fix(model): avoid saving applied defaults if path is deselected

lib/helpers/projection/isPathExcluded.js

@@ -12,6 +12,10 @@ const isDefiningProjection = require('./isDefiningProjection');
  */
 
 module.exports = function isPathExcluded(projection, path) {
+  if (projection == null) {
+    return false;
+  }
+
   if (path === '_id') {
     return projection._id === 0;
   }

lib/model.js

@@ -51,11 +51,13 @@ const {
   getRelatedDBIndexes,
   getRelatedSchemaIndexes
 } = require('./helpers/indexes/getRelatedIndexes');
+const isPathExcluded = require('./helpers/projection/isPathExcluded');
 const decorateDiscriminatorIndexOptions = require('./helpers/indexes/decorateDiscriminatorIndexOptions');
 const isPathSelectedInclusive = require('./helpers/projection/isPathSelectedInclusive');
 const leanPopulateMap = require('./helpers/populate/leanPopulateMap');
 const modifiedPaths = require('./helpers/update/modifiedPaths');
 const parallelLimit = require('./helpers/parallelLimit');
+const parentPaths = require('./helpers/path/parentPaths');
 const prepareDiscriminatorPipeline = require('./helpers/aggregate/prepareDiscriminatorPipeline');
 const pushNestedArrayPaths = require('./helpers/model/pushNestedArrayPaths');
 const removeDeselectedForeignField = require('./helpers/populate/removeDeselectedForeignField');
@@ -760,6 +762,19 @@ Model.prototype.$__delta = function() {
       }
     }
 
+    // If this path is set to default, and either this path or one of
+    // its parents is excluded, don't treat this path as dirty.
+    if (this.$isDefault(data.path) && this.$__.selected) {
+      if (data.path.indexOf('.') === -1 && isPathExcluded(this.$__.selected, data.path)) {
+        continue;
+      }
+
+      const pathsToCheck = parentPaths(data.path);
+      if (pathsToCheck.find(path => isPathExcluded(this.$__.isSelected, path))) {
+        continue;
+      }
+    }
+
     if (divergent.length) continue;
     if (value === undefined) {
       operand(this, where, delta, data, 1, '$unset');
@@ -798,6 +813,11 @@ Model.prototype.$__delta = function() {
   if (this.$__.version) {
     this.$__version(where, delta);
   }
+
+  if (Object.keys(delta).length === 0) {
+    return [where, null];
+  }
+
   return [where, delta];
 };