mark JsonTypeCoercer.coerce as nullable

de-facto it can return null. Now IDEA will know it, and show warning for unsafe usages.

Author: asolntsev

java/src/org/openqa/selenium/json/CollectionCoercer.java

@@ -24,20 +24,21 @@
 import java.util.function.Consumer;
 import java.util.function.Function;
 import java.util.function.Supplier;
+import org.jspecify.annotations.Nullable;
 import org.openqa.selenium.internal.Require;
 
-class CollectionCoercer<T extends Collection, I extends T> extends TypeCoercer<T> {
+class CollectionCoercer<T extends Collection<?>, I extends T> extends TypeCoercer<T> {
 
   private final Class<T> stereotype;
   private final JsonTypeCoercer coercer;
   private final Supplier<I> supplier;
-  private final Function<I, Consumer<Object>> consumerFactory;
+  private final Function<I, Consumer<@Nullable Object>> consumerFactory;
 
   public CollectionCoercer(
       Class<T> stereotype,
       JsonTypeCoercer coercer,
       Supplier<I> supplier,
-      Function<I, Consumer<Object>> consumerFactory) {
+      Function<I, Consumer<@Nullable Object>> consumerFactory) {
     this.stereotype = Require.nonNull("Stereotype", stereotype);
     this.coercer = Require.nonNull("Coercer", coercer);
     this.supplier = Require.nonNull("Supplier", supplier);
@@ -65,7 +66,7 @@ public BiFunction<JsonInput, PropertySetting, T> apply(Type type) {
     return (jsonInput, setting) -> {
       jsonInput.beginArray();
       I toReturn = supplier.get();
-      Consumer<Object> consumer = consumerFactory.apply(toReturn);
+      Consumer<@Nullable Object> consumer = consumerFactory.apply(toReturn);
       while (jsonInput.hasNext()) {
         consumer.accept(coercer.coerce(jsonInput, valueType, setting));
       }

java/src/org/openqa/selenium/json/ConstructorCoercer.java

@@ -36,6 +36,7 @@
 import java.util.Set;
 import java.util.function.BiFunction;
 import java.util.stream.Stream;
+import org.jspecify.annotations.Nullable;
 import org.openqa.selenium.internal.Require;
 
 class ConstructorCoercer extends TypeCoercer<Object> {
@@ -147,6 +148,7 @@ private Map<String, Integer> getParameterIndexes(Parameter[] parameters) {
     return indexes;
   }
 
+  @Nullable
   private Object coerceValue(Object value, Type type, PropertySetting setting) {
     StringWriter rawJson = new StringWriter();
     try (JsonOutput output = new JsonOutput(rawJson)) {

java/src/org/openqa/selenium/json/EnumCoercer.java

@@ -22,7 +22,7 @@
 import java.lang.reflect.Type;
 import java.util.function.BiFunction;
 
-public class EnumCoercer<T extends Enum> extends TypeCoercer<T> {
+public class EnumCoercer<T extends Enum<T>> extends TypeCoercer<T> {
 
   @Override
   public boolean test(Class<?> aClass) {

java/src/org/openqa/selenium/json/InstanceCoercer.java

@@ -32,6 +32,7 @@
 import java.util.function.BiFunction;
 import java.util.function.Function;
 import java.util.stream.Stream;
+import org.jspecify.annotations.Nullable;
 import org.openqa.selenium.internal.Require;
 
 class InstanceCoercer extends TypeCoercer<Object> {
@@ -168,9 +169,9 @@ private static Class<?> getClss(Type type) {
 
   private static class TypeAndWriter {
     private final Type type;
-    private final BiConsumer<Object, Object> writer;
+    private final BiConsumer<Object, @Nullable Object> writer;
 
-    TypeAndWriter(Type type, BiConsumer<Object, Object> writer) {
+    TypeAndWriter(Type type, BiConsumer<Object, @Nullable Object> writer) {
       this.type = type;
       this.writer = writer;
     }
@@ -189,15 +190,15 @@ public TypeAndWriter apply(Field field) {
     }
   }
 
-  private static class FieldWriter implements BiConsumer<Object, Object> {
+  private static class FieldWriter implements BiConsumer<Object, @Nullable Object> {
     private final Field field;
 
     FieldWriter(Field field) {
       this.field = field;
     }
 
     @Override
-    public void accept(Object instance, Object value) {
+    public void accept(Object instance, @Nullable Object value) {
       try {
         field.set(instance, value);
       } catch (IllegalAccessException e) {
@@ -226,7 +227,7 @@ public TypeAndWriter apply(SimplePropertyDescriptor desc) {
     }
   }
 
-  private static class SimplePropertyWriter implements BiConsumer<Object, Object> {
+  private static class SimplePropertyWriter implements BiConsumer<Object, @Nullable Object> {
     private final SimplePropertyDescriptor desc;
     private final Method method;
 
@@ -236,7 +237,7 @@ private static class SimplePropertyWriter implements BiConsumer<Object, Object>
     }
 
     @Override
-    public void accept(Object instance, Object value) {
+    public void accept(Object instance, @Nullable Object value) {
       method.setAccessible(true);
       try {
         method.invoke(instance, value);

java/src/org/openqa/selenium/json/JsonInput.java

@@ -540,8 +540,8 @@ public <T> T readMapElement(String key) {
    * @throws JsonException if coercion of the next element to the specified type fails
    * @throws UncheckedIOException if an I/O exception is encountered
    */
-  public <T> List<T> readArray(Type type) {
-    List<T> toReturn = new ArrayList<>();
+  public <T> List<@Nullable T> readArray(Type type) {
+    List<@Nullable T> toReturn = new ArrayList<>();
 
     beginArray();
     while (hasNext()) {

java/src/org/openqa/selenium/json/JsonTypeCoercer.java

@@ -37,6 +37,7 @@
 import java.util.function.BiFunction;
 import java.util.stream.Stream;
 import java.util.stream.StreamSupport;
+import org.jspecify.annotations.Nullable;
 import org.openqa.selenium.Capabilities;
 import org.openqa.selenium.MutableCapabilities;
 import org.openqa.selenium.internal.Require;
@@ -113,11 +114,8 @@ private JsonTypeCoercer(Stream<TypeCoercer<?>> coercers) {
             (caps) -> ((k, v) -> caps.setCapability((String) k, v))));
 
     // Container types
-    //noinspection unchecked
     builder.add(new CollectionCoercer<>(List.class, this, ArrayList::new, (list) -> list::add));
-    //noinspection unchecked
     builder.add(new CollectionCoercer<>(Set.class, this, HashSet::new, (set) -> set::add));
-    //noinspection unchecked
     builder.add(
         new CollectionCoercer<>(
             Collection.class, this, ArrayList::new, (collection) -> collection::add));
@@ -139,7 +137,7 @@ private JsonTypeCoercer(Stream<TypeCoercer<?>> coercers) {
     this.coercers = Collections.unmodifiableSet(builder);
   }
 
-  <T> T coerce(JsonInput json, Type typeOfT, PropertySetting setter) {
+  @Nullable <T> T coerce(JsonInput json, Type typeOfT, PropertySetting setter) {
     BiFunction<JsonInput, PropertySetting, Object> coercer =
         knownCoercers.computeIfAbsent(typeOfT, this::buildCoercer);
 

java/src/org/openqa/selenium/json/MapCoercer.java

@@ -17,25 +17,28 @@
 
 package org.openqa.selenium.json;
 
+import static java.util.Objects.requireNonNull;
+
 import java.lang.reflect.ParameterizedType;
 import java.lang.reflect.Type;
 import java.util.function.BiConsumer;
 import java.util.function.BiFunction;
 import java.util.function.Function;
 import java.util.function.Supplier;
+import org.jspecify.annotations.Nullable;
 
 class MapCoercer<T, I extends T> extends TypeCoercer<T> {
 
   private final Class<T> stereotype;
   private final JsonTypeCoercer coercer;
   private final Supplier<I> supplier;
-  private final Function<I, BiConsumer<Object, Object>> consumerFactory;
+  private final Function<I, BiConsumer<Object, @Nullable Object>> consumerFactory;
 
   public MapCoercer(
       Class<T> stereotype,
       JsonTypeCoercer coercer,
       Supplier<I> supplier,
-      Function<I, BiConsumer<Object, Object>> consumerFactory) {
+      Function<I, BiConsumer<Object, @Nullable Object>> consumerFactory) {
     this.stereotype = stereotype;
     this.coercer = coercer;
     this.supplier = supplier;
@@ -66,7 +69,7 @@ public BiFunction<JsonInput, PropertySetting, T> apply(Type type) {
     return (jsonInput, setting) -> {
       jsonInput.beginObject();
       I toReturn = supplier.get();
-      BiConsumer<Object, Object> consumer = consumerFactory.apply(toReturn);
+      BiConsumer<Object, @Nullable Object> consumer = consumerFactory.apply(toReturn);
       // JSON should always have a string key, so we can take the fastpath
       boolean stringKey = String.class.equals(keyType);
 
@@ -76,7 +79,7 @@ public BiFunction<JsonInput, PropertySetting, T> apply(Type type) {
         if (stringKey) {
           key = jsonInput.nextName();
         } else {
-          key = coercer.coerce(jsonInput, keyType, setting);
+          key = requireNonNull(coercer.coerce(jsonInput, keyType, setting));
         }
         Object value = coercer.coerce(jsonInput, valueType, setting);
 

java/src/org/openqa/selenium/json/ObjectCoercer.java

@@ -20,6 +20,7 @@
 import java.lang.reflect.Type;
 import java.util.List;
 import java.util.function.BiFunction;
+import org.jspecify.annotations.Nullable;
 import org.openqa.selenium.internal.Require;
 
 class ObjectCoercer extends TypeCoercer<Object> {
@@ -36,7 +37,7 @@ public boolean test(Class type) {
   }
 
   @Override
-  public BiFunction<JsonInput, PropertySetting, Object> apply(Type type) {
+  public BiFunction<JsonInput, PropertySetting, @Nullable Object> apply(Type type) {
     return (jsonInput, setting) -> {
       Type target;
 

java/src/org/openqa/selenium/json/TypeCoercer.java

@@ -21,6 +21,7 @@
 import java.util.function.BiFunction;
 import java.util.function.Function;
 import java.util.function.Predicate;
+import org.jspecify.annotations.Nullable;
 
 public abstract class TypeCoercer<T>
     implements Predicate<Class<?>>, Function<Type, BiFunction<JsonInput, PropertySetting, T>> {
@@ -29,5 +30,5 @@ public abstract class TypeCoercer<T>
   public abstract boolean test(Class<?> aClass);
 
   @Override
-  public abstract BiFunction<JsonInput, PropertySetting, T> apply(Type type);
+  public abstract BiFunction<JsonInput, PropertySetting, @Nullable T> apply(Type type);
 }

java/test/org/openqa/selenium/json/JsonInputTest.java

@@ -234,7 +234,7 @@ void shouldDecodeUnicodeEscapesProperly() {
     String raw = "{\"text\": \"\\u003Chtml\"}";
 
     try (JsonInput in = new JsonInput(new StringReader(raw), new JsonTypeCoercer(), BY_NAME)) {
-      Map<String, Object> map = in.read(MAP_TYPE);
+      Map<String, Object> map = in.readMap();
 
       assertThat(map.get("text")).isEqualTo("<html");
     }
@@ -245,7 +245,8 @@ void shouldCallFromJsonWithJsonInputParameter() {
     String raw = "{\"message\": \"Cheese!\"}";
 
     try (JsonInput in = new JsonInput(new StringReader(raw), new JsonTypeCoercer(), BY_NAME)) {
-      HasFromJsonWithJsonInputParameter obj = in.read(HasFromJsonWithJsonInputParameter.class);
+      HasFromJsonWithJsonInputParameter obj =
+          in.readNonNull(HasFromJsonWithJsonInputParameter.class);
 
       assertThat(obj.getMessage()).isEqualTo("Cheese!");
     }
@@ -262,6 +263,17 @@ void canReadListOfType() {
     }
   }
 
+  @Test
+  void canReadListOfType_null() {
+    String raw = "[null, null]";
+
+    try (JsonInput in = new JsonInput(new StringReader(raw), new JsonTypeCoercer(), BY_NAME)) {
+      List<Integer> array = in.readArray(Integer.class);
+
+      assertThat(array).containsExactly(null, null);
+    }
+  }
+
   @Test
   void shouldBeAbleToReadDataLongerThanReadBuffer() {
     char[] chars = new char[] {'c', 'h', 'e', 's'};