Allow easy delegates in adapter methods. (#272)

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

@@ -55,8 +55,8 @@ final class AdapterMethodsFactory implements JsonAdapter.Factory {
       delegate = null;
     }
 
-    if (toAdapter != null) toAdapter.bind(moshi);
+    if (toAdapter != null) toAdapter.bind(moshi, this);
-    if (fromAdapter != null) fromAdapter.bind(moshi);
+    if (fromAdapter != null) fromAdapter.bind(moshi, this);
 
     return new JsonAdapter<Object>() {
       @Override public void toJson(JsonWriter writer, Object value) throws IOException {
@@ -170,8 +170,8 @@ final class AdapterMethodsFactory implements JsonAdapter.Factory {
           parameterTypes.length, 1, nullable) {
         private JsonAdapter<Object> delegate;
 
-        @Override public void bind(Moshi moshi) {
+        @Override public void bind(Moshi moshi, JsonAdapter.Factory factory) {
-          super.bind(moshi);
+          super.bind(moshi, factory);
           delegate = moshi.adapter(returnType, returnTypeAnnotations);
         }
 
@@ -235,8 +235,8 @@ final class AdapterMethodsFactory implements JsonAdapter.Factory {
           parameterTypes.length, 1, nullable) {
         JsonAdapter<Object> delegate;
 
-        @Override public void bind(Moshi moshi) {
+        @Override public void bind(Moshi moshi, JsonAdapter.Factory factory) {
-          super.bind(moshi);
+          super.bind(moshi, factory);
           delegate = moshi.adapter(parameterTypes[0], qualifierAnnotations);
         }
 
@@ -289,14 +289,17 @@ final class AdapterMethodsFactory implements JsonAdapter.Factory {
       this.nullable = nullable;
     }
 
-    public void bind(Moshi moshi) {
+    public void bind(Moshi moshi, JsonAdapter.Factory factory) {
       if (jsonAdapters.length > 0) {
         Type[] parameterTypes = method.getGenericParameterTypes();
         Annotation[][] parameterAnnotations = method.getParameterAnnotations();
         for (int i = adaptersOffset, size = parameterTypes.length; i < size; i++) {
-          jsonAdapters[i - adaptersOffset] = moshi.adapter(
+          Type type = ((ParameterizedType) parameterTypes[i]).getActualTypeArguments()[0];
-              ((ParameterizedType) parameterTypes[i]).getActualTypeArguments()[0],
+          Set<? extends Annotation> jsonAnnotations = jsonAnnotations(parameterAnnotations[i]);
-              jsonAnnotations(parameterAnnotations[i]));
+          jsonAdapters[i - adaptersOffset] =
+              Types.equals(this.type, type) && annotations.equals(jsonAnnotations)
+                  ? moshi.nextAdapter(factory, type, jsonAnnotations)
+                  : moshi.adapter(type, jsonAnnotations);
         }
       }
     }

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

@@ -79,6 +79,55 @@ public final class AdapterMethodsTest {
     }
   }
 
+  private static final class PointJsonAdapterWithDelegate {
+    @FromJson Point fromJson(JsonReader reader, JsonAdapter<Point> delegate) throws IOException {
+      reader.beginArray();
+      Point value = delegate.fromJson(reader);
+      reader.endArray();
+      return value;
+    }
+
+    @ToJson void toJson(JsonWriter writer, Point value, JsonAdapter<Point> delegate)
+        throws IOException {
+      writer.beginArray();
+      delegate.toJson(writer, value);
+      writer.endArray();
+    }
+  }
+
+  private static final class PointJsonAdapterWithDelegateWithQualifier {
+    @FromJson @WithParens Point fromJson(JsonReader reader, JsonAdapter<Point> delegate)
+        throws IOException {
+      reader.beginArray();
+      Point value = delegate.fromJson(reader);
+      reader.endArray();
+      return value;
+    }
+
+    @ToJson void toJson(JsonWriter writer, @WithParens Point value, JsonAdapter<Point> delegate)
+        throws IOException {
+      writer.beginArray();
+      delegate.toJson(writer, value);
+      writer.endArray();
+    }
+  }
+
+  @Test public void toAndFromWithDelegate() throws Exception {
+    Moshi moshi = new Moshi.Builder().add(new PointJsonAdapterWithDelegate()).build();
+    JsonAdapter<Point> adapter = moshi.adapter(Point.class);
+    Point point = new Point(5, 8);
+    assertThat(adapter.toJson(point)).isEqualTo("[{\"x\":5,\"y\":8}]");
+    assertThat(adapter.fromJson("[{\"x\":5,\"y\":8}]")).isEqualTo(point);
+  }
+
+  @Test public void toAndFromWithDelegateWithQualifier() throws Exception {
+    Moshi moshi = new Moshi.Builder().add(new PointJsonAdapterWithDelegateWithQualifier()).build();
+    JsonAdapter<Point> adapter = moshi.adapter(Point.class, WithParens.class);
+    Point point = new Point(5, 8);
+    assertThat(adapter.toJson(point)).isEqualTo("[{\"x\":5,\"y\":8}]");
+    assertThat(adapter.fromJson("[{\"x\":5,\"y\":8}]")).isEqualTo(point);
+  }
+
   @Test public void toJsonOnly() throws Exception {
     Moshi moshi = new Moshi.Builder()
         .add(new PointAsListOfIntegersToAdapter())
@@ -308,7 +357,7 @@ public final class AdapterMethodsTest {
   }
 
   static class NullableIntToJsonAdapter {
-    @FromJson int intToJson(JsonReader reader) throws IOException {
+    @FromJson int jsonToInt(JsonReader reader) throws IOException {
       if (reader.peek() == JsonReader.Token.NULL) {
         reader.nextNull();
         return -1;
@@ -316,7 +365,7 @@ public final class AdapterMethodsTest {
       return reader.nextInt();
     }
 
-    @ToJson void jsonToInt(JsonWriter writer, int value) throws IOException {
+    @ToJson void intToJson(JsonWriter writer, int value) throws IOException {
       if (value == -1) {
         writer.nullValue();
       } else {