fix: add support to deserialize to custom Lists and Maps (#337)

google-cloud-firestore/src/main/java/com/google/cloud/firestore/CustomClassMapper.java

@@ -266,7 +266,21 @@ private static <T> T deserializeToParameterizedType(
       Type genericType = type.getActualTypeArguments()[0];
       if (o instanceof List) {
         List<Object> list = (List<Object>) o;
-        List<Object> result = new ArrayList<>(list.size());
+        List<Object> result;
+        try {
+          result =
+              (rawType == List.class)
+                  ? new ArrayList<>(list.size())
+                  : (List<Object>) rawType.getDeclaredConstructor().newInstance();
+        } catch (InstantiationException
+            | IllegalAccessException
+            | NoSuchMethodException
+            | InvocationTargetException e) {
+          throw deserializeError(
+              context.errorPath,
+              String.format(
+                  "Unable to deserialize to %s: %s", rawType.getSimpleName(), e.toString()));
+        }
         for (int i = 0; i < list.size(); i++) {
           result.add(
               deserializeToType(
@@ -287,7 +301,21 @@ private static <T> T deserializeToParameterizedType(
             "Only Maps with string keys are supported, but found Map with key type " + keyType);
       }
       Map<String, Object> map = expectMap(o, context);
-      HashMap<String, Object> result = new HashMap<>();
+      HashMap<String, Object> result;
+      try {
+        result =
+            (rawType == Map.class)
+                ? new HashMap<String, Object>()
+                : (HashMap<String, Object>) rawType.getDeclaredConstructor().newInstance();
+      } catch (InstantiationException
+          | IllegalAccessException
+          | NoSuchMethodException
+          | InvocationTargetException e) {
+        throw deserializeError(
+            context.errorPath,
+            String.format(
+                "Unable to deserialize to %s: %s", rawType.getSimpleName(), e.toString()));
+      }
       for (Map.Entry<String, Object> entry : map.entrySet()) {
         result.put(
             entry.getKey(),

google-cloud-firestore/src/test/java/com/google/cloud/firestore/DocumentReferenceTest.java

@@ -24,6 +24,8 @@
 import static com.google.cloud.firestore.LocalFirestoreHelper.DOCUMENT_NAME;
 import static com.google.cloud.firestore.LocalFirestoreHelper.DOCUMENT_PATH;
 import static com.google.cloud.firestore.LocalFirestoreHelper.FIELD_TRANSFORM_COMMIT_RESPONSE;
+import static com.google.cloud.firestore.LocalFirestoreHelper.FOO_LIST;
+import static com.google.cloud.firestore.LocalFirestoreHelper.FOO_MAP;
 import static com.google.cloud.firestore.LocalFirestoreHelper.GEO_POINT;
 import static com.google.cloud.firestore.LocalFirestoreHelper.NESTED_CLASS_OBJECT;
 import static com.google.cloud.firestore.LocalFirestoreHelper.SERVER_TIMESTAMP_PROTO;
@@ -69,10 +71,13 @@
 import com.google.cloud.firestore.LocalFirestoreHelper.InvalidPOJO;
 import com.google.cloud.firestore.spi.v1.FirestoreRpc;
 import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableMap;
+import com.google.firestore.v1.ArrayValue;
 import com.google.firestore.v1.BatchGetDocumentsRequest;
 import com.google.firestore.v1.BatchGetDocumentsResponse;
 import com.google.firestore.v1.CommitRequest;
 import com.google.firestore.v1.CommitResponse;
+import com.google.firestore.v1.MapValue;
 import com.google.firestore.v1.Value;
 import java.math.BigInteger;
 import java.util.ArrayList;
@@ -1073,4 +1078,66 @@ public void deleteNestedFieldUsingFieldPath() throws Exception {
                 Collections.<String, Value>emptyMap(), Collections.singletonList("`a.b`.`c.d`")));
     assertEquals(expectedCommit, commitCapture.getValue());
   }
+
+  @Test
+  public void deserializeCustomList() throws ExecutionException, InterruptedException {
+    ImmutableMap CUSTOM_LIST_PROTO =
+        ImmutableMap.<String, Value>builder()
+            .put(
+                "fooList",
+                Value.newBuilder()
+                    .setArrayValue(
+                        ArrayValue.newBuilder()
+                            .addValues(
+                                Value.newBuilder()
+                                    .setMapValue(
+                                        MapValue.newBuilder().putAllFields(SINGLE_FIELD_PROTO))
+                                    .build()))
+                    .build())
+            .build();
+    doAnswer(getAllResponse(CUSTOM_LIST_PROTO))
+        .when(firestoreMock)
+        .streamRequest(
+            getAllCapture.capture(),
+            streamObserverCapture.capture(),
+            Matchers.<ServerStreamingCallable>any());
+    DocumentSnapshot snapshot = documentReference.get().get();
+    LocalFirestoreHelper.CustomList customList =
+        snapshot.toObject(LocalFirestoreHelper.CustomList.class);
+
+    assertEquals(FOO_LIST, customList.fooList);
+    assertEquals(SINGLE_FIELD_OBJECT, customList.fooList.get(0));
+  }
+
+  @Test
+  public void deserializeCustomMap() throws ExecutionException, InterruptedException {
+    ImmutableMap CUSTOM_MAP_PROTO =
+        ImmutableMap.<String, Value>builder()
+            .put(
+                "fooMap",
+                Value.newBuilder()
+                    .setMapValue(
+                        MapValue.newBuilder()
+                            .putFields(
+                                "customMap",
+                                Value.newBuilder()
+                                    .setMapValue(
+                                        MapValue.newBuilder().putAllFields(SINGLE_FIELD_PROTO))
+                                    .build())
+                            .build())
+                    .build())
+            .build();
+    doAnswer(getAllResponse(CUSTOM_MAP_PROTO))
+        .when(firestoreMock)
+        .streamRequest(
+            getAllCapture.capture(),
+            streamObserverCapture.capture(),
+            Matchers.<ServerStreamingCallable>any());
+    DocumentSnapshot snapshot = documentReference.get().get();
+    LocalFirestoreHelper.CustomMap customMap =
+        snapshot.toObject(LocalFirestoreHelper.CustomMap.class);
+
+    assertEquals(FOO_MAP, customMap.fooMap);
+    assertEquals(SINGLE_FIELD_OBJECT, customMap.fooMap.get("customMap"));
+  }
 }

google-cloud-firestore/src/test/java/com/google/cloud/firestore/LocalFirestoreHelper.java

@@ -143,6 +143,8 @@ public final class LocalFirestoreHelper {
   public static final Timestamp TIMESTAMP;
   public static final GeoPoint GEO_POINT;
   public static final Blob BLOB;
+  public static final FooList<SingleField> FOO_LIST = new FooList<>();
+  public static final FooMap<String, SingleField> FOO_MAP = new FooMap<>();
 
   public static final Precondition UPDATE_PRECONDITION;
 
@@ -165,6 +167,30 @@ public boolean equals(Object o) {
     }
   }
 
+  public static class FooList<E> extends ArrayList<SingleField> {
+    public FooList() {
+      super();
+    }
+  }
+
+  public static class CustomList {
+    public CustomList() {}
+
+    public FooList<SingleField> fooList;
+  }
+
+  public static class FooMap<K, V> extends HashMap<K, V> {
+    public FooMap() {
+      super();
+    }
+  }
+
+  public static class CustomMap {
+    public CustomMap() {}
+
+    public FooMap<String, SingleField> fooMap;
+  }
+
   public static class NestedClass {
     public SingleField first = new SingleField();
     public AllSupportedTypes second = new AllSupportedTypes();
@@ -773,6 +799,8 @@ public boolean equals(Object o) {
     SINGLE_FIELD_MAP = map("foo", (Object) "bar");
     SINGLE_FILED_MAP_WITH_DOT = map("c.d", (Object) "bar");
     SINGLE_FIELD_OBJECT = new SingleField();
+    FOO_LIST.add(SINGLE_FIELD_OBJECT);
+    FOO_MAP.put("customMap", SINGLE_FIELD_OBJECT);
     SINGLE_FIELD_PROTO = map("foo", Value.newBuilder().setStringValue("bar").build());
     UPDATED_POJO_PROTO =
         map(

google-cloud-firestore/src/test/java/com/google/cloud/firestore/it/ITSystemTest.java

@@ -16,6 +16,8 @@
 
 package com.google.cloud.firestore.it;
 
+import static com.google.cloud.firestore.LocalFirestoreHelper.FOO_LIST;
+import static com.google.cloud.firestore.LocalFirestoreHelper.FOO_MAP;
 import static com.google.cloud.firestore.LocalFirestoreHelper.UPDATE_SINGLE_FIELD_OBJECT;
 import static com.google.cloud.firestore.LocalFirestoreHelper.map;
 import static com.google.common.truth.Truth.assertThat;
@@ -1402,6 +1404,34 @@ public Void updateCallback(Transaction transaction) throws Exception {
     }
   }
 
+  @Test
+  public void deserializeCustomList() throws Exception {
+    LocalFirestoreHelper.CustomList customList = new LocalFirestoreHelper.CustomList();
+    customList.fooList = FOO_LIST;
+    DocumentReference documentReference = randomColl.document("doc1");
+    documentReference.set(customList).get();
+    DocumentSnapshot documentSnapshots = documentReference.get().get();
+    LocalFirestoreHelper.CustomList targetCustomList =
+        documentSnapshots.toObject(LocalFirestoreHelper.CustomList.class);
+
+    assertEquals(FOO_LIST, targetCustomList.fooList);
+    assertEquals(SINGLE_FIELD_OBJECT, targetCustomList.fooList.get(0));
+  }
+
+  @Test
+  public void deserializeCustomMap() throws Exception {
+    LocalFirestoreHelper.CustomMap customMap = new LocalFirestoreHelper.CustomMap();
+    customMap.fooMap = FOO_MAP;
+    DocumentReference documentReference = randomColl.document("doc1");
+    documentReference.set(customMap).get();
+    DocumentSnapshot documentSnapshots = documentReference.get().get();
+    LocalFirestoreHelper.CustomMap targetCustomMap =
+        documentSnapshots.toObject(LocalFirestoreHelper.CustomMap.class);
+
+    assertEquals(FOO_MAP, targetCustomMap.fooMap);
+    assertEquals(SINGLE_FIELD_OBJECT, targetCustomMap.fooMap.get("customMap"));
+  }
+
   /** Wrapper around ApiStreamObserver that returns the results in a list. */
   private static class StreamConsumer<T> implements ApiStreamObserver<T> {
     SettableApiFuture<List<T>> done = SettableApiFuture.create();