schematype(UUID): added null check to prevent error on binaryToString conversion

lib/schema/uuid.js

@@ -23,7 +23,7 @@ const Binary = MongooseBuffer.Binary;
 
 function hex2buffer(hex) {
   // use buffer built-in function to convert from hex-string to buffer
-  const buff = hex && Buffer.from(hex, 'hex');
+  const buff = hex != null && Buffer.from(hex, 'hex');
   return buff;
 }
 
@@ -36,7 +36,7 @@ function hex2buffer(hex) {
 
 function binary2hex(buf) {
   // use buffer built-in function to convert from buffer to hex-string
-  const hex = buf && buf.toString('hex');
+  const hex = buf != null && buf.toString('hex');
   return hex;
 }
 
@@ -66,8 +66,9 @@ function stringToBinary(uuidStr) {
  */
 function binaryToString(uuidBin) {
   // i(hasezoey) dont quite know why, but "uuidBin" may sometimes also be the already processed string
-  if (uuidBin && typeof uuidBin !== 'string') {
-    const hex = binary2hex(uuidBin);
+  let hex;
+  if (typeof uuidBin !== 'string' && uuidBin != null) {
+    hex = binary2hex(uuidBin);
     const uuidStr = hex.substring(0, 8) + '-' + hex.substring(8, 8 + 4) + '-' + hex.substring(12, 12 + 4) + '-' + hex.substring(16, 16 + 4) + '-' + hex.substring(20, 20 + 12);
     return uuidStr;
   }

test/schema.uuid.test.js

@@ -10,6 +10,8 @@ const assert = require('assert');
 const mongoose = start.mongoose;
 const Schema = mongoose.Schema;
 
+const { v4: uuidv4 } = require('uuid');
+
 describe('SchemaUUID', function() {
   let Model;
   let TestSchema;
@@ -101,6 +103,32 @@ describe('SchemaUUID', function() {
     assert.strictEqual(foundDocAll[0].y[2], '5b544b71-8988-422b-a4df-bf691939fe4e');
   });
 
+  it('should not convert to string nullish UUIDs (gh-13032)', async function() {
+    const schema = new Schema({
+      _id: {
+        type: Schema.Types.UUID,
+        default: uuidv4(),
+        immutable: true
+      },
+      name: {
+        type: String,
+        required: true
+      },
+      organization: {
+        type: Schema.Types.UUID,
+        ref: 'Organization',
+        index: true
+      }
+    }, { _id: false });
+
+    const Test = db.model('gh_13032', schema);
+
+    const { name, organization } = await Test.create({ name: 'test' });
+
+    assert.equal(name, 'test');
+    assert.equal(organization, undefined);
+  });
+
   // the following are TODOs based on SchemaUUID.prototype.$conditionalHandlers which are not tested yet
   it('should work with $bits* operators');
   it('should work with $all operator');