fix(EJSON): export the result of optionally requiring EJSON

Optionally require and export EJSON from core for use in native's APM logging feature.

Author: rweinberger

Diff for: index.js

@@ -2,6 +2,7 @@
 
 var BSON = require('bson');
 var require_optional = require('require_optional');
+const EJSON = require('./lib/utils').retrieveEJSON();
 
 try {
   // Attempt to grab the native BSON parser
@@ -31,6 +32,7 @@ module.exports = {
   ReadPreference: require('./lib/topologies/read_preference'),
   Sessions: require('./lib/sessions'),
   BSON: BSON,
+  EJSON: EJSON,
   // Raw operations
   Query: require('./lib/connection/commands').Query,
   // Auth mechanisms

Diff for: lib/utils.js

@@ -48,6 +48,30 @@ try {
   console.warn(err.message);
 }
 
+// Throw an error if an attempt to use EJSON is made when it is not installed
+const noEJSONError = function() {
+  throw new Error('The `mongodb-extjson` package was not found. Please install it and try again.');
+};
+
+// Facilitate loading EJSON optionally
+const retrieveEJSON = function() {
+  let EJSON = null;
+  try {
+    EJSON = requireOptional('mongodb-extjson');
+  } catch (error) {} // eslint-disable-line
+  if (!EJSON) {
+    EJSON = {
+      parse: noEJSONError,
+      deserialize: noEJSONError,
+      serialize: noEJSONError,
+      stringify: noEJSONError,
+      setBSONModule: noEJSONError,
+      BSON: noEJSONError
+    };
+  }
+  return EJSON;
+};
+
 /*
  * Checks that collation is supported by server.
  *
@@ -66,5 +90,6 @@ module.exports = {
   relayEvents,
   Kerberos,
   MongoAuthProcess,
-  collationNotSupported
+  collationNotSupported,
+  retrieveEJSON
 };

Diff for: package.json

@@ -40,6 +40,7 @@
   },
   "peerOptionalDependencies": {
     "kerberos": ">= 0.0.23 < 1.0.0",
+    "mongodb-extjson": "^2.1.2",
     "snappy": "^6.0.1",
     "bson-ext": "^2.0.0"
   },