Convert RequiredFieldsCheckOnReadTypeAdapterFactory to kotlin

app/src/main/java/fr/free/nrw/commons/wikidata/json/RequiredFieldsCheckOnReadTypeAdapterFactory.java

@@ -1,94 +0,0 @@
-package fr.free.nrw.commons.wikidata.json;
-
-import androidx.annotation.NonNull;
-import androidx.annotation.Nullable;
-import androidx.collection.ArraySet;
-
-import com.google.gson.Gson;
-import com.google.gson.JsonParseException;
-import com.google.gson.TypeAdapter;
-import com.google.gson.TypeAdapterFactory;
-import com.google.gson.reflect.TypeToken;
-import com.google.gson.stream.JsonReader;
-import com.google.gson.stream.JsonWriter;
-
-import fr.free.nrw.commons.wikidata.json.annotations.Required;
-
-import java.io.IOException;
-import java.lang.reflect.Field;
-import java.util.Collections;
-import java.util.Set;
-
-/**
- * TypeAdapterFactory that provides TypeAdapters that return null values for objects that are
- * missing fields annotated with @Required.
- *
- * BEWARE: This means that a List or other Collection of objects that have @Required fields can
- * contain null elements after deserialization!
- *
- * TODO: Handle null values in lists during deserialization, perhaps with a new @RequiredElements
- * annotation and another corresponding TypeAdapter(Factory).
- */
-public class RequiredFieldsCheckOnReadTypeAdapterFactory implements TypeAdapterFactory {
-    @Nullable @Override public final <T> TypeAdapter<T> create(@NonNull Gson gson, @NonNull TypeToken<T> typeToken) {
-        Class<?> rawType = typeToken.getRawType();
-        Set<Field> requiredFields = collectRequiredFields(rawType);
-
-        if (requiredFields.isEmpty()) {
-            return null;
-        }
-
-        setFieldsAccessible(requiredFields, true);
-        return new Adapter<>(gson.getDelegateAdapter(this, typeToken), requiredFields);
-    }
-
-    @NonNull private Set<Field> collectRequiredFields(@NonNull Class<?> clazz) {
-        Field[] fields = clazz.getDeclaredFields();
-        Set<Field> required = new ArraySet<>();
-        for (Field field : fields) {
-            if (field.isAnnotationPresent(Required.class)) {
-                required.add(field);
-            }
-        }
-        return Collections.unmodifiableSet(required);
-    }
-
-    private void setFieldsAccessible(Iterable<Field> fields, boolean accessible) {
-        for (Field field : fields) {
-            field.setAccessible(accessible);
-        }
-    }
-
-    private static final class Adapter<T> extends TypeAdapter<T> {
-        @NonNull private final TypeAdapter<T> delegate;
-        @NonNull private final Set<Field> requiredFields;
-
-        private Adapter(@NonNull TypeAdapter<T> delegate, @NonNull final Set<Field> requiredFields) {
-            this.delegate = delegate;
-            this.requiredFields = requiredFields;
-        }
-
-        @Override public void write(JsonWriter out, T value) throws IOException {
-            delegate.write(out, value);
-        }
-
-        @Override @Nullable public T read(JsonReader in) throws IOException {
-            T deserialized = delegate.read(in);
-            return allRequiredFieldsPresent(deserialized, requiredFields) ? deserialized : null;
-        }
-
-        private boolean allRequiredFieldsPresent(@NonNull T deserialized,
-                                                 @NonNull Set<Field> required) {
-            for (Field field : required) {
-                try {
-                    if (field.get(deserialized) == null) {
-                        return false;
-                    }
-                } catch (IllegalArgumentException | IllegalAccessException e) {
-                    throw new JsonParseException(e);
-                }
-            }
-            return true;
-        }
-    }
-}

app/src/main/java/fr/free/nrw/commons/wikidata/json/RequiredFieldsCheckOnReadTypeAdapterFactory.kt

@@ -0,0 +1,75 @@
+package fr.free.nrw.commons.wikidata.json
+
+import com.google.gson.Gson
+import com.google.gson.JsonParseException
+import com.google.gson.TypeAdapter
+import com.google.gson.TypeAdapterFactory
+import com.google.gson.reflect.TypeToken
+import com.google.gson.stream.JsonReader
+import com.google.gson.stream.JsonWriter
+import fr.free.nrw.commons.wikidata.json.annotations.Required
+import java.io.IOException
+import java.lang.reflect.Field
+
+/**
+ * TypeAdapterFactory that provides TypeAdapters that return null values for objects that are
+ * missing fields annotated with @Required.
+ *
+ * BEWARE: This means that a List or other Collection of objects that have @Required fields can
+ * contain null elements after deserialization!
+ *
+ * TODO: Handle null values in lists during deserialization, perhaps with a new @RequiredElements
+ * annotation and another corresponding TypeAdapter(Factory).
+ */
+class RequiredFieldsCheckOnReadTypeAdapterFactory : TypeAdapterFactory {
+    override fun <T> create(gson: Gson, typeToken: TypeToken<T>): TypeAdapter<T>? {
+        val rawType: Class<*> = typeToken.rawType
+        val requiredFields = collectRequiredFields(rawType)
+
+        if (requiredFields.isEmpty()) {
+            return null
+        }
+
+        for (field in requiredFields) {
+            field.isAccessible = true
+        }
+
+        return Adapter(gson.getDelegateAdapter(this, typeToken), requiredFields)
+    }
+
+    private fun collectRequiredFields(clazz: Class<*>): Set<Field> = buildSet {
+        for (field in clazz.declaredFields) {
+            if (field.isAnnotationPresent(Required::class.java)) add(field)
+        }
+    }
+
+    private class Adapter<T>(
+        private val delegate: TypeAdapter<T>,
+        private val requiredFields: Set<Field>
+    ) : TypeAdapter<T>() {
+
+        @Throws(IOException::class)
+        override fun write(out: JsonWriter, value: T?) =
+            delegate.write(out, value)
+
+        @Throws(IOException::class)
+        override fun read(reader: JsonReader): T? =
+            if (allRequiredFieldsPresent(delegate.read(reader), requiredFields))
+                delegate.read(reader)
+            else
+                null
+
+        fun allRequiredFieldsPresent(deserialized: T, required: Set<Field>): Boolean {
+            for (field in required) {
+                try {
+                    if (field[deserialized] == null) return false
+                } catch (e: IllegalArgumentException) {
+                    throw JsonParseException(e)
+                } catch (e: IllegalAccessException) {
+                    throw JsonParseException(e)
+                }
+            }
+            return true
+        }
+    }
+}

app/src/main/java/fr/free/nrw/commons/wikidata/json/annotations/Required.java

@@ -1,21 +0,0 @@
-package fr.free.nrw.commons.wikidata.json.annotations;
-
-
-import java.lang.annotation.Documented;
-import java.lang.annotation.Retention;
-import java.lang.annotation.RetentionPolicy;
-import java.lang.annotation.Target;
-
-import static java.lang.annotation.ElementType.FIELD;
-
-/**
- * Annotate fields in Retrofit POJO classes with this to enforce their presence in order to return
- * an instantiated object.
- *
- * E.g.: @NonNull @Required private String title;
- */
-@Documented
-@Retention(RetentionPolicy.RUNTIME)
-@Target(FIELD)
-public @interface Required {
-}

app/src/main/java/fr/free/nrw/commons/wikidata/json/annotations/Required.kt

@@ -0,0 +1,12 @@
+package fr.free.nrw.commons.wikidata.json.annotations
+
+
+/**
+ * Annotate fields in Retrofit POJO classes with this to enforce their presence in order to return
+ * an instantiated object.
+ *
+ * E.g.: @NonNull @Required private String title;
+ */
+@Retention(AnnotationRetention.RUNTIME)
+@Target(AnnotationTarget.FIELD)
+annotation class Required