GODRIVER-1600 Add support for hidden index option (#400)

Author: Divjot Arora

mongo/index_view.go

@@ -334,6 +334,9 @@ func (iv IndexView) createOptionsDoc(opts *options.IndexOptions) (bsoncore.Docum
 
 		optsDoc = bsoncore.AppendDocumentElement(optsDoc, "wildcardProjection", doc)
 	}
+	if opts.Hidden != nil {
+		optsDoc = bsoncore.AppendBooleanElement(optsDoc, "hidden", *opts.Hidden)
+	}
 
 	return optsDoc, nil
 }

mongo/integration/index_view_test.go

@@ -136,6 +136,24 @@ func TestIndexView(t *testing.T) {
 				})
 			})
 		})
+		mt.RunOpts("hidden", mtest.NewOptions().MinServerVersion("4.4"), func(mt *mtest.T) {
+			iv := mt.Coll.Indexes()
+			keysDoc := bson.D{{"x", int32(1)}}
+			model := mongo.IndexModel{
+				Keys:    keysDoc,
+				Options: options.Index().SetHidden(true),
+			}
+
+			_, err := iv.CreateOne(mtest.Background, model)
+			assert.Nil(mt, err, "CreateOne error: %v", err)
+
+			indexDoc := getIndexDoc(mt, iv, keysDoc)
+			assert.NotNil(mt, indexDoc, "index with keys document %v was not found", keysDoc)
+			checkIndexDocContains(mt, indexDoc, bson.E{
+				Key:   "hidden",
+				Value: true,
+			})
+		})
 		mt.Run("nil keys", func(mt *mtest.T) {
 			_, err := mt.Coll.Indexes().CreateOne(mtest.Background, mongo.IndexModel{
 				Keys: nil,

mongo/options/indexoptions.go

@@ -249,6 +249,10 @@ type IndexOptions struct {
 
 	// A document that defines the wildcard projection for the index.
 	WildcardProjection interface{}
+
+	// If true, the index will exist on the target collection but will not be used by the query planner when executing
+	// operations. This option is only valid for MongoDB versions >= 4.4. The default value is false.
+	Hidden *bool
 }
 
 // Index creates a new IndexOptions instance.
@@ -370,6 +374,12 @@ func (i *IndexOptions) SetWildcardProjection(wildcardProjection interface{}) *In
 	return i
 }
 
+// SetHidden sets the value for the Hidden field.
+func (i *IndexOptions) SetHidden(hidden bool) *IndexOptions {
+	i.Hidden = &hidden
+	return i
+}
+
 // MergeIndexOptions combines the given IndexOptions into a single IndexOptions in a last-one-wins fashion.
 func MergeIndexOptions(opts ...*IndexOptions) *IndexOptions {
 	i := Index()
@@ -432,6 +442,9 @@ func MergeIndexOptions(opts ...*IndexOptions) *IndexOptions {
 		if opt.WildcardProjection != nil {
 			i.WildcardProjection = opt.WildcardProjection
 		}
+		if opt.Hidden != nil {
+			i.Hidden = opt.Hidden
+		}
 	}
 
 	return i