Skip unknown fields while decoding FieldValue proto objects. (#1354)

3 files changed, 40 insertions, 17 deletions

diff --git a/Firestore/core/src/firebase/firestore/nanopb/reader.cc b/Firestore/core/src/firebase/firestore/nanopb/reader.cc
index ec4282d..69e3d83 100644
--- a/Firestore/core/src/firebase/firestore/nanopb/reader.cc
+++ b/Firestore/core/src/firebase/firestore/nanopb/reader.cc
@@ -136,6 +136,14 @@ std::string Reader::ReadString() {
   return result;
 }
 
+void Reader::SkipField(const Tag& tag) {
+  if (!status_.ok()) return;
+
+  if (!pb_skip_field(&stream_, tag.wire_type)) {
+    status_ = Status(FirestoreErrorCode::DataLoss, PB_GET_ERROR(&stream_));
+  }
+}
+
 }  // namespace nanopb
 }  // namespace firestore
 }  // namespace firebase
diff --git a/Firestore/core/src/firebase/firestore/nanopb/reader.h b/Firestore/core/src/firebase/firestore/nanopb/reader.h
index 930211a..2c16ec4 100644
--- a/Firestore/core/src/firebase/firestore/nanopb/reader.h
+++ b/Firestore/core/src/firebase/firestore/nanopb/reader.h
@@ -89,6 +89,15 @@ class Reader {
   template <typename T>
   T ReadNestedMessage(const std::function<T(Reader*)>& read_message_fn);
 
+  /**
+   * Discards the bytes associated with the given tag.
+   *
+   * @param tag The tag associated with the field that is otherwise about to be
+   * read. This method uses the tag to determine how many bytes should be
+   * discarded.
+   */
+  void SkipField(const Tag& tag);
+
   size_t bytes_left() const {
     return stream_.bytes_left;
   }
diff --git a/Firestore/core/src/firebase/firestore/remote/serializer.cc b/Firestore/core/src/firebase/firestore/remote/serializer.cc
index 0839efc..eee56f8 100644
--- a/Firestore/core/src/firebase/firestore/remote/serializer.cc
+++ b/Firestore/core/src/firebase/firestore/remote/serializer.cc
@@ -204,20 +204,20 @@ FieldValue DecodeFieldValueImpl(Reader* reader) {
         }
         break;
 
-      default:
-        // We could get here for one of two reasons; either because the input
-        // bytes are corrupt, or because we're attempting to parse a tag that we
-        // haven't implemented yet. Long term, the latter reason should become
-        // less likely (especially in production), so we'll assume former.
-
-        // TODO(rsgowman): While still in development, we'll contradict the
-        // above and assume the latter. Remove the following assertion when
-        // we're confident that we're handling all the tags in the protos.
+      case google_firestore_v1beta1_Value_double_value_tag:
+      case google_firestore_v1beta1_Value_bytes_value_tag:
+      case google_firestore_v1beta1_Value_reference_value_tag:
+      case google_firestore_v1beta1_Value_geo_point_value_tag:
+      case google_firestore_v1beta1_Value_array_value_tag:
+        // TODO(b/74243929): Implement remaining types.
         HARD_FAIL("Unhandled message field number (tag): %i.",
                   tag.field_number);
-        reader->set_status(Status(
-            FirestoreErrorCode::DataLoss,
-            "Input proto bytes cannot be parsed (invalid field number (tag))"));
+
+      default:
+        // Unknown tag. According to the proto spec, we need to ignore these. No
+        // action required here, though we'll need to skip the relevant bytes
+        // below.
+        break;
     }
 
     if (!reader->status().ok()) return FieldValue::NullValue();
@@ -247,12 +247,18 @@ FieldValue DecodeFieldValueImpl(Reader* reader) {
             reader->ReadNestedMessage<ObjectValue::Map>(DecodeMapValue));
         break;
 
+      case google_firestore_v1beta1_Value_double_value_tag:
+      case google_firestore_v1beta1_Value_bytes_value_tag:
+      case google_firestore_v1beta1_Value_reference_value_tag:
+      case google_firestore_v1beta1_Value_geo_point_value_tag:
+      case google_firestore_v1beta1_Value_array_value_tag:
+        // TODO(b/74243929): Implement remaining types.
+        HARD_FAIL("Unhandled message field number (tag): %i.",
+                  tag.field_number);
+
       default:
-        // This indicates an internal error as we've already ensured that this
-        // is a valid field_number.
-        HARD_FAIL(
-            "Somehow got an unexpected field number (tag) after verifying that "
-            "the field number was expected.");
+        // Unknown tag. According to the proto spec, we need to ignore these.
+        reader->SkipField(tag);
     }
   }