Code review changes

- Changed fieldName to be added first to the fieldName list
- test which verifies that when 'alternate names' are configured they don't affect serialization, and only affect deserialization
- Updated translateToAlternateNames JavaDoc to refer it works like SerializedName#alternate()

gson/src/main/java/com/google/gson/FieldNamingStrategy.java

@@ -16,6 +16,7 @@
 
 package com.google.gson;
 
+import com.google.gson.annotations.SerializedName;
 import java.lang.reflect.Field;
 import java.util.Collections;
 import java.util.List;
@@ -35,13 +36,14 @@ public interface FieldNamingStrategy {
    * Translates the field name into its JSON field name representation.
    *
    * @param f the field object that we are translating
-   * @return the list of possible translated field names.
+   * @return the translated field name.
    * @since 1.3
    */
   public String translateName(Field f);
 
   /**
-   * Translates the field name into its JSON field alternative names representation.
+   * Translates the field name into its JSON field alternative names representation. used for
+   * deserialization only. This is similar to {@link SerializedName#alternate()}.
    *
    * @param f the field object that we are translating
    * @return the list of possible translated field names.

gson/src/main/java/com/google/gson/internal/bind/ReflectiveTypeAdapterFactory.java

@@ -55,6 +55,8 @@
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
 
 /** Type adapter that reflects over the fields and methods of a class. */
 public final class ReflectiveTypeAdapterFactory implements TypeAdapterFactory {
@@ -87,9 +89,9 @@ private List<String> getFieldNames(Field f) {
     SerializedName annotation = f.getAnnotation(SerializedName.class);
     if (annotation == null) {
       String fieldName = fieldNamingPolicy.translateName(f);
-      List<String> fieldNames = new ArrayList<>(fieldNamingPolicy.translateToAlternateNames(f));
-      fieldNames.add(fieldName);
-      return fieldNames;
+      List<String> alternateNames = fieldNamingPolicy.translateToAlternateNames(f);
+      return Stream.concat(Stream.of(fieldName), alternateNames.stream())
+          .collect(Collectors.toList());
     }
 
     String serializedName = annotation.value();

gson/src/test/java/com/google/gson/functional/NamingPolicyTest.java

@@ -261,6 +261,32 @@ public List<String> translateToAlternateNames(Field f) {
     assertThat(deserializedObject.someConstantStringInstanceField).isEqualTo("someValue");
   }
 
+  @Test
+  public void testGsonWithAlternateNamesSerialization() {
+    Gson gson =
+        builder
+            .setFieldNamingStrategy(
+                new FieldNamingStrategy() {
+
+                  @Override
+                  public String translateName(Field f) {
+                    return "some-constant-string-instance-field";
+                  }
+
+                  @Override
+                  public List<String> translateToAlternateNames(Field f) {
+                    return List.of("SomeConstantStringInstanceField");
+                  }
+                })
+            .create();
+    StringWrapper target = new StringWrapper("blah");
+    assertThat(gson.toJson(target))
+        .isEqualTo(
+            "{\"some-constant-string-instance-field\":\""
+                + target.someConstantStringInstanceField
+                + "\"}");
+  }
+
   static final class AtName {
     @SerializedName("@foo")
     String f = "bar";