Convert MapJsonAdapter to Kotlin (#1492)

* Rename .java to .kt

* Convert MapJsonAdapter to Kotlin

* Pull up factory into companion object

* Spotless

* apicmp

* Use knownNotNull

* Use a template

moshi/japicmp/build.gradle.kts

@@ -35,7 +35,8 @@ val japicmp = tasks.register<JapicmpTask>("japicmp") {
     "com.squareup.moshi.JsonAdapter#indent(java.lang.String)" // Was unintentionally open before
   )
   fieldExcludes = listOf(
-    "com.squareup.moshi.CollectionJsonAdapter#FACTORY" // False-positive, class is not public anyway
+    "com.squareup.moshi.CollectionJsonAdapter#FACTORY", // False-positive, class is not public anyway
+    "com.squareup.moshi.MapJsonAdapter#FACTORY" // Class is not public
   )
 }
 

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

@@ -26,6 +26,7 @@ import java.util.Iterator;
 import java.util.LinkedHashMap;
 import java.util.NoSuchElementException;
 import java.util.Set;
+import javax.annotation.Nullable;
 
 /**
  * A map of comparable keys to values. Unlike {@code TreeMap}, this class uses insertion order for
@@ -90,7 +91,7 @@ final class LinkedHashTreeMap<K, V> extends AbstractMap<K, V> implements Seriali
   }
 
   @Override
-  public V put(K key, V value) {
+  public V put(K key, @Nullable V value) {
     if (key == null) {
       throw new NullPointerException("key == null");
     }

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

@@ -1,95 +0,0 @@
-/*
- * Copyright (C) 2015 Square, Inc.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *    https://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package com.squareup.moshi;
-
-import java.io.IOException;
-import java.lang.annotation.Annotation;
-import java.lang.reflect.Type;
-import java.util.Map;
-import java.util.Set;
-import javax.annotation.Nullable;
-
-/**
- * Converts maps with string keys to JSON objects.
- *
- * <p>TODO: support maps with other key types and convert to/from strings.
- */
-final class MapJsonAdapter<K, V> extends JsonAdapter<Map<K, V>> {
-  public static final Factory FACTORY =
-      new Factory() {
-        @Override
-        public @Nullable JsonAdapter<?> create(
-            Type type, Set<? extends Annotation> annotations, Moshi moshi) {
-          if (!annotations.isEmpty()) return null;
-          Class<?> rawType = Types.getRawType(type);
-          if (rawType != Map.class) return null;
-          Type[] keyAndValue = Types.mapKeyAndValueTypes(type, rawType);
-          return new MapJsonAdapter<>(moshi, keyAndValue[0], keyAndValue[1]).nullSafe();
-        }
-      };
-
-  private final JsonAdapter<K> keyAdapter;
-  private final JsonAdapter<V> valueAdapter;
-
-  MapJsonAdapter(Moshi moshi, Type keyType, Type valueType) {
-    this.keyAdapter = moshi.adapter(keyType);
-    this.valueAdapter = moshi.adapter(valueType);
-  }
-
-  @Override
-  public void toJson(JsonWriter writer, Map<K, V> map) throws IOException {
-    writer.beginObject();
-    for (Map.Entry<K, V> entry : map.entrySet()) {
-      if (entry.getKey() == null) {
-        throw new JsonDataException("Map key is null at " + writer.getPath());
-      }
-      writer.promoteValueToName();
-      keyAdapter.toJson(writer, entry.getKey());
-      valueAdapter.toJson(writer, entry.getValue());
-    }
-    writer.endObject();
-  }
-
-  @Override
-  public Map<K, V> fromJson(JsonReader reader) throws IOException {
-    LinkedHashTreeMap<K, V> result = new LinkedHashTreeMap<>();
-    reader.beginObject();
-    while (reader.hasNext()) {
-      reader.promoteNameToValue();
-      K name = keyAdapter.fromJson(reader);
-      V value = valueAdapter.fromJson(reader);
-      V replaced = result.put(name, value);
-      if (replaced != null) {
-        throw new JsonDataException(
-            "Map key '"
-                + name
-                + "' has multiple values at path "
-                + reader.getPath()
-                + ": "
-                + replaced
-                + " and "
-                + value);
-      }
-    }
-    reader.endObject();
-    return result;
-  }
-
-  @Override
-  public String toString() {
-    return "JsonAdapter(" + keyAdapter + "=" + valueAdapter + ")";
-  }
-}

moshi/src/main/java/com/squareup/moshi/MapJsonAdapter.kt

@@ -0,0 +1,73 @@
+/*
+ * Copyright (C) 2015 Square, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.squareup.moshi
+
+import com.squareup.moshi.internal.knownNotNull
+import java.lang.reflect.Type
+
+/**
+ * Converts maps with string keys to JSON objects.
+ *
+ * TODO: support maps with other key types and convert to/from strings.
+ */
+internal class MapJsonAdapter<K, V>(moshi: Moshi, keyType: Type, valueType: Type) : JsonAdapter<Map<K, V?>>() {
+  private val keyAdapter: JsonAdapter<K> = moshi.adapter(keyType)
+  private val valueAdapter: JsonAdapter<V> = moshi.adapter(valueType)
+
+  override fun toJson(writer: JsonWriter, map: Map<K, V?>?) {
+    writer.beginObject()
+    // Never null because we wrap in nullSafe()
+    for ((key, value) in knownNotNull(map)) {
+      if (key == null) {
+        throw JsonDataException("Map key is null at " + writer.path)
+      }
+      writer.promoteValueToName()
+      keyAdapter.toJson(writer, key)
+      valueAdapter.toJson(writer, value)
+    }
+    writer.endObject()
+  }
+
+  override fun fromJson(reader: JsonReader): Map<K, V?> {
+    val result = LinkedHashTreeMap<K, V?>()
+    reader.beginObject()
+    while (reader.hasNext()) {
+      reader.promoteNameToValue()
+      val name = keyAdapter.fromJson(reader) ?: throw JsonDataException("Map key is null at ${reader.path}")
+      val value = valueAdapter.fromJson(reader)
+      val replaced = result.put(name, value)
+      if (replaced != null) {
+        throw JsonDataException(
+          "Map key '$name' has multiple values at path ${reader.path}: $replaced and $value"
+        )
+      }
+    }
+    reader.endObject()
+    return result
+  }
+
+  override fun toString() = "JsonAdapter($keyAdapter=$valueAdapter)"
+
+  companion object Factory : JsonAdapter.Factory {
+    override fun create(type: Type, annotations: Set<Annotation>, moshi: Moshi): JsonAdapter<*>? {
+      if (annotations.isNotEmpty()) return null
+      val rawType = type.rawType
+      if (rawType != Map::class.java) return null
+      val keyAndValue = Types.mapKeyAndValueTypes(type, rawType)
+      return MapJsonAdapter<Any, Any>(moshi, keyAndValue[0], keyAndValue[1]).nullSafe()
+    }
+  }
+}

moshi/src/main/java/com/squareup/moshi/Moshi.kt

@@ -366,7 +366,7 @@ public class Moshi internal constructor(builder: Builder) {
     val BUILT_IN_FACTORIES: List<JsonAdapter.Factory> = buildList(6) {
       add(StandardJsonAdapters)
       add(CollectionJsonAdapter.Factory)
-      add(MapJsonAdapter.FACTORY)
+      add(MapJsonAdapter.Factory)
       add(ArrayJsonAdapter.FACTORY)
       add(RecordJsonAdapter.FACTORY)
       add(ClassJsonAdapter.FACTORY)

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

@@ -262,7 +262,7 @@ public final class MapJsonAdapterTest {
   @SuppressWarnings("unchecked") // It's the caller's responsibility to make sure K and V match.
   private <K, V> JsonAdapter<Map<K, V>> mapAdapter(Type keyType, Type valueType) {
     return (JsonAdapter<Map<K, V>>)
-        MapJsonAdapter.FACTORY.create(
+        MapJsonAdapter.Factory.create(
             Types.newParameterizedType(Map.class, keyType, valueType), NO_ANNOTATIONS, moshi);
   }