fix: Throw error on bigint usage and add helpers to Long (#426)

Adds helpers toBigInt and fromBigInt to the Long class to help
support 64bit values. Throws an error when bigint is attempted to
be serialized.

NODE-2378

lib/bson/long.js

@@ -77,6 +77,11 @@ Long.prototype.toNumber = function() {
   return this.high_ * Long.TWO_PWR_32_DBL_ + this.getLowBitsUnsigned();
 };
 
+/** Converts the Long to a BigInt (arbitrary precision). */
+Long.prototype.toBigInt = function () {
+  return BigInt(this.toString());
+}
+
 /**
  * Return the JSON value.
  *
@@ -711,6 +716,15 @@ Long.fromNumber = function(value) {
   }
 };
 
+/**
+ * Returns a Long representing the given value, provided that it is a finite number. Otherwise, zero is returned.
+ * @param {bigint} value - The number in question
+ * @returns {Long} The corresponding Long value
+ */
+Long.fromBigInt =  function(value) {
+  return Long.fromString(value.toString(10), 10);
+}
+
 /**
  * Returns a Long representing the 64-bit integer that comes by concatenating the given high and low bits. Each is assumed to use 32 bits.
  *

lib/bson/parser/serializer.js

@@ -709,6 +709,8 @@ var serializeInto = function serializeInto(
         index = serializeString(buffer, key, value, index, true);
       } else if (type === 'number') {
         index = serializeNumber(buffer, key, value, index, true);
+      } else  if(type === 'bigint') {
+        throw new TypeError('Unsupported type BigInt, please use Decimal128');
       } else if (type === 'boolean') {
         index = serializeBoolean(buffer, key, value, index, true);
       } else if (value instanceof Date || isDate(value)) {
@@ -820,6 +822,8 @@ var serializeInto = function serializeInto(
         index = serializeString(buffer, key, value, index);
       } else if (type === 'number') {
         index = serializeNumber(buffer, key, value, index);
+      } else if(type === 'bigint') {
+        throw new TypeError('Unsupported type BigInt, please use Decimal128');
       } else if (type === 'boolean') {
         index = serializeBoolean(buffer, key, value, index);
       } else if (value instanceof Date || isDate(value)) {
@@ -923,6 +927,8 @@ var serializeInto = function serializeInto(
         index = serializeString(buffer, key, value, index);
       } else if (type === 'number') {
         index = serializeNumber(buffer, key, value, index);
+      } else if(type === 'bigint') {
+        throw new TypeError('Unsupported type BigInt, please use Decimal128');
       } else if (type === 'boolean') {
         index = serializeBoolean(buffer, key, value, index);
       } else if (value instanceof Date || isDate(value)) {

test/node/bigint_test.js

@@ -0,0 +1,59 @@
+/* globals BigInt */
+'use strict';
+
+var createBSON = require('../utils');
+var BSON = require('../..');
+var bson = createBSON();
+
+try {
+  BigInt(0);
+
+  // will throw on the line above if BigInt is not supported in the runtime
+
+  exports['Should error on serialize bigint'] = function (test) {
+    var testDoc = { b: BigInt(32) };
+    try {
+      bson.serialize(testDoc)
+      test.ok(false);
+    } catch (error) {
+      test.ok(error instanceof TypeError);
+      test.ok(error.message === 'Unsupported type BigInt, please use Decimal128');
+    }
+    test.done();
+  };
+
+  exports['Should error on serialize bigint inside array'] = function (test) {
+    var testDoc = { b: [0, 1, BigInt(0x1ffffffff)] };
+    try {
+      bson.serialize(testDoc)
+      test.ok(false);
+    } catch (error) {
+      test.ok(error instanceof TypeError);
+      test.ok(error.message === 'Unsupported type BigInt, please use Decimal128');
+    }
+    test.done();
+  };
+
+  exports['Should error on serialize bigint inside subdocument'] = function (test) {
+    var testDoc = { b: { a: BigInt(0x1ffffffff) } };
+    try {
+      bson.serialize(testDoc)
+      test.ok(false);
+    } catch (error) {
+      test.ok(error instanceof TypeError);
+      test.ok(error.message === 'Unsupported type BigInt, please use Decimal128');
+    }
+    test.done();
+  };
+
+  exports['Should support conversion on Long type'] = function (test) {
+    var long = BSON.Long.fromBigInt(BigInt(200));
+    test.ok(long._bsontype === 'Long');
+    test.ok(long.toNumber() === 200);
+    test.ok(long.toBigInt() === BigInt(200));
+    test.done();
+  }
+
+} catch (_) {
+  // 'JS VM does not support BigInt'
+}