Full JsonQualifier support in kotlin codegen.

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

@@ -20,6 +20,7 @@ import com.squareup.moshi.internal.Util.ParameterizedTypeImpl;
 import com.squareup.moshi.internal.Util.WildcardTypeImpl;
 import java.lang.annotation.Annotation;
 import java.lang.reflect.Array;
+import java.lang.reflect.Field;
 import java.lang.reflect.GenericArrayType;
 import java.lang.reflect.InvocationHandler;
 import java.lang.reflect.Method;
@@ -216,6 +217,36 @@ public final class Types {
     }
   }
 
+  /**
+   * @param clazz the target class to read the {@code fieldName} field annotations from.
+   * @param fieldName the target field name on {@code clazz}.
+   * @return a set of {@link JsonQualifier}-annotated {@link Annotation} instances retrieved from
+   *         the targeted field. Can be empty if none are found.
+   */
+  public static Set<? extends Annotation> getFieldJsonQualifierAnnotations(Class<?> clazz,
+      String fieldName) {
+    try {
+      Field field = clazz.getDeclaredField(fieldName);
+      if (!field.isAccessible()) {
+        field.setAccessible(true);
+      }
+      Annotation[] fieldAnnotations = field.getDeclaredAnnotations();
+      Set<Annotation> annotations = new LinkedHashSet<>(fieldAnnotations.length);
+      for (Annotation annotation : fieldAnnotations) {
+        if (annotation.annotationType().isAnnotationPresent(JsonQualifier.class)) {
+          annotations.add(annotation);
+        }
+      }
+      return Collections.unmodifiableSet(annotations);
+    } catch (NoSuchFieldException e) {
+      throw new IllegalArgumentException("Could not access field "
+          + fieldName
+          + " on class "
+          + clazz.getCanonicalName(),
+          e);
+    }
+  }
+
   @SuppressWarnings("unchecked")
   static <T extends Annotation> T createJsonQualifierImplementation(final Class<T> annotationType) {
     if (!annotationType.isAnnotation()) {

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

@@ -17,6 +17,7 @@ package com.squareup.moshi;
 
 import java.lang.annotation.Annotation;
 import java.lang.annotation.Retention;
+import java.lang.annotation.Target;
 import java.lang.reflect.ParameterizedType;
 import java.lang.reflect.Type;
 import java.util.ArrayList;
@@ -29,6 +30,7 @@ import java.util.Set;
 import org.junit.Test;
 
 import static com.squareup.moshi.internal.Util.canonicalize;
+import static java.lang.annotation.ElementType.FIELD;
 import static java.lang.annotation.RetentionPolicy.RUNTIME;
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.Assert.fail;
@@ -261,4 +263,52 @@ public final class TypesTest {
       assertThat(expected).hasMessage("Unexpected primitive boolean. Use the boxed type.");
     }
   }
+
+  @Test public void getFieldJsonQualifierAnnotations_privateFieldTest() {
+    Set<? extends Annotation> annotations = Types.getFieldJsonQualifierAnnotations(ClassWithAnnotatedFields.class,
+        "privateField");
+
+    assertThat(annotations).hasSize(1);
+    assertThat(annotations.iterator().next()).isInstanceOf(FieldAnnotation.class);
+  }
+
+  @Test public void getFieldJsonQualifierAnnotations_publicFieldTest() {
+    Set<? extends Annotation> annotations = Types.getFieldJsonQualifierAnnotations(ClassWithAnnotatedFields.class,
+        "publicField");
+
+    assertThat(annotations).hasSize(1);
+    assertThat(annotations.iterator().next()).isInstanceOf(FieldAnnotation.class);
+  }
+
+  @Test public void getFieldJsonQualifierAnnotations_unannotatedTest() {
+    Set<? extends Annotation> annotations = Types.getFieldJsonQualifierAnnotations(ClassWithAnnotatedFields.class,
+        "unannotatedField");
+
+    assertThat(annotations).hasSize(0);
+  }
+
+  @JsonQualifier
+  @Target(FIELD)
+  @Retention(RUNTIME)
+  @interface FieldAnnotation {
+
+  }
+
+  @Target(FIELD)
+  @Retention(RUNTIME)
+  @interface NoQualifierAnnotation {
+
+  }
+
+  static class ClassWithAnnotatedFields {
+    @FieldAnnotation
+    @NoQualifierAnnotation
+    private final int privateField = 0;
+
+    @FieldAnnotation
+    @NoQualifierAnnotation
+    public final int publicField = 0;
+
+    private final int unannotatedField = 0;
+  }
 }