Decrement the level of BsonWriter after checking _id in

IdHoldingBsonWriter.writeEndArray

JAVA-3622

Author: jstewart148

driver-core/src/main/com/mongodb/internal/connection/IdHoldingBsonWriter.java

@@ -127,15 +127,14 @@ public void writeStartArray(final String name) {
 
     @Override
     public void writeEndArray() {
-        super.writeEndArray();
-
         if (isWritingId()) {
             getIdBsonWriter().writeEndArray();
             if (getIdBsonWriter().getCurrentLevel() == 0) {
                 getIdBsonWriter().writeEndDocument();
                 id = new RawBsonDocument(getBytes()).get(ID_FIELD_NAME);
             }
         }
+        super.writeEndArray();
     }
 
     @Override

driver-core/src/test/unit/com/mongodb/internal/connection/IdHoldingBsonWriterSpecification.groovy

@@ -16,9 +16,11 @@
 
 package com.mongodb.internal.connection
 
+import org.bson.BsonArray
 import org.bson.BsonBinaryReader
 import org.bson.BsonBinaryWriter
 import org.bson.BsonDocument
+import org.bson.BsonObjectId
 import org.bson.codecs.BsonDocumentCodec
 import org.bson.codecs.DecoderContext
 import org.bson.codecs.EncoderContext
@@ -72,6 +74,20 @@ class IdHoldingBsonWriterSpecification extends Specification {
         id << getBsonValues()
     }
 
+    def 'serialize document with list of documents that contain an _id field'() {
+        def bsonBinaryWriter = new BsonBinaryWriter(new BasicOutputBuffer())
+        def idTrackingBsonWriter = new IdHoldingBsonWriter(bsonBinaryWriter)
+        def document = new BsonDocument('_id', new BsonObjectId())
+                .append('items', new BsonArray(Collections.singletonList(new BsonDocument('_id', new BsonObjectId()))))
+
+        when:
+        new BsonDocumentCodec().encode(idTrackingBsonWriter, document, EncoderContext.builder().build())
+        def encodedDocument = getEncodedDocument(bsonBinaryWriter.getBsonOutput())
+
+        then:
+        encodedDocument == document
+    }
+
     private static BsonDocument getEncodedDocument(BsonOutput buffer) {
         new BsonDocumentCodec().decode(new BsonBinaryReader(buffer.getByteBuffers().get(0).asNIO()),
                 DecoderContext.builder().build())