fix: cleanup and tests for #15725

Author: vkarpov15

lib/types/documentArray/methods/index.js

@@ -137,11 +137,9 @@ const methods = {
       idSchemaType = schemaType.schema.path('_id');
     } else if (schemaType && schemaType.casterConstructor && schemaType.casterConstructor.schema) {
       idSchemaType = schemaType.casterConstructor.schema.path('_id');
-    } else if (this.length > 0 && this[0] != null && this[0].$__schema) {
-      idSchemaType = this[0].$__schema.path('_id');
     }
 
-    let castedId = id;
+    let castedId = null;
     if (idSchemaType) {
       try {
         castedId = idSchemaType.cast(id);
@@ -150,7 +148,6 @@ const methods = {
       }
     }
 
-    let sid;
     let _id;
 
     for (const val of this) {
@@ -160,24 +157,20 @@ const methods = {
 
       _id = val.get('_id');
 
-      if (_id === null || typeof _id === 'undefined') {
+      if (_id == null) {
         continue;
       } else if (_id instanceof Document) {
-        sid || (sid = String(id));
-        if (sid == _id._id) {
+        _id = _id.get('_id');
+        if (castedId != null && utils.deepEqual(castedId, _id)) {
           return val;
-        }
-      } else if (castedId != null && !isBsonType(castedId, 'ObjectId') && !isBsonType(_id, 'ObjectId')) {
-        if (castedId == _id || utils.deepEqual(castedId, _id)) {
-          return val;
-        }
-      } else if (castedId != null && isBsonType(castedId, 'ObjectId') && isBsonType(_id, 'ObjectId')) {
-        if (castedId.toString() === _id.toString()) {
+        } else if (castedId == null && (id == _id || utils.deepEqual(id, _id))) {
+          // Backwards compat: compare user-specified param to _id using loose equality
           return val;
         }
-      } else if (castedId != null && castedId == _id) {
+      } else if (castedId != null && utils.deepEqual(castedId, _id)) {
         return val;
-      } else if (castedId == null && (id == _id || utils.deepEqual(id, _id))) {
+      } else if (castedId == null && (_id == id || utils.deepEqual(id, _id))) {
+        // Backwards compat: compare user-specified param to _id using loose equality
         return val;
       }
     }

test/types.documentarray.test.js

@@ -83,7 +83,7 @@ describe('types.documentarray', function() {
     sub1.title = 'Hello again to all my friends';
     let id = sub1.id;
 
-    let a = new MongooseDocumentArray([sub1]);
+    let a = new MongooseDocumentArray([sub1], 'test', null);
     assert.equal(a.id(id).title, 'Hello again to all my friends');
     assert.equal(a.id(sub1._id).title, 'Hello again to all my friends');
 
@@ -186,8 +186,23 @@ describe('types.documentarray', function() {
 
     a = new MongooseDocumentArray([sub]);
     assert.equal(a.id(id).title, 'Hello again to all my friends');
+  });
+
+  it('#id with custom schematype (gh-15725)', function() {
+    const schema = new Schema({ _id: Number, name: String });
+    const Subdocument = TestDoc(schema);
+
+    const sub1 = new Subdocument();
+    sub1._id = 42;
+    sub1.title = 'Hello again to all my friends';
 
+    const parentDoc = { $__: true, $__schema: new Schema({ subdocs: [schema] }) };
 
+    const a = new MongooseDocumentArray([sub1], 'test', parentDoc);
+    assert.equal(a.id('42').title, 'Hello again to all my friends');
+    assert.equal(a.id(sub1.id).title, 'Hello again to all my friends');
+    assert.ok(!a.id('43'));
+    assert.ok(!a.id('not a number'));
   });
 
   describe('inspect', function() {