fix(discriminators): remove fields not selected in child when queryin…

…g by base model

Fix #4991

lib/document.js

@@ -373,6 +373,13 @@ function init(self, obj, doc, prefix) {
     path = prefix + i;
     schema = self.schema.path(path);
 
+    // Should still work if not a model-level discriminator, but should not be
+    // necessary. This is *only* to catch the case where we queried using the
+    // base model and the discriminated model has a projection
+    if (self.schema.$isRootDiscriminator && !self.isSelected(path)) {
+      return;
+    }
+
     if (!schema && utils.isObject(obj[i]) &&
         (!obj[i].constructor || utils.getFunctionName(obj[i].constructor) === 'Object')) {
       // assume nested object

lib/model.js

@@ -838,6 +838,8 @@ Model.discriminator = function(name, schema) {
     _name = name;
   }
 
+  schema.$isRootDiscriminator = true;
+
   this.discriminators[_name] = this.db.model(name, schema, this.collection.name);
   var d = this.discriminators[_name];
   d.prototype.__proto__ = this.prototype;

lib/queryhelpers.js

@@ -60,7 +60,10 @@ exports.createModel = function createModel(model, doc, fields) {
     : null;
 
   if (key && doc[key] && model.discriminators && model.discriminators[doc[key]]) {
-    return new model.discriminators[doc[key]](undefined, fields, true);
+    var discriminator = model.discriminators[doc[key]];
+    var _fields = utils.clone(fields);
+    exports.applyPaths(_fields, discriminator.schema);
+    return new model.discriminators[doc[key]](undefined, _fields, true);
   }
 
   return new model(undefined, fields, true);

lib/schema/documentarray.js

@@ -338,18 +338,26 @@ function scopePaths(array, fields, init) {
     return undefined;
   }
 
-  var path = array.path + '.',
-      keys = Object.keys(fields),
-      i = keys.length,
-      selected = {},
-      hasKeys,
-      key;
+  var path = array.path + '.';
+  var keys = Object.keys(fields);
+  var i = keys.length;
+  var selected = {};
+  var hasKeys;
+  var key;
+  var sub;
 
   while (i--) {
     key = keys[i];
     if (key.indexOf(path) === 0) {
+      sub = key.substring(path.length);
+      if (sub === '$') {
+        continue;
+      }
+      if (sub.indexOf('$.') === 0) {
+        sub = sub.substr(2);
+      }
       hasKeys || (hasKeys = true);
-      selected[key.substring(path.length)] = fields[key];
+      selected[sub] = fields[key];
     }
   }
 

test/schema.select.test.js

@@ -162,6 +162,7 @@ describe('schema select option', function() {
             assert.equal(s.isSelected('thin'), true);
             assert.equal(s.isSelected('docs.name'), false);
             assert.equal(s.isSelected('docs.bool'), true);
+            assert.ok(s.isSelected('docs'));
             assert.strictEqual(undefined, s.name);
             assert.strictEqual(undefined, s.docs[0].name);
             assert.equal(s.thin, true);