Merge pull request #48 from square/jwilson_0601_nullable

Support @Nullable in Adapter Methods.

moshi/src/main/java/com/squareup/moshi/AdapterMethodsFactory.java

@@ -50,6 +50,8 @@ final class AdapterMethodsFactory implements JsonAdapter.Factory {
       @Override public void toJson(JsonWriter writer, Object value) throws IOException {
         if (toAdapter == null) {
           delegate.toJson(writer, value);
+        } else if (!toAdapter.nullable && value == null) {
+          writer.nullValue();
         } else {
           try {
             toAdapter.toJson(moshi, writer, value);
@@ -65,6 +67,9 @@ final class AdapterMethodsFactory implements JsonAdapter.Factory {
       @Override public Object fromJson(JsonReader reader) throws IOException {
         if (fromAdapter == null) {
           return delegate.fromJson(reader);
+        } else if (!fromAdapter.nullable && reader.peek() == JsonReader.Token.NULL) {
+          reader.nextNull();
+          return null;
         } else {
           try {
             return fromAdapter.fromJson(moshi, reader);
@@ -132,7 +137,7 @@ final class AdapterMethodsFactory implements JsonAdapter.Factory {
       // public void pointToJson(JsonWriter jsonWriter, Point point) throws Exception {
       Set<? extends Annotation> parameterAnnotations
           = Util.jsonAnnotations(method.getParameterAnnotations()[1]);
-      return new AdapterMethod(parameterTypes[1], parameterAnnotations, adapter, method) {
+      return new AdapterMethod(parameterTypes[1], parameterAnnotations, adapter, method, false) {
         @Override public void toJson(Moshi moshi, JsonWriter writer, Object value)
             throws IOException, InvocationTargetException, IllegalAccessException {
           method.invoke(adapter, writer, value);
@@ -142,9 +147,11 @@ final class AdapterMethodsFactory implements JsonAdapter.Factory {
     } else if (parameterTypes.length == 1 && returnType != void.class) {
       // public List<Integer> pointToJson(Point point) throws Exception {
       final Set<? extends Annotation> returnTypeAnnotations = Util.jsonAnnotations(method);
-      Set<? extends Annotation> parameterAnnotations =
+      Annotation[][] parameterAnnotations = method.getParameterAnnotations();
-          Util.jsonAnnotations(method.getParameterAnnotations()[0]);
+      Set<? extends Annotation> qualifierAnnotations =
-      return new AdapterMethod(parameterTypes[0], parameterAnnotations, adapter, method) {
+          Util.jsonAnnotations(parameterAnnotations[0]);
+      boolean nullable = Util.hasNullable(parameterAnnotations[0]);
+      return new AdapterMethod(parameterTypes[0], qualifierAnnotations, adapter, method, nullable) {
         @Override public void toJson(Moshi moshi, JsonWriter writer, Object value)
             throws IOException, InvocationTargetException, IllegalAccessException {
           JsonAdapter<Object> delegate = moshi.adapter(returnType, returnTypeAnnotations);
@@ -175,7 +182,7 @@ final class AdapterMethodsFactory implements JsonAdapter.Factory {
         && returnType != void.class) {
       // public Point pointFromJson(JsonReader jsonReader) throws Exception {
       Set<? extends Annotation> returnTypeAnnotations = Util.jsonAnnotations(method);
-      return new AdapterMethod(returnType, returnTypeAnnotations, adapter, method) {
+      return new AdapterMethod(returnType, returnTypeAnnotations, adapter, method, false) {
         @Override public Object fromJson(Moshi moshi, JsonReader reader)
             throws IOException, IllegalAccessException, InvocationTargetException {
           return method.invoke(adapter, reader);
@@ -185,12 +192,14 @@ final class AdapterMethodsFactory implements JsonAdapter.Factory {
     } else if (parameterTypes.length == 1 && returnType != void.class) {
       // public Point pointFromJson(List<Integer> o) throws Exception {
       Set<? extends Annotation> returnTypeAnnotations = Util.jsonAnnotations(method);
-      final Set<? extends Annotation> parameterAnnotations
+      Annotation[][] parameterAnnotations = method.getParameterAnnotations();
-          = Util.jsonAnnotations(method.getParameterAnnotations()[0]);
+      final Set<? extends Annotation> qualifierAnnotations
-      return new AdapterMethod(returnType, returnTypeAnnotations, adapter, method) {
+          = Util.jsonAnnotations(parameterAnnotations[0]);
+      boolean nullable = Util.hasNullable(parameterAnnotations[0]);
+      return new AdapterMethod(returnType, returnTypeAnnotations, adapter, method, nullable) {
         @Override public Object fromJson(Moshi moshi, JsonReader reader)
             throws IOException, IllegalAccessException, InvocationTargetException {
-          JsonAdapter<Object> delegate = moshi.adapter(parameterTypes[0], parameterAnnotations);
+          JsonAdapter<Object> delegate = moshi.adapter(parameterTypes[0], qualifierAnnotations);
           Object intermediate = delegate.fromJson(reader);
           return method.invoke(adapter, intermediate);
         }
@@ -221,13 +230,15 @@ final class AdapterMethodsFactory implements JsonAdapter.Factory {
     final Set<? extends Annotation> annotations;
     final Object adapter;
     final Method method;
+    final boolean nullable;
 
     public AdapterMethod(Type type,
-        Set<? extends Annotation> annotations, Object adapter, Method method) {
+        Set<? extends Annotation> annotations, Object adapter, Method method, boolean nullable) {
       this.type = type;
       this.annotations = annotations;
       this.adapter = adapter;
       this.method = method;
+      this.nullable = nullable;
     }
 
     public void toJson(Moshi moshi, JsonWriter writer, Object value)

moshi/src/main/java/com/squareup/moshi/Util.java

@@ -53,4 +53,14 @@ final class Util {
     }
     return false;
   }
+
+  /** Returns true if {@code annotations} has any annotation whose simple name is Nullable. */
+  public static boolean hasNullable(Annotation[] annotations) {
+    for (Annotation annotation : annotations) {
+      if (annotation.annotationType().getSimpleName().equals("Nullable")) {
+        return true;
+      }
+    }
+    return false;
+  }
 }

moshi/src/test/java/com/squareup/moshi/AdapterMethodsTest.java

@@ -16,6 +16,8 @@
 package com.squareup.moshi;
 
 import java.io.IOException;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
@@ -181,6 +183,56 @@ public final class AdapterMethodsTest {
     }
   }
 
+  /**
+   * Simple adapter methods are not invoked for null values unless they're annotated {@code
+   * @Nullable}. (The specific annotation class doesn't matter; just its simple name.)
+   */
+  @Test public void toAndFromNullNotNullable() throws Exception {
+    Moshi moshi = new Moshi.Builder()
+        .add(new NotNullablePointAsListOfIntegersJsonAdapter())
+        .build();
+    JsonAdapter<Point> pointAdapter = moshi.adapter(Point.class).lenient();
+    assertThat(pointAdapter.toJson(null)).isEqualTo("null");
+    assertThat(pointAdapter.fromJson("null")).isNull();
+  }
+
+  static class NotNullablePointAsListOfIntegersJsonAdapter {
+    @ToJson List<Integer> pointToJson(Point point) {
+      throw new AssertionError();
+    }
+
+    @FromJson Point pointFromJson(List<Integer> o) throws Exception {
+      throw new AssertionError();
+    }
+  }
+
+  @Test public void toAndFromNullNullable() throws Exception {
+    Moshi moshi = new Moshi.Builder()
+        .add(new NullablePointAsListOfIntegersJsonAdapter())
+        .build();
+    JsonAdapter<Point> pointAdapter = moshi.adapter(Point.class).lenient();
+    assertThat(pointAdapter.toJson(null)).isEqualTo("[0,0]");
+    assertThat(pointAdapter.fromJson("null")).isEqualTo(new Point(0, 0));
+  }
+
+  static class NullablePointAsListOfIntegersJsonAdapter {
+    @ToJson List<Integer> pointToJson(@Nullable Point point) {
+      return point != null
+          ? Arrays.asList(point.x, point.y)
+          : Arrays.asList(0, 0);
+    }
+
+    @FromJson Point pointFromJson(@Nullable List<Integer> o) throws Exception {
+      if (o == null) return new Point(0, 0);
+      if (o.size() == 2) return new Point(o.get(0), o.get(1));
+      throw new Exception("Expected null or 2 elements but was " + o);
+    }
+  }
+
+  @Retention(RetentionPolicy.RUNTIME)
+  @interface Nullable {
+  }
+
   static class Point {
     final int x;
     final int y;