chore: boron node version test failures (#2747)

Author: nbbeeken

lib/db.js

@@ -440,7 +440,7 @@ Db.prototype.collection = function(name, options, callback) {
   }
 
   // Merge in all needed options and ensure correct writeConcern merging from db level
-  options = conditionallyMergeWriteConcern(options, this.s.options, COLLECTION_OPTION_KEYS, true);
+  options = conditionallyMergeWriteConcern(options, this.s.options);
 
   // Execute
   if (options == null || !options.strict) {

lib/utils.js

@@ -533,8 +533,11 @@ function decorateWithExplain(command, explain) {
   return { explain: command, verbosity: explain.verbosity };
 }
 
+const nodejsMajorVersion = +process.version.split('.')[0].substring(1);
 const emitProcessWarning = msg =>
-  process.emitWarning(msg, { type: 'DeprecationWarning', code: MONGODB_WARNING_CODE });
+  nodejsMajorVersion <= 6
+    ? process.emitWarning(msg, 'DeprecationWarning', MONGODB_WARNING_CODE)
+    : process.emitWarning(msg, { type: 'DeprecationWarning', code: MONGODB_WARNING_CODE });
 // eslint-disable-next-line no-console
 const emitConsoleWarning = msg => console.error(msg);
 const emitDeprecationWarning = process.emitWarning ? emitProcessWarning : emitConsoleWarning;
@@ -836,7 +839,9 @@ const MONGODB_WARNING_CODE = 'MONGODB DRIVER';
  */
 function emitWarning(message) {
   if (process.emitWarning) {
-    return process.emitWarning(message, { code: MONGODB_WARNING_CODE });
+    return nodejsMajorVersion <= 6
+      ? process.emitWarning(message, undefined, MONGODB_WARNING_CODE)
+      : process.emitWarning(message, { code: MONGODB_WARNING_CODE });
   } else {
     // Approximate the style of print out on node versions pre 8.x
     // eslint-disable-next-line no-console