronized Gson getGsonWithoutPrettyPrinting() {
 
   /**
    * Returns an instance of Gson with the "serialize nulls" config option enabled.
-   * @return
+   * @return a Gson instance configured to serialize nulls
    */
   public static Gson getGsonWithSerializeNulls() {
     return createGson(false, true);

src/test/java/com/ibm/cloud/sdk/core/test/model/DiscriminatorSerializationTest.java

@@ -39,9 +39,9 @@
 import com.ibm.cloud.sdk.core.util.GsonSingleton;
 
 /**
- * This class contains tests of our DynamicModelTypeAdapterFactory.
- * The test data consists of a few dynamic models that were generated by the java generator
- * and then copied here to this project.
+ * This class contains tests of our DynamicModelTypeAdapterFactory. The test
+ * data consists of a few dynamic models that were generated by the java
+ * generator and then copied here to this project.
  */
 public class DiscriminatorSerializationTest {
   private boolean displayOutput = false;
@@ -82,27 +82,16 @@ private Truck createTruck(String discValue) {
   }
 
   private AnimalDog createDog(String discValue) {
-    AnimalDog model = new AnimalDog();
-    model.setAnimalType(discValue);
-    model.setBreed("Black Lab");
-    model.put("collar_size", "XL");
-    return model;
+    return new AnimalDog.Builder().animalType(discValue).breed("Black Lab").add("collar_size", "XL").build();
   }
 
   private AnimalCat createCat(String discValue) {
-    AnimalCat model = new AnimalCat();
-    model.setAnimalType(discValue);
-    model.setColor("brown");
-    model.put("collar_size", "S");
-    return model;
+    return new AnimalCat.Builder().animalType(discValue).color("brown").add("collar_size", "S").build();
   }
 
   private AnimalIguana createIguana(String discValue) {
-    AnimalIguana model = new AnimalIguana();
-    model.setAnimalType(discValue);
-    model.setTailLength(Long.valueOf(10));
-    model.put("collar_size", "L");
-    return model;
+    return new AnimalIguana.Builder().animalType(discValue).tailLength(Long.valueOf(10)).add("collar_size", "L")
+        .build();
   }
 
   @Test
@@ -117,7 +106,8 @@ public void testTruck() {
     testSerDeser(model, Vehicle.class, Truck.class);
   }
 
-  // These classes simulate generated model classes that contain a list/map of discriminated oneOf parents.
+  // These classes simulate generated model classes that contain a list/map of
+  // discriminated oneOf parents.
   public class VehicleHolder {
     int size;
     List<Vehicle> vehicles;
@@ -141,13 +131,15 @@ public AnimalHolder(Map<String, Animal> animals) {
   @Test
   public void testVehicleList() {
 
-    // Create an instance of VehicleHolder that contains a list of Vehicle instances.
+    // Create an instance of VehicleHolder that contains a list of Vehicle
+    // instances.
     List<Vehicle> vehicleList = new ArrayList<>();
     vehicleList.add(createTruck("truck"));
     vehicleList.add(createCar("Car"));
     VehicleHolder expected = new VehicleHolder(vehicleList);
 
-    // Make sure we can serialize the model instance containing the list of oneOf parents.
+    // Make sure we can serialize the model instance containing the list of oneOf
+    // parents.
     String json = serialize(expected);
     assertNotNull(json);
     log("Vehicle holder (json): " + json);
@@ -230,7 +222,8 @@ public void testAnimalsNullElement() {
     animals.put("missing_dog", null);
     AnimalHolder expected = new AnimalHolder(animals);
 
-    // We have to enable "serialize nulls" because Gson's handling of maps seems to be inconsistent with their
+    // We have to enable "serialize nulls" because Gson's handling of maps seems to
+    // be inconsistent with their
     // support of lists.
     String json = GsonSingleton.getGsonWithSerializeNulls().toJson(expected);
     assertNotNull(json);
@@ -242,19 +235,19 @@ public void testAnimalsNullElement() {
     assertEquals(actual.animals, expected.animals);
   }
 
-  @Test(expectedExceptions = {JsonSyntaxException.class})
+  @Test(expectedExceptions = { JsonSyntaxException.class })
   void testTruckDiscPropMissing() {
     Truck model = createTruck(null);
     testSerDeser(model, Vehicle.class, Truck.class);
   }
 
-  @Test(expectedExceptions = {JsonSyntaxException.class})
+  @Test(expectedExceptions = { JsonSyntaxException.class })
   void testTruckEmptyDiscValue() {
     Truck model = createTruck("");
     testSerDeser(model, Vehicle.class, Truck.class);
   }
 
-  @Test(expectedExceptions = {JsonSyntaxException.class})
+  @Test(expectedExceptions = { JsonSyntaxException.class })
   void testCarBadDiscValue() {
     Car model = createCar("LAMBO");
     testSerDeser(model, Vehicle.class, Car.class);

src/test/java/com/ibm/cloud/sdk/core/test/model/DynamicModelTest.java

@@ -0,0 +1,102 @@
+/**
+ * (C) Copyright IBM Corp. 2015, 2019.
+ *
+ * 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.ibm.cloud.sdk.core.test.model;
+
+import static org.testng.Assert.assertEquals;
+import static org.testng.Assert.assertNotEquals;
+import static org.testng.Assert.assertNotNull;
+import static org.testng.Assert.assertTrue;
+
+import org.testng.annotations.Test;
+
+import com.ibm.cloud.sdk.core.test.model.generated.AnimalCat;
+
+/**
+ * A few simple tests that exercise the GenericModel methods.
+ */
+public class DynamicModelTest {
+  private boolean displayOutput = false;
+
+  private void log(String msg) {
+    if (displayOutput) {
+      System.out.println(msg);
+    }
+  }
+
+  private AnimalCat createCat(String color, String propName, String propValue) {
+    AnimalCat.Builder builder = new AnimalCat.Builder()
+        .color(color)
+        .animalType("Cat");
+    if (propName != null) {
+      builder.add(propName, propValue);
+    }
+    return builder.build();
+  }
+
+  @Test
+  public void testEquals1() {
+    AnimalCat cat1 = createCat("brown", null, null);
+    assertNotNull(cat1);
+
+    AnimalCat cat2 = createCat("brown", null, null);
+    assertNotNull(cat2);
+
+    assertEquals(cat1, cat2);
+  }
+
+  @Test
+  public void testEquals2() {
+    AnimalCat cat1 = createCat("brown", "prop", "value");
+    assertNotNull(cat1);
+
+    AnimalCat cat2 = createCat("brown", "prop", "value");
+    assertNotNull(cat2);
+
+    assertEquals(cat1, cat2);
+    log("cat1: " + cat1.toString());
+    log("cat2: " + cat2.toString());
+  }
+
+  @Test
+  public void testNotEquals1() {
+    AnimalCat cat1 = createCat("brown", "prop1", "value");
+    assertNotNull(cat1);
+
+    AnimalCat cat2 = createCat("brown", null, null);
+    assertNotNull(cat2);
+
+    assertNotEquals(cat1, cat2);
+  }
+
+  @Test
+  public void testNotEquals2() {
+    AnimalCat cat1 = createCat("brown", "prop1", "value");
+    assertNotNull(cat1);
+
+    AnimalCat cat2 = createCat("brown", "prop2", "value");
+    assertNotNull(cat2);
+
+    assertNotEquals(cat1, cat2);
+  }
+
+  @Test
+  public void testNullAdditionalProperty() {
+    AnimalCat cat = createCat("brown", "prop1", null);
+    assertNotNull(cat);
+    log("cat: " + cat.toString());
+
+    assertTrue(cat.toString().contains("\"prop1\": null"));
+  }
+
+}

src/test/java/com/ibm/cloud/sdk/core/test/model/generated/Animal.java

@@ -1,5 +1,5 @@
 /*
- * (C) Copyright IBM Corp. 2019.
+ * (C) Copyright IBM Corp. 2019, 2020.
  *
  * 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

src/test/java/com/ibm/cloud/sdk/core/test/model/generated/AnimalCat.java

@@ -1,5 +1,5 @@
 /*
- * (C) Copyright IBM Corp. 2019.
+ * (C) Copyright IBM Corp. 2019, 2020.
  *
  * 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
@@ -12,6 +12,9 @@
  */
 package com.ibm.cloud.sdk.core.test.model.generated;
 
+import java.util.HashMap;
+import java.util.Map;
+
 /**
  * Information about a cat.
  */
@@ -22,6 +25,104 @@ public AnimalCat() {
     super();
   }
 
+  /**
+   * Builder.
+   */
+  public static class Builder {
+    private String animalType;
+    private String color;
+    private Map<String, String> dynamicProperties;
+
+    public Builder(Animal animalCat) {
+      this.animalType = animalCat.animalType;
+      this.color = animalCat.color;
+      this.dynamicProperties = animalCat.getProperties();
+    }
+
+    /**
+     * Instantiates a new builder.
+     */
+    public Builder() {
+    }
+
+    /**
+     * Instantiates a new builder with required properties.
+     *
+     * @param animalType the animalType
+     * @param color the color
+     */
+    public Builder(String animalType, String color) {
+      this.animalType = animalType;
+      this.color = color;
+    }
+
+    /**
+     * Builds a AnimalCat.
+     *
+     * @return the new AnimalCat instance
+     */
+    public AnimalCat build() {
+      return new AnimalCat(this);
+    }
+
+    /**
+     * Set the animalType.
+     *
+     * @param animalType the animalType
+     * @return the AnimalCat builder
+     */
+    public Builder animalType(String animalType) {
+      this.animalType = animalType;
+      return this;
+    }
+
+    /**
+     * Set the color.
+     *
+     * @param color the color
+     * @return the AnimalCat builder
+     */
+    public Builder color(String color) {
+      this.color = color;
+      return this;
+    }
+
+    /**
+     * Add an arbitrary property.
+     *
+     * @param name the name of the property to add
+     * @param value the value of the property to add
+     * @return the AnimalCat builder
+     */
+    public Builder add(String name, String value) {
+      com.ibm.cloud.sdk.core.util.Validator.notNull(name, "name cannot be null");
+      if (this.dynamicProperties == null) {
+        this.dynamicProperties = new HashMap<String, String>();
+      }
+      this.dynamicProperties.put(name, value);
+      return this;
+    }
+  }
+
+  protected AnimalCat(Builder builder) {
+    com.ibm.cloud.sdk.core.util.Validator.notNull(builder.animalType,
+      "animalType cannot be null");
+    com.ibm.cloud.sdk.core.util.Validator.notNull(builder.color,
+      "color cannot be null");
+    animalType = builder.animalType;
+    color = builder.color;
+    this.setProperties(builder.dynamicProperties);
+  }
+
+  /**
+   * New builder.
+   *
+   * @return a AnimalCat builder
+   */
+  public Builder newBuilder() {
+    return new Builder(this);
+  }
+
   /**
    * Sets the animalType.
    *