Fail Maven build on compiler warnings; remove some warning suppressions

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

@@ -503,12 +503,13 @@ private static TypeAdapter<AtomicLongArray> atomicLongArrayAdapter(final TypeAda
    * @throws IllegalArgumentException if this GSON cannot serialize and
    *     deserialize {@code type}.
    */
-  @SuppressWarnings("unchecked")
   public <T> TypeAdapter<T> getAdapter(TypeToken<T> type) {
     Objects.requireNonNull(type, "type must not be null");
     TypeAdapter<?> cached = typeTokenCache.get(type);
     if (cached != null) {
-      return (TypeAdapter<T>) cached;
+      @SuppressWarnings("unchecked")
+      TypeAdapter<T> adapter = (TypeAdapter<T>) cached;
+      return adapter;
     }
 
     Map<TypeToken<?>, FutureTypeAdapter<?>> threadCalls = calls.get();
@@ -520,6 +521,7 @@ public <T> TypeAdapter<T> getAdapter(TypeToken<T> type) {
     }
 
     // the key and value type parameters always agree
+    @SuppressWarnings("unchecked")
     FutureTypeAdapter<T> ongoingCall = (FutureTypeAdapter<T>) threadCalls.get(type);
     if (ongoingCall != null) {
       return ongoingCall;
@@ -532,6 +534,7 @@ public <T> TypeAdapter<T> getAdapter(TypeToken<T> type) {
       for (TypeAdapterFactory factory : factories) {
         TypeAdapter<T> candidate = factory.create(this, type);
         if (candidate != null) {
+          @SuppressWarnings("unchecked")
           TypeAdapter<T> existingAdapter = (TypeAdapter<T>) typeTokenCache.putIfAbsent(type, candidate);
           // If other thread concurrently added adapter prefer that one instead
           if (existingAdapter != null) {
@@ -780,17 +783,17 @@ public void toJson(Object src, Type typeOfSrc, Appendable writer) throws JsonIOE
    *
    * @throws JsonIOException if there was a problem writing to the writer
    */
-  @SuppressWarnings("unchecked")
   public void toJson(Object src, Type typeOfSrc, JsonWriter writer) throws JsonIOException {
-    TypeAdapter<?> adapter = getAdapter(TypeToken.get(typeOfSrc));
+    @SuppressWarnings("unchecked")
+    TypeAdapter<Object> adapter = (TypeAdapter<Object>) getAdapter(TypeToken.get(typeOfSrc));
     boolean oldLenient = writer.isLenient();
     writer.setLenient(true);
     boolean oldHtmlSafe = writer.isHtmlSafe();
     writer.setHtmlSafe(htmlSafe);
     boolean oldSerializeNulls = writer.getSerializeNulls();
     writer.setSerializeNulls(serializeNulls);
     try {
-      ((TypeAdapter<Object>) adapter).write(writer, src);
+      adapter.write(writer, src);
     } catch (IOException e) {
       throw new JsonIOException(e);
     } catch (AssertionError e) {
@@ -957,12 +960,12 @@ public <T> T fromJson(String json, Class<T> classOfT) throws JsonSyntaxException
    * @throws JsonParseException if json is not a valid representation for an object of type typeOfT
    * @throws JsonSyntaxException if json is not a valid representation for an object of type
    */
-  @SuppressWarnings("unchecked")
   public <T> T fromJson(String json, Type typeOfT) throws JsonSyntaxException {
     if (json == null) {
       return null;
     }
     StringReader reader = new StringReader(json);
+    @SuppressWarnings("unchecked")
     T target = (T) fromJson(reader, typeOfT);
     return target;
   }
@@ -1017,9 +1020,9 @@ public <T> T fromJson(Reader json, Class<T> classOfT) throws JsonSyntaxException
    * @throws JsonSyntaxException if json is not a valid representation for an object of type
    * @since 1.2
    */
-  @SuppressWarnings("unchecked")
   public <T> T fromJson(Reader json, Type typeOfT) throws JsonIOException, JsonSyntaxException {
     JsonReader jsonReader = newJsonReader(json);
+    @SuppressWarnings("unchecked")
     T object = (T) fromJson(jsonReader, typeOfT);
     assertFullConsumption(object, jsonReader);
     return object;
@@ -1052,14 +1055,14 @@ private static void assertFullConsumption(Object obj, JsonReader reader) {
    * @throws JsonIOException if there was a problem writing to the Reader
    * @throws JsonSyntaxException if json is not a valid representation for an object of type
    */
-  @SuppressWarnings("unchecked")
   public <T> T fromJson(JsonReader reader, Type typeOfT) throws JsonIOException, JsonSyntaxException {
     boolean isEmpty = true;
     boolean oldLenient = reader.isLenient();
     reader.setLenient(true);
     try {
       reader.peek();
       isEmpty = false;
+      @SuppressWarnings("unchecked")
       TypeToken<T> typeToken = (TypeToken<T>) TypeToken.get(typeOfT);
       TypeAdapter<T> typeAdapter = getAdapter(typeToken);
       T object = typeAdapter.read(reader);

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

@@ -541,22 +541,23 @@ public GsonBuilder setDateFormat(int dateStyle, int timeStyle) {
    * {@link InstanceCreator}, {@link JsonSerializer}, and a {@link JsonDeserializer} interfaces.
    * @return a reference to this {@code GsonBuilder} object to fulfill the "Builder" pattern
    */
-  @SuppressWarnings({"unchecked", "rawtypes"})
   public GsonBuilder registerTypeAdapter(Type type, Object typeAdapter) {
     Objects.requireNonNull(type);
     $Gson$Preconditions.checkArgument(typeAdapter instanceof JsonSerializer<?>
         || typeAdapter instanceof JsonDeserializer<?>
         || typeAdapter instanceof InstanceCreator<?>
         || typeAdapter instanceof TypeAdapter<?>);
     if (typeAdapter instanceof InstanceCreator<?>) {
-      instanceCreators.put(type, (InstanceCreator) typeAdapter);
+      instanceCreators.put(type, (InstanceCreator<?>) typeAdapter);
     }
     if (typeAdapter instanceof JsonSerializer<?> || typeAdapter instanceof JsonDeserializer<?>) {
       TypeToken<?> typeToken = TypeToken.get(type);
       factories.add(TreeTypeAdapter.newFactoryWithMatchRawType(typeToken, typeAdapter));
     }
     if (typeAdapter instanceof TypeAdapter<?>) {
-      factories.add(TypeAdapters.newFactory(TypeToken.get(type), (TypeAdapter)typeAdapter));
+      @SuppressWarnings({"unchecked", "rawtypes"})
+      TypeAdapterFactory factory = TypeAdapters.newFactory(TypeToken.get(type), (TypeAdapter)typeAdapter);
+      factories.add(factory);
     }
     return this;
   }
@@ -589,7 +590,6 @@ public GsonBuilder registerTypeAdapterFactory(TypeAdapterFactory factory) {
    * @return a reference to this {@code GsonBuilder} object to fulfill the "Builder" pattern
    * @since 1.7
    */
-  @SuppressWarnings({"unchecked", "rawtypes"})
   public GsonBuilder registerTypeHierarchyAdapter(Class<?> baseType, Object typeAdapter) {
     Objects.requireNonNull(baseType);
     $Gson$Preconditions.checkArgument(typeAdapter instanceof JsonSerializer<?>
@@ -599,7 +599,9 @@ public GsonBuilder registerTypeHierarchyAdapter(Class<?> baseType, Object typeAd
       hierarchyFactories.add(TreeTypeAdapter.newTypeHierarchyFactory(baseType, typeAdapter));
     }
     if (typeAdapter instanceof TypeAdapter<?>) {
-      factories.add(TypeAdapters.newTypeHierarchyFactory(baseType, (TypeAdapter)typeAdapter));
+      @SuppressWarnings({"unchecked", "rawtypes"})
+      TypeAdapterFactory factory = TypeAdapters.newTypeHierarchyFactory(baseType, (TypeAdapter)typeAdapter);
+      factories.add(factory);
     }
     return this;
   }

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

@@ -35,7 +35,6 @@
  */
 public final class ArrayTypeAdapter<E> extends TypeAdapter<Object> {
   public static final TypeAdapterFactory FACTORY = new TypeAdapterFactory() {
-    @SuppressWarnings({"unchecked", "rawtypes"})
     @Override public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> typeToken) {
       Type type = typeToken.getType();
       if (!(type instanceof GenericArrayType || type instanceof Class && ((Class<?>) type).isArray())) {
@@ -44,8 +43,11 @@ public final class ArrayTypeAdapter<E> extends TypeAdapter<Object> {
 
       Type componentType = $Gson$Types.getArrayComponentType(type);
       TypeAdapter<?> componentTypeAdapter = gson.getAdapter(TypeToken.get(componentType));
-      return new ArrayTypeAdapter(
+
+      @SuppressWarnings({"unchecked", "rawtypes"})
+      TypeAdapter<T> arrayAdapter = new ArrayTypeAdapter(
               gson, componentTypeAdapter, $Gson$Types.getRawType(componentType));
+      return arrayAdapter;
     }
   };
 
@@ -89,7 +91,6 @@ public ArrayTypeAdapter(Gson context, TypeAdapter<E> componentTypeAdapter, Class
     }
   }
 
-  @SuppressWarnings("unchecked")
   @Override public void write(JsonWriter out, Object array) throws IOException {
     if (array == null) {
       out.nullValue();
@@ -98,6 +99,7 @@ public ArrayTypeAdapter(Gson context, TypeAdapter<E> componentTypeAdapter, Class
 
     out.beginArray();
     for (int i = 0, length = Array.getLength(array); i < length; i++) {
+      @SuppressWarnings("unchecked")
       E value = (E) Array.get(array, i);
       componentTypeAdapter.write(out, value);
     }

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

@@ -38,7 +38,7 @@ public JsonAdapterAnnotationTypeAdapterFactory(ConstructorConstructor constructo
     this.constructorConstructor = constructorConstructor;
   }
 
-  @SuppressWarnings("unchecked")
+  @SuppressWarnings("unchecked") // this is not safe; requires that user has specified correct adapter class for @JsonAdapter
   @Override
   public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> targetType) {
     Class<? super T> rawType = targetType.getRawType();
@@ -49,7 +49,6 @@ public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> targetType) {
     return (TypeAdapter<T>) getTypeAdapter(constructorConstructor, gson, targetType, annotation);
   }
 
-  @SuppressWarnings({ "unchecked", "rawtypes" }) // Casts guarded by conditionals.
   TypeAdapter<?> getTypeAdapter(ConstructorConstructor constructorConstructor, Gson gson,
       TypeToken<?> type, JsonAdapter annotation) {
     Object instance = constructorConstructor.get(TypeToken.get(annotation.value())).construct();
@@ -67,7 +66,11 @@ TypeAdapter<?> getTypeAdapter(ConstructorConstructor constructorConstructor, Gso
       JsonDeserializer<?> deserializer = instance instanceof JsonDeserializer
           ? (JsonDeserializer<?>) instance
           : null;
-      typeAdapter = new TreeTypeAdapter(serializer, deserializer, gson, type, null, nullSafe);
+
+      @SuppressWarnings({ "unchecked", "rawtypes" })
+      TypeAdapter<?> tempAdapter = new TreeTypeAdapter(serializer, deserializer, gson, type, null, nullSafe);
+      typeAdapter = tempAdapter;
+
       nullSafe = false;
     } else {
       throw new IllegalArgumentException("Invalid attempt to bind an instance of "

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

@@ -166,13 +166,13 @@ private Object readTerminal(JsonReader in, JsonToken peeked) throws IOException
     }
   }
 
-  @SuppressWarnings("unchecked")
   @Override public void write(JsonWriter out, Object value) throws IOException {
     if (value == null) {
       out.nullValue();
       return;
     }
 
+    @SuppressWarnings("unchecked")
     TypeAdapter<Object> typeAdapter = (TypeAdapter<Object>) gson.getAdapter(value.getClass());
     if (typeAdapter instanceof ObjectTypeAdapter) {
       out.beginObject();

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

@@ -126,10 +126,10 @@ private ReflectiveTypeAdapterFactory.BoundField createBoundField(
       final TypeToken<?> fieldType, boolean serialize, boolean deserialize,
       final boolean blockInaccessible) {
     final boolean isPrimitive = Primitives.isPrimitive(fieldType.getRawType());
-    // special casing primitives here saves ~5% on Android...
     JsonAdapter annotation = field.getAnnotation(JsonAdapter.class);
     TypeAdapter<?> mapped = null;
     if (annotation != null) {
+      // This is not safe; requires that user has specified correct adapter class for @JsonAdapter
       mapped = jsonAdapterFactory.getTypeAdapter(
           constructorConstructor, context, fieldType, annotation);
     }
@@ -138,7 +138,6 @@ private ReflectiveTypeAdapterFactory.BoundField createBoundField(
 
     final TypeAdapter<?> typeAdapter = mapped;
     return new ReflectiveTypeAdapterFactory.BoundField(name, serialize, deserialize) {
-      @SuppressWarnings({"unchecked", "rawtypes"}) // the type adapter and field type always agree
       @Override void write(JsonWriter writer, Object value)
           throws IOException, IllegalAccessException {
         if (!serialized) return;
@@ -152,7 +151,8 @@ private ReflectiveTypeAdapterFactory.BoundField createBoundField(
           return;
         }
         writer.name(name);
-        TypeAdapter t = jsonAdapterPresent ? typeAdapter
+        @SuppressWarnings({"unchecked", "rawtypes"})
+        TypeAdapter<Object> t = jsonAdapterPresent ? typeAdapter
             : new TypeAdapterRuntimeTypeWrapper(context, typeAdapter, fieldType.getType());
         t.write(writer, fieldValue);
       }

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

@@ -891,7 +891,6 @@ public EnumTypeAdapter(final Class<T> classOfT) {
   }
 
   public static final TypeAdapterFactory ENUM_FACTORY = new TypeAdapterFactory() {
-    @SuppressWarnings({"rawtypes", "unchecked"})
     @Override public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> typeToken) {
       Class<? super T> rawType = typeToken.getRawType();
       if (!Enum.class.isAssignableFrom(rawType) || rawType == Enum.class) {
@@ -900,7 +899,9 @@ public EnumTypeAdapter(final Class<T> classOfT) {
       if (!rawType.isEnum()) {
         rawType = rawType.getSuperclass(); // handle anonymous subclasses
       }
-      return (TypeAdapter<T>) new EnumTypeAdapter(rawType);
+      @SuppressWarnings({"rawtypes", "unchecked"})
+      TypeAdapter<T> adapter = (TypeAdapter<T>) new EnumTypeAdapter(rawType);
+      return adapter;
     }
   };
 

gson/src/test/java/com/google/gson/internal/JavaVersionTest.java

@@ -15,7 +15,8 @@
  */
 package com.google.gson.internal;
 
-import static org.junit.Assert.*;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
 
 import org.junit.Test;
 
@@ -29,7 +30,7 @@ public class JavaVersionTest {
 
   @Test
   public void testGetMajorJavaVersion() {
-    JavaVersion.getMajorJavaVersion();
+    assertTrue(JavaVersion.getMajorJavaVersion() >= 7); // Gson currently requires at least Java 7
   }
 
   @Test

pom.xml

@@ -73,7 +73,9 @@
             <showDeprecation>true</showDeprecation>
             <failOnWarning>true</failOnWarning>
             <compilerArgs>
-              <compilerArg>-Xlint:all</compilerArg>
+              <!-- Enable all warnings, except for ones which cause issues when building with newer JDKs, see also
+                https://docs.oracle.com/en/java/javase/11/tools/javac.html -->
+              <compilerArg>-Xlint:all,-options</compilerArg>
             </compilerArgs>
             <jdkToolchain>
               <version>[11,)</version>